Development of Oral Tablets Containing Nicorandil

Miguel António Pires de Matos Development of oral tablets containing Nicorandil Dissertação do 2º Ciclo de Estudos conducente ao grau de Mestre em Tecnologia Farmacêutica Trabalho realizado sob a orientação do Professor Doutor Domingos Ferreira e Professor Doutor Sérgio Simões Outubro 2014 ii Disclaimer The partial reproduction of this thesis is authorized for research purposes only, by written declaration of the author, to which is committed. iii Acknowledgments Agradeço aos meus orientadores Professor Doutor Domingos Ferreira e Professor Doutor Sérgio Simões toda a ajuda e apoio prestados. Um muito obrigado ao Professor Doutor Paulo Costa pela disponibilidade, comentários e ajuda. Este trabalho contou com a colaboração da Bluepharma, Indústria Farmacêutica S.A. que disponibilizou as suas instalações, equipamentos e recursos para a execução do trabalho experimental. Deixo um reconhecimento sentido pela colaboração, ajuda e sobretudo paciência, aos meus colegas, Alice Urbano, José Miguel, Patrícia Silva, Paulo Antunes e Sílvia Vicente. Agradeço, de forma especial, à Cláudia Silva, pela amizade. Para a minha família, pelo apoio de toda a vida e para os meus Amigos, por sempre me terem incentivado a continuar. Para a minha avó materna. A todos, muito Obrigado. iv v Dedicado à Luísa. vi Development of oral tablets containing Nicorandil vii Abstract The development of any drug product is always guided by the goal of designing a product which complies with defined specifications at release and that is able to maintain its physic-chemical properties and stability within acceptable limits during its shelf-life. Therefore, the compliance with the principles of Quality, Safety and Efficacy depends on a meticulous and planned pharmaceutical development work. The present work focused on the formulation of a stable Nicorandil oral tablet dosage form, through a careful evaluation and choice of the Drug Substance, the excipients and selection of an optimized manufacturing process. Critical factors affecting Nicorandil stability were discussed and evaluated under a risk management strategy considering their importance to the stability of the drug product. Selection of excipients was done through a DS/excipients compatibility studies and single and total impurities were quantified by HPLC analytical technique, to select those who showed better chemical stability. Development of the formulation aimed to produce 10mg Nicorandil tablets, by direct compression of a homogeneous powder mixture and was conducted along four trials. Finished product pharmaceutical performance and chemical stability after a three months short term stability study, in ICH conditions, was evaluated and compared with a reference drug product. Statistical evaluation of the multiple parameters suggests that, in this period, there are no significant differences between test and reference, either in pharmaceutical performance or chemical stability. Key words: Nicorandil, pharmaceutical development, oral tablets, stability. viii Development of oral tablets containing Nicorandil ix Resumo O desenvolvimento de qualquer medicamento deve ser orientado para a obtenção de um produto que cumpra com as especificações definidas à data do fabrico e que mantenha as suas propriedades físico-químicas e de estabilidade dentro de limites aceitáveis durante o seu ciclo de vida. Por isso o cumprimento dos princípios de Qualidade, Segurança e Eficácia depende de um meticuloso planeamento do desenvolvimento farmacêutico. O trabalho apresentado teve como objetivo o desenvolvimento de uma formulação estável de comprimidos de Nicorandil, através de uma criteriosa caraterização da substância ativa, de uma escolha fundamentada de excipientes e de um processo otimizado de fabrico. Os fatores críticos que afetam a estabilidade do Nicorandil foram discutidos e avaliados no âmbito de uma análise de risco, considerando a sua relevância para a estabilidade do produto acabado. A seleção de excipientes foi feita recorrendo a estudos de compatibilidade destes com a substância ativa, usando a quantificação das impurezas individuais e totais recorrendo à técnica analítica de HPLC, para selecionar os que indiciavam melhor compatibilidade. O desenvolvimento da formulação teve como objetivo a produção de comprimidos contendo 10mg de Nicorandil, por compressão direta de uma mistura de pós homogénea e é constituído por 4 etapas. A avaliação dos comprimidos incidiu sobre o desempenho farmacêutico e sobre a estabilidade química após um estudo de estabilidade abreviado de 3 meses em condições ICH. Os resultados desta avaliação foram comparados com um produto de referência. A avaliação estatística dos dados gerados sugere que, neste período de tempo, não existem diferenças significativas entre o produto teste e o de referência, quer a nível de desempenho farmacêutico, quer a nível da estabilidade. Key words: Nicorandil, desenvolvimento farmacêutico, comprimidos orais, estabilidade. Development of oral tablets containing Nicorandil xvi Table 35. Trial #1. Quantitative composition of test mixtures ................................. 86 Table 36. Trial #1. Compression tests results ........................................................ 87 Table 37. Trial #1. Tablet characterization results .................................................. 89 Table 38. Trial #2. Quantitative composition of test mixtures ................................. 92 Table 39. Trial #2. Mixture flowability and mixture characterization results ............ 93 Table 40. Trial #2. Blend homogeneity ................................................................... 93 Table 41. Trial #2. 10mg tablets characterization results ....................................... 94 Table 42. Trial #3. Qualitative composition ............................................................ 96 Table 43. Trial #3. Process summary table ............................................................ 97 Table 44. Trial #3. Mixture characterization results .............................................. 100 Table 45. Trial #3. Mixture homogeneity results ................................................... 102 Table 46. Trial #3. Tablets characterization results .............................................. 102 Table 47. Manufacturing parameters to be tested on trial #4 ................................ 103 Table 48. Trial #4. Quantitative composition ........................................................ 104 Table 49. Trial #4. Mixture homogeneity results ................................................... 106 Table 50. Trial #4. Tablets characterisation results .............................................. 107 Table 51. Trial #4. Uniformity of dosage unit ........................................................ 108 Table 52. Final risk assessment on DS attributes ................................................ 110 Table 53. Final risk assessment on excipients attributes ...................................... 111 Table 54. Final risk assessment on manufacturing process ................................. 112 Table 55. 10min dissolution Tukey HSD results ................................................... 115 Table 56. 15min dissolution Tukey HSD results ................................................... 116 Table 57. 30min dissolution Tukey HSD results ................................................... 117 Table 58. Tests performed during stability study .................................................. 118 Table 59. Summary of stability results of test formulation (30N) ........................... 119 Table 60. Summary of stability results of test formulation (60N) ........................... 120 Table 61. TPP of test product conclusion ............................................................. 129 Development of oral tablets containing Nicorandil xvii Acronyms API - Active pharmaceutical ingredient aw - Water activity cGMP - Current Good Manufacturing Practices CPP - Critical Process Parameter CQA - Critical Quality Attributes CU - Content Uniformity DS Drug Substance FDA - Food and Drug Administration FTIR - Fourier Transformate Infra Red GIT - Gastrointestinal tract ICH - International Conference on Harmonization KF Karl Fischer (total water determination) N Newton NA - Not applicable ND - Not detected NIR - Near-infrared NMT Not more than Ph. Eur. - European Pharmacopoeia QTPP - Quality Target Product Profile RH - Relative humidity RSD Relative Standard Deviation SSG - Sodium starch glycolate Tg - Glass transition temperature TPP - Target Product Profile udl - Under detection limit USP - United States Pharmacopeia Water (u.p.) - Ultra pure water XRPD - X-ray powder diffraction Development of oral tablets containing Nicorandil xviii Development of oral tablets containing Nicorandil 1 Introduction Development of oral tablets containing Nicorandil 2 Development of oral tablets containing Nicorandil Introduction 3 1. Theory and review of the literature Solid oral dosage forms and especially tablets for oral administration, are the most common pharmaceutical dosage form (1). Virtually ubiquitous, oral tablets, despite its apparent simplicity, demand a careful research and development process until being launched into market. Tablets, as well as any drug product, go through a design process until it assumes its final shape. This design process is called pharmaceutical development. The purpose of the pharmaceutical development is to demonstrate, through the compilation of scientific evidences, that the achievement of a specific formulation of the dosage form, composed by the drug substance (DS) and specific excipients and its manufacturing processes, robust and suitable for the intended use (2). The information and knowledge gained from pharmaceutical development studies include a variable number of test formulations with different compositions and manufacturing process trials using different process parameters. All of this data provide scientific knowledge to support the establishment of the design space, specifications, and manufacturing controls. Concerning the pharmaceutical development, two major sequential stages have an important role in drug development: pre-formulation, where the DS is studied and tested and the formulation, where the dosage forms is defined. 1.1. Pre-formulation and formulation The development of any drug product requires an extensive chemical and physical characterization of the DS and excipients, which is the basis to set a proper strategy for the development process (3). The purpose of pre-formulation and formulation is to gather knowledge on the DS, excipients, manufacturing process and finished drug product to demonstrate the desired pharmaceutical performance, has predictable therapeutic response and stability of the final drug product throughout its life cycle. In other words, it means it has to demonstrate the necessary quality, safety and efficacy properties and still be able to be manufactured at an industrial scale. Pre-formulation is the first stage where the DS properties are investigated and where those which can have an impact on the formulation design are identified and studied, such as: crystallinity, solubility, chemical and physical stability and polymorphism (4). In this stage it is also necessary to evaluate and select adequate excipients to ensure an optimal performance of the drug product. Although, selecting excipients is not a straightforward process, since it must be demonstrated that they are chemical and Development of oral tablets containing Nicorandil Introduction 4 physically compatible with the DS. This issue is of utmost importance since it is directly related to the stability and quality of the final drug product (5, 6). 1.2. Stability of drug products DS and drug product stability is an issue of major importance since it is a wellrecognized cause of poor drug product quality, safety and efficacy (7-9). A drug product can only remain in market while its quality profile comply with pharmacopoeial standards and manufacturer specifications, which have been previously approved by regulatory agencies. These specifications allow the establishment of the shelf-life period (10). Stability of drug products is directly related to patient safety. It is mandatory to present enough evidences of drug product stability to regulatory authorities to achieve market authorization. On the other hand, stability of the drug product is also related to economic success. Ultimately, instability of DS and drug products will cause many adverse reactions on patients due to the presence of degradation products and/or low efficacy, due to loss of potency. From the regulatory point of view, patient safety is the reason why DS and drug product stability are highly regulated through international standards and guidelines which helps to guarantee the necessary quality standards of the DS and drug product prior to market entry. By last, if a drug product with stability issues enters market it will most likely be subject to product recalls, bad publicity, low expiry date and high costs, either direct or indirect, to pharmaceutical companies. Eventually, every single drug product will chemically and physically change along its lifecycle, since chemical and physical interactions are unavoidable. Therefore, developing a drug product must take into consideration strategies to guarantee product stability and compliance with specifications as long as possible. A drug product is a complex system formed by molecules of DS and excipients. These molecules have specific structures and organic groups that will dictate the physical and chemical properties of the raw materials that they originate but also the properties of the finished drug product. These interactions are also influenced by external factors such as temperature, humidity, light or oxygen, manufacturing process, packaging material and transport and storage conditions. The main consequence associated with drug product stability is the increased level of toxicity that degradation products bring to the patients and therefore pharmaceutical Development of oral tablets containing Nicorandil Introduction 5 companies are bound to perform and report stability studies on their drug products (8, 9, 11). These stability studies are performed initially during the pharmaceutical development stage but also along the product life time, while it remains on market. The initial stabilities studies will serve to propose an expiry date, or in other words to define the time during which the drug product complies with its critical quality attributes and is within the defined specifications. On the other hand, follow up stability studies and long term studies will serve to monitor and support the previously defined expire date. When addressing the stability of drug products it is necessary to specify that this can be chemical, physical and microbiological stability (9). Chemical stability is of major importance and can be evaluated and quantified through analytical procedures using different techniques. Identity, assay and impurity levels are mandatory parameters to be evaluated, since these parameters are the ones that can change under several factors, as already mentioned, but also due to interactions between DS (if more than one are present in the drug product) and between DS and excipients. Many chemical reactions are promoted due to catalysts substances present in the excipients, water molecules or micro-environmental pH. These chemical reactions can cause DS degradation, through mechanisms such as hydrolysis, oxidation, reduction, decarboxylation, ring cleavage, polymerization, polymorphic changes and photolysis, only to mention a few common examples (9). All of these potential degradation pathways lead to the appearance of degradation products related to a potential increase in product toxicity. This is why it is also necessary to achieve an adequate knowledge of the degradation process and to identify the degradation products formed (11). Other factors that influence the chemical stability are, for example, temperature, light, oxygen and excipients present on the formulation of the drug product, among others. Mechanical strengths like pressure/compaction forces, milling and grinding may also affect chemical as well as physical stability of the DS and drug products (9). Physical stability is related to the physical properties of the DS and excipients or alterations on these along drug product shelf life. Physical stability is related to drug product properties that affect its efficacy, such as solubility, dissolution, disintegration, resistance to crushing, friability, water content, polymorphic changes and crystalline/amorphous transitions (7, 12). Bioavailability is, therefore, dependent on this type of stability, since these properties are related to the in vivo performance of the drug product. Microbiological stability, although less critical in solid oral dosage forms than in other pharmaceutical forms, such as liquids or semi solids, must be monitored along the long Development of oral tablets containing Nicorandil Introduction 6 term stability study to ensure that proper limits, defined by compendial specifications, are respected. International guidelines are the standard information source to properly conduct a stability study which is essential to demonstrate that a product remains within allowed impurity levels. It is generally accepted by regulatory agencies a decrease up to 95% of the labelled DS amount during shelf life of a drug product, although, shelf life is mainly dictated by the level of degradation products (13). The International Conference on Harmonization, through its impurity guidelines (10, 14), specifies the reporting, identification, and qualification thresholds for impurities in drug products. A limit between 0.1% - 1% of total and single degradation products is usually the interval in which the identification or qualification is mandatory (13). The stability assessment of drug products can be done using several strategies. Since it is not practical to perform an on-going (or long term) stability evaluation during product development, it became necessary to speed up testing times through accelerated stability studies in standardized conditions. These studies are often carried out both on the DS and drug products at temperatures from 25ºC up to 40°C, under relative humidity conditions from 60% to 75% (15, 16) and during a defined period of time. These type of studies are also known as isothermal stress testing (IST) (17). ICH long term, intermediate and accelerated conditions for these studies are defined in international guidelines and are 25ºC/60%RH, 30ºC/65%RH and 40ºC/75%RH (16). Although the prediction of shelf life can be based on studies under accelerated conditions, data at the recommended storage temperature are generally required to support the actual shelf life of marketed products and to confirm the results of the accelerated stability process (16), however, the use of statistics applied to the real time data should allow extension of shelf-life (18). A simple extrapolation can be done to predict shelf-life by considering that the shelf life determined at 40°C/75%RH is about one-fourth of that at room temperature. 1.2.1. Solid state stability Solid state reactions are more complex and take longer than reactions which take place in solution state because in the solid state there are less number of molecular contacts between drug and excipient molecules and there are also multiple phase reactions which makes reactions in the solid state more difficult to interpret (19). These type of reactions can also be studied through the increase of temperature and humidity. Higher values of these two factors accelerate the speed at which degradation reactions take place, which on its turn increase the amount of degradation Development of oral tablets containing Nicorandil Introduction 7 products. Such strategy allows the quantification of these products on shorter time, which otherwise would take unpractical time to appear. The purpose of these studies is to have an indication of stability through data extrapolation, assuming that the degradation mechanism at higher temperatures and relative humidity levels is the same as that at 25°C. 1.2.2. Temperature Isothermal stress testing or degradation of samples at constant higher temperatures is kind of stress condition commonly used for compatibility studies (13, 20). It is based on the assumption that the kinetics of degradation reactions follows Arrhenius kinetics, which states the reaction rate dependence on temperature (13). However, this need not to be the case and a non-linear Arrhenius plot may be an indication of change of degradation mechanism as the temperature is increased. Extrapolation of shelf life is based on the assumption that a solid-state reaction follows Arrhenius kinetics and that an activation energy determined at higher temperatures can be used to calculate the rate and shelf life at room temperature. The assumption is valid if the reaction at higher temperatures also occurs at room temperature and follows the same degradation pathway and no irrelevant degradation products are formed meanwhile (18). A shift in the primary degradation processes is often indicated by the appearance of additional impurity peaks in the HPLC analysis or changes in the retention factor (Rf) values that are an indication of interaction or decomposition. Some authors state that if no interaction is observed at 50 to 60ºC, especially in the presence of moisture and air, none can be expected at lower temperatures (21). Therefore, usually more than one stressed condition is chosen to determine if the degradation reactions observed at elevated temperatures might be the ones which have such high activation energies that they occur only under pharmaceutically irrelevant conditions. 1.2.3. Water Content and Hygroscopicity Moisture present in dosage forms may come from several sources: bulk active pharmaceutical ingredient (API), excipients, manufacturing processes and environmental conditions (9). The mechanisms of water interaction in solid state are related to the water molecule characteristics. Water is a molecule with particular characteristics thanks to the hydrogen bonds it can form with other molecules. Hydrogen bond is a type of electrostatic force that rules water properties in its physical states and also its interactions with solids. Development of oral tablets containing Nicorandil Introduction 14 Table 1. Risk ranking system Low Broadly acceptable risk. No further investigation is needed. Medium Risk is acceptable. Further investigation may be needed to reduce the risk. High Risk is unacceptable. Further investigation is needed to reduce the risk. The risk assessment tool links material attributes and critical process parameters (CPP) to drug product Critical Quality Attributes (CQA’s) to correlate and evaluate the potential impact that each parameter will have on them. CQA’s are physical, chemical, biological or microbiological properties that should be within an appropriate limit, range or distribution, to ensure the desired product quality. CQAs are generally associated with the drug substance, excipients, intermediates (in-process materials) and drug product (2). Additionally, (CPP) are process parameter whose variability has an impact on a critical quality attribute and therefore should be monitored or controlled to ensure the process produces the desired quality. Risk assessment is typically performed early in the pharmaceutical development process and is updated during development when materials, process and product knowledge is obtained. Despite being a useful tool that helps to support scientifically strong product dossiers to regulatory authorities it is not always appropriate or necessary to use a formal risk management process. The use of informal risk management processes (using empirical tools and/or internal procedures) can also be considered acceptable. Prior to the start of the development process it was necessary to define the target profile so that a risk assessment and risk management strategies could be defined (31). Generally, a Target Product Profile (TPP), defines the product attributes and it is often expressed primarily in clinical terms, but should also include the pharmaceutical, technical, regulatory and commercial/marketing attributes required of the product. The TPP is based on the ideal product characteristics, which are considered to be desirable. For the product development process the Quality Target Product Profile (30) (QTPP) was selected based on the reference product characteristics, as it relates to the quality, safety and efficacy, as well as on the DS characteristics. QTPP is a prospective summary of the quality characteristics of a drug product that ideally will be achieved to ensure the desired quality, taking into account safety and efficacy of the drug product. For the purpose of this work, the potential critical quality attributes (CQAs) were evaluated considering the DS, excipients and drug product characteristics that can have an impact on drug product quality. Once identified it was possible to evaluated and control these characteristics. Development of oral tablets containing Nicorandil Introduction 15 Additionally, product and process design should be stated as early as possible, while identifying critical parameters and process monitoring and control helps to correctly guide product development. The selection of an adequate manufacturing process was based on all the information gathered and supported by a risk assessment used during all stages of the development to identify potential high risk formulation and process parameters so that a control strategy could be implemented. Based on the development layout a range of formulation and process variables were defined as robustness limits inside which variations are accepted without compromising quality safety and efficacy of the drug product. These CQA are considered priorities in the risk assessment evaluation. For this product, assay, degradation products, dissolution, content uniformity (CU), water content and hardness of tablets are identified as CQA’s that have the potential to be impacted by the formulation and/or process variables can influence product stability. Quality attributes that are not considered critical, such as tablets physical attributes, will be evaluated according to compendial standards and reference product characteristics. 4. Nicorandil 4.1. Background Nicorandil is a DS produced for the first time in 1984 by Chugai Pharmaceutical Co®. Ltd. Japan (32), company that still owns the marketing rights for Nicorandil. Chugai Pharmaceutical has licensed its production to companies such as Merck® and SanofiAventis® under the names of Dancor®, Ikorel® and Sigmart®, among other brand names. Nicorandil market sales represent several millions of euros in the last 5 to 10 years in Japan and across 11 countries throughout Asia and Europe. Nicorandil became a widely used anti-angina therapeutic agent since its launch in Japan in 1984 and in Europe in 1994. Ever since and after years of clinical experience worldwide, the safety record of Nicorandil continues to give physicians a reliable source of solutions to treat this major patient group (33) increasing the importance of this DS in the treatment of cardiovascular diseases due to the minimum effects on the dynamics of cardiovascular circulation and on cardiac functions (34). When administered twice-daily the dosage of Nicorandil ensures 24 hours control (35) and provides an effective and tolerable therapy for patients with angina, either as monotherapy in up to 80% of patients (36) but also in combination with other anti-angina therapies, without interactions or an increase in adverse reactions (37). Development of oral tablets containing Nicorandil Introduction 16 Nicorandil is a nitrate derivative of nicotinamide (nicotinamide ester) that has a dual mechanism of pharmacological action (38) and belongs to a group of medicines called vasodilators. Nicorandil widens the coronary blood vessels to increase the blood supply to the heart hence relieving angina effects. This effect is caused by its nitrate group which promotes venous relaxation through stimulation of guanylate cyclase (39). Another effect of Nicorandil is the widening of systemic blood vessels. This means that the total pumping effort of the heart is reduced (40). This effect is done through the opening of potassium channels caused by the nicotinamide ring (41). The combined action improves coronary blood flow to post-stenotic regions, reduces preload and after load and improves the oxygen balance in the myocardium. This characteristically pharmacological action makes Nicorandil suitable for the prevention and long term treatment of chronic stable angina pectoris and reduction of the risk of acute coronary syndromes in patients with chronic stable angina. The common initial oral dose is 10mg twice daily, increased as necessary to a maximum of 30mg twice daily. Bioavailability is about 75% to 80%. Nicorandil is rapidly and well absorbed from the gastro intestinal tract but food can decrease the rate of absorption. First-pass metabolism is not significant and Nicorandil molecule is only slightly bound to plasma proteins. Maximum plasma concentrations are achieved in 30 to 60 minutes after intake and are directly related to the dosage intake. Metabolism occurs mainly by de-nitration of the molecule through its side chain. A second degradation mechanism occurs through production of N-(2-hydroxyethyl)-nicotinamide eventually forming nicotinic acid. Further metabolisation of these products leads to the formation of water and vitamin B complex substances. Less than 20% of an administered dose is excreted in the urine as metabolites. Less than 2% of the dose is excreted via the biliary route and 10% of the dose can be found in plasma but is rapidly eliminated. The main phase of elimination has a half-life of about 1 hour. 4.2. Reaction and Degradation Mechanisms Nicorandil molecule represents a challenge for the formulation scientist due to its properties which are dictated by its tridimensional molecular structure (42), crystalline lattice and composition in organic groups, which turns it in a stable molecule when unprocessed (43) but highly unstable once it is processed and included in a drug product formulation (44, 45). Development of oral tablets containing Nicorandil Introduction 17 Nicorandil molecule, as highlighted on Figure 1, has four organic groups: a pyridine ring (#1), an amide group (#2), a secondary amine group (#3) and a nitrate group (#4). Figure 1. Nicorandil organic groups The molecular structure of Nicorandil does not present chiral carbon atoms or isomerism and according to current knowledge it has no known polymorphs. Nicorandil molecule adopts a folded conformation, which is stabilized by intramolecular Van der Walls contacts between the carbonyl group oxygen atom and the nitrogen atom in the nitro group. Intermolecular hydrogen bonds and short contacts are observed (42). Besides the molecular folded conformation, Nicorandil is arranged in a crystalline pattern so that the Nitrogen atoms of the pyridine rings are close together with the atoms of C-CH2ONO2 neighboring group, at a distance 0.3367 nm, less than the sum of the van der Waals radii of C and N (0.3484 nm) (42). Plot atoms approaching Nitrogen and Carbon atoms can be regarded as the reaction center. This molecular structure and conformation, as illustrated in Figure 2 (adapted from reference 32), determines its major degradation pathway and the presence of substituents strongly influences its reactivity. Figure 2. Crystalline packing view of Nicorandil Development of oral tablets containing Nicorandil Introduction 18 Nicorandil, as a nitrate ester, mainly decomposes through a hydrolysis reaction which starts in the nitro ester bond (46). Besides this, the electron withdrawing functional group close to the ester bond which makes it a candidate for nucleophilic attack by hydroxide ions. This explains its strong degradation in presence of water or high relative humidity environments. Since amide bonds (also present in Nicorandil molecule) are less susceptible to hydrolysis than ester bonds (because the carbonyl carbon of the amide bond is less electrophilic due to the double bond of the Carbon-Nitrogen) and the leaving group, (an amine) is a poor leaving group, the first cleavage, occurs in the ester bond, releasing this way, the nitrate ion. These degradation reactions in aqueous solution follows a first order kinetic reaction either in alkaline or acid environment although it is faster in alkaline pH originating an intermediate product with an UV absorption spectra near 335nm (47). There are several known degradation products identified (Figure 3). Figure 3. Nicorandil main degradation products Development of oral tablets containing Nicorandil Introduction 19 The hydrolysis reaction of Nicorandil starts by the formation of an intermediate molecule (3-(4,5-dihydro-2-oxazolyl) pyridine)) (48) (Figure 4). Figure 4. Hydrolysis reaction of Nicorandil This reaction has been further elucidated (47) and explains the formation of the Nitrate ion (Figure 5). Figure 5. Hydrolysis of Nicorandil and Nitrate formation Along with the formation of the intermediate molecule (II), the nitrate ion is also formed. This reaction evolves into the formation of one of the major degradation products, N-(2-hydroxyethyl) nicotinamide, when the intermediate compound reacts with water (Figure 6). Figure 6. Intermediate compound formation Development of oral tablets containing Nicorandil Introduction 20 From this intermediate compound (III) nicotinic acid (V) and N-(2-hydroxyethyl) nicotinamide (IV) are formed, depending on conditions (47) (Figure 7). Figure 7. Degradation reactions sequence from intermediate compound Besides these known degradation impurities, Nicorandil has been described in a research paper as a molecule that participates in solid state quaternization polymerization reactions (49). The proposed structure for the dimer formed through this reaction is shown on Figure 8. Figure 8. Nicorandil dimer Further polymerization is possible through the additional bonds between Nicorandil molecules, forming additional degradation products. Nicorandil molecules can form dimers, trimers and tetramers, which have been described as degradation products in British Pharmacopoeia (2014) Nicorandil tablets monograph (revised). The polymerization reaction forms polymeric compounds between 40ºC and 70ºC which are soluble in water and insoluble in organic solvents. The general polymerization reaction is shown on Figure 9 (adapted from reference 34). Figure 9. Nicorandil polymerization reaction Development of oral tablets containing Nicorandil Introduction 21 It has been described that this degradation is not as strong in acidic environments as it is in alkaline environments (41, 43, 46, 50), probably due to the low pKa of Nicorandil. Another factor that is associated with increased degradation is the damage induced on the crystal lattice of Nicorandil. Such damage can be induced by common operations associated with the manufacture of solid dosage forms such as milling, grinding or tableting. The disruption of the crystalline conformation is linked with a change in the free energy at the surface of the crystalline structure (surface energy) which means that more energy is available to participate or initiate degradation reactions (9, 51, 52). 4.3. Critical Drug Substance attributes Considering the previous information and bibliographic search, DS attributes were selected and discussed regarding their critic level (Table 2). Table 2. Critical Drug Substance attributes assessement DS attributes Justification Is it a CQA? Particle size distribution Particle size distribution is a critical attribute since it can negatively influence blend homogeneity, solubility, dissolution and content uniformity of tablets. Yes Hygroscopicity Hygroscopicity is a property related to product stability since Nicorandil is sensitive to high moisture levels. Hygroscopic materials adsorb moisture from the environment into the formulation increasing the water molecules amounts available for reaction. Since Nicorandil is not hygroscopic this parameter is not considered a CQA. No Solubility Nicorandil is referred in manufacturer’s CoA as sparingly soluble. Solubility is a critical attribute since it can negatively affect dissolution and assay, therefore this parameter must be evaluated. Yes Water content Water content is a critical attribute since high levels of water on the components and drug product might induce higher degradation rates. Since Nicorandil presents low water content this parameter is not a CQA. No Chemical stability Nicorandil is an unstable molecule when processed and blended with other substances. Formulation development must be designed considering the factors that can promote degradation of Nicorandil. Yes Flowability Flow properties of the components of a formulation obtained by direct compression are always critical attributes and require further testing. Yes Polymorphism Nicorandil has no known polymorphs, therefore this parameter is not considered critical. No Development of oral tablets containing Nicorandil Introduction 22 5. Reference Product The reference drug product (RP) marketed is an uncoated, white, round, with faceted edges, weighing approximately 100mg and 200mg oral tablet with a label indication of 10mg and 20mg of Nicorandi, respectively. According to the public literature (53) the qualitative and quantitative formulation of the RP is described in Table 3. Table 3. Qualitative and quantitative composition of Reference Product Qualitative formulation Quantitative formulation Nicorandil 10% Mannitol 76% Corn starch 1% Croscarmellose sodium 5% Stearic acid 8% Nicorandil RP has a shelf life of 18 months when stored in a dry place below 25ºC and each blister strip should be used within 30 days of opening. Primary packaging is composed of hard tempered aluminium foil/ (Polyamide/aluminium/PVC) blister strips containing 10 tablets. Each tablet inside the blister is linked to a round disk with a desiccant agent (silica gel) placed on one side of the blister, as can be seen on Figure 10. Figure 10. Primary packaging material of Nicorandil 10mg reference product This type of design allows the control of moisture inside each blister pocket although once one tablet is removed all other will be exposed to air due to the communication channels linking each pocket. A detailed physical and chemical characterization of the RP is described in the pre-formulation section. Development of oral tablets containing Nicorandil Introduction 23 6. Patent landscape The pharmaceutical industry is prolific in generating intellectual property. The protection of such intellectual property is done through patents. A patent is an exclusive right granted for an invention (intellectual property) and lasts generally for a period of twenty years. Patents are territorial rights and only applicable in the country or groups of countries in which a patent has been filled or granted in accordance with the law of that country or according to the patent treaty established between groups of countries (54). Patents can be issued, for example, over DS, drug products or manufacturing processes. Patents are a valuable source of information not only to avoid infringement of third parties intellectual property but also because it describes previous work which is helpful to guide alternative, novelty approaches to formulate a drug product. With the purpose to collect support information to the present work on Nicorandil formulations and stability, a patent search was conducted and the selected documents studied are described on Table 4. Table 4. List of patents selected for evaluation Office Number Title Date USPTO 4,200,640 Nitric Esther of N-(2-hydroxyethyl) Nicotinamide and Pharmaceutical Use. 29 Apr 1980 USPTO 4,803,213 Method For Production of Stable Nicorandil Preparation. 07 Feb 1989 USPTO 4,822,808 Method For Production of Stable Nicorandil Preparation. 18 Apr 1989 EPO 0 574 221 B1 Pharmaceutical Stable Formulations of Nicorandil. 15 Dec 1993 EPO 1 001 773 B1 Oral Solid Pharmaceutical Compositions Containing Nicorandil For a Modulated Release and the Process for their Preparation. 06 Feb 2002 Nicorandil synthesis is disclosed in patent USPTO 4,200,640. Additionally, this patent also proposes a few formulations for solid oral dosage forms containing Nicorandil to support that this compound can be formulated into different pharmaceutical formulations. Some examples of Nicorandil formulations proposed are described on Table 5. Development of oral tablets containing Nicorandil Aims of the Study 30 Table 6. Target Product Profile proposal for the finished product (cont.) Parameter Target proposal Justification Is it a CQA? Tablet shape Round, biconvex Size and shape are not critical attributes. Tablets dimensions chosen are similar to the RP. No Tablet dimensions 7 mm Score and embossing None Score and embossing are not critical attributes. Tablet divisibility is possible in the 10mg strength although such purpose falls outside the scope of this work. No Colour and appearance White Color and appearance are not critical attributes although they are a long term stability indicator of physical incompatibilities and should be evaluated. No Weight 100mg Tablet weight can affect safety and efficacy since it is related to the uniformity of dosage unit. Weight is similar to the 10mg strenght tablet of the RP. Since it is a compendial routine test for tablets it is not considered a critical attribute for the scope of this work but must be neverthless evaluated. No Friability NMT 1.0% w/w Compendial routine test for tablets. Since tablet hardness is a critical quality attribute, friability must be monitored to avoid loss of structural integrity of tablets during handling and transport. Requires close monitoring. No Disintegration Tablets should disintegrate in more than 20s and less than 10 minutes Compendial routine test for tablets. Disintegration time has an impact on dissolution profile and hence on efficacy and bioequivalence of the drug product. Requires close monitoring. No Development of oral tablets containing Nicorandil 31 Materials and Methods Development of oral tablets containing Nicorandil 32 Development of oral tablets containing Nicorandil Materials and Methods 33 1. Materials 1.1. Reagents All reagents used were of Analytical Purpose (AP) grade or HPLC grade. The method of preparation is the following: Mobile phase A for HPLC analysis: prepared with Water (u.p.):THF:TEA:TFA (989:3:5:3, v/v). Also used as a solvent for the preparation of samples for HPLC analysis. Mobile phase B for HPLC analysis: prepared with Water (u.p.):THF:TEA:TFA (979:8:5:8, v/v). THF: tetrahydrofuran; TEA: triethylamine; TFA: trifluoroacetic acid. (all from Merck®) HCl 0,1N: Served as dissolution media and was prepared by diluting 8.28mℓ of fuming HCL 37% per 1 liter of water R1. Confirmation of pH was done using a calibrated pH meter. 0.05 M Phosphate buffer solution pH 4.5: Used as buffer solution in dissolution media and solubility testing. Prepared according to Ph. Eur. 4.4.3 by dissolving 6.80g of potassium dihydrogen phosphate R (Merck®) in 1000.0 mℓ of water R. The pH of the solution is 4.5. Phosphate buffer solution pH 7.0 R1: Used as buffer solution in dissolution media and solubility testing. Prepared according to Ph. Eur. 4.4.3 by mixing 250mℓ of 0.2M potassium dihydrogen phosphate R (Merck®) and 148.2 mℓ of an 8 g/l solution of sodium hydroxide R (Merck®). Adjust the pH if necessary. Dilute to 1000 mℓ with water R. 1.2. Excipients Excipients that were used during pre-formulation and formulation studies are listed in Table 7. These are identified by their chemical name, brand names and supplier. 1 Water R. See Ph. Eur. for definition and specification. Development of oral tablets containing Nicorandil Materials and Methods 34 Table 7. List of excipients used during development Non-proprietary name Brand name and grade Supplier Isomalt GalenIQ® 721 Beneo Palatinit® Pregelatinized Starch Starch 1500® LM Colorcon® Sodium starch glycolate Vivastar® PSF JRS Pharma® Sodium alginate Keltone® FMC Biopolymer ® Stearic acid Dub Microlub® 50 Stearinerie Dubois® Microcristalline cellulose Avicel® PH102 FMC Biopolymer ® Anhydrous Colloidal Silicon dioxide Aerosil® / Syloid® AL1-FP Evonik ® / Grace® Mannitol, fine powder Pearlitol C25® Roquette Pharma® Mannitol, coarse grade Pearlitol SD 200® Roquette Pharma® Croscarmellose sodium AcDiSol® FMC Biopolymer ® Crospovidone Kollidon CL® BASF® Sample preparation for compatibility studies Binary and composite mixtures of Nicorandil with excipients were prepared by weighing separately each component into 5mℓ glass vials or petri dishes where they were mixed together with rotation movements and the use of a spatula. Components were added in a 1:1 proportion. With the purpose of evaluating the effect of compression on the compatibility with excipients, Nicorandil was compressed with each excipient in a hydraulic press with 0,5 ton force and 5 ton force during 30s or 5min. Compacts were pulverized using mortar and pestle and the resulting powder was prepared according to the method described in the sample preparation for HPLC. Samples were prepared once and replicates were taken from the source mixture and analyzed. Pre-formulation and Formulation development studies In Table 8 a list of the equipment used can be found. All equipment used were calibrated by a certified entity. Analytical scales were verified regarding response in the working range before each use. All equipment responses were considered adequate at the time of usage. Development of oral tablets containing Nicorandil Materials and Methods 35 Table 8. Equipment used Equipment Manufacturer pH meter inoLab pH Level 2P WTW Analytical balances (range: 0 – 210g; sensitivity: 0,01mg) Mettler Toledo XS205 Module AR402 motor drive adapted with a universal gear and double cone mixer Erweka® Purelab Ultra Elga (ultra pure water source) Enkrott® Heating/ Drying oven Memmert® Vacuum heating oven Heraeus® Instruments Vacutherm Pellet press and dies for FTIR Specadie System Specac® Climate chambers (25ºC/60%; 30ºC/65%; 40ºC/75%) Fitoclima® D1200 Pharma Votsch® HPLC systems VWR Hitachi Elite Lachrom and Shimadzu LC2010C systems with column oven (set up at 25ºC) and photodiode array detector 2. Methods Pre-formulation and formulation studies must be necessarily supported by analytical methods to evaluate the performance and characteristics of the test products along the way. Analytical methods must be developed and validated to demonstrate that such methods are adequate for its purpose and that the results obtained are reliable and reproducible on the working range defined. Method validation are mandatory according to cGMP and extensively documented through international guidelines (55, 56). Several parameters are commonly determined during analytical method development and validation: selectivity/specificity, linearity in the working range, precision (repeatability, intermediate precision and reproducibility), accuracy, stability of solutions, definition of the detection and quantification limits. The present work used dissolution, UV and HPLC methods developed and validated in-house according to international guidelines (ICH) and the acceptance criteria used to evaluate method validation can be consulted in the Annex section. Calculation formulas used in the quantification are described in the Annex section. Whenever Ph. Eur. is referred as compendial source, version 7.0 is to be considered. Development of oral tablets containing Nicorandil Materials and Methods 36 2.1. Statistical analysis Statistical analysis was done using IBM Corp. SPSS Statistics version 22.0. Dissolution tests were compared by one-way ANOVA and Tukey HSD post-hoc tests. For each sample group, a normality test was determined using the Shapiro-Wilk statistic and to determine the homogeneity of variance a Levene’s test was used. A value of p<0.05 was considered significant for all tests. Stability assessment was done by evaluating multiple variables associated with the chemical and physical stability of the dosage form. The chosen statistical tool for this type of data analysis was the cluster analysis (57). A Two Step clustering technique based on the between groups linkage clustering method was used (58). Criterion for the clustering was the Schwarz’s Bayesian Criterion (BIC) and the number of clusters was determined automatically. Measurement between data intervals was done using the squared Euclidean distance. Samples were automatically standardized by the software (Figure 11). Figure 11. Clustering evaluation parameters 2.2. Solubility Solubility, in pharmaceutical terms, is the maximum amount of a DS that can be dissolved in a solvent in a given condition (59). The solubility of a DS is one of the most important properties that needs to be assessed early in the development process. The bioavailability of an orally administered drug depends primarily on its solubility in the gastrointestinal tract and its permeability across cell membranes. This forms the basis of the biopharmaceutical classification system (BCS) (60, 61) which can be used to establish in vitro / in vivo correlations between drug products. The solubility determination also supports analytical method development since a DS needs to be in the solution state to be quantifiable and provides information on the formulation development if there is the need use manufacturing processes or excipients that can improve solubility. Solubility of Nicorandil in purified water was determined according to the Ph. Eur. Section 5.11. – Characters section in monographs. Solubility test is done in several Development of oral tablets containing Nicorandil Materials and Methods 37 sequential steps. The first step consists in weighing 100mg of the Nicorandil in a stoppered tube adding 0.1mℓ of the solvent. This solution is then shake vigorously for 1min and placed in a constant temperature at 25.0 ± 0.5ºC for 15min. If the DS is completely dissolved it is considered very soluble (S>100mg/0.1mℓ). In the case of the DS is not completely dissolved the dissolution procedure is repeated by adding to the sample more 0.9mℓ (total 1mℓ) more of the solvent. This procedure is repeated in sequence with additional volumes of 10, 30, 100, 1000 and 10000mℓ until all DS is dissolved. According to the total volume added the DS is classified in terms of solubility according to Figure 12. Figure 12. Solubility classification according to Ph. Eur. 2.3. Dissolution Dissolution is the dynamic process by which DS is dissolved in a defined solvent and it is characterized by the rate at which it dissolves versus time. In vitro dissolution testing serves many purposes: it guides the formulation and product development process toward optimization; to assess BA/BE studies; to monitor drug product performance during stability testing or quality control release, for example. One of the requirements to conduct an appropriate dissolution test is to use a sufficient volume of dissolution medium, which should be able to dissolve the expected amount of drug released from a drug product. 2.3.1. Sink conditions evaluation According to the Ph. Eur. sink conditions are met for a DS when 3 to 10 times its solubilization volume are above the saturation volume. Nicorandil sink conditions were assessed in three dissolution media covering the relevant physiological pH of the GIT (pH ranging from 1.1 to 7.0) and considering that Nicorandil is a sparingly soluble DS, therefore, a dissolution volume of 900mℓ is preferred. Considering that the highest strength marketed is 20mg, maximum concentration in a 900mℓ dissolution vessel would be 0.0222mg/mℓ. Assuming that five times this Development of oral tablets containing Nicorandil Materials and Methods 38 concentration is enough to demonstrate sink conditions, then if more than 0.111mg/mℓ can be dissolved in the buffer solutions then sink conditions can be demonstrated. Sink conditions testing was done in duplicate by weighing approximately 5.8mg of Nicorandil into a 50mℓ volumetric flask. To demonstrate solubility, samples were analysed in UV spectrophotometry against a standard solution after proper dilution (final concentration: 0.022mg/mℓ). Standard solution was prepared by accurately weighing approximately 22.2mg of Nicorandil into a 200mℓ volumetric flask and diluting 4mℓ of this solution into a 20mℓ volumetric flask (final concentration: 0.022mg/mℓ). The results are presented in Table 9. Table 9. Nicorandil sink conditions assessment Dissolution media tested Calculated solubility (mg/mℓ) Working concentration / max solubility ratio HCl 0.1N 0.1176 (+ 0.03) 18.7% Phosphate buffer pH 4.5 (Ph. Eur.) 0.1152 (+ 0.03) 19.1% Phosphate buffer pH 7.0 (0.025M) (Ph. Eur.) 0.1174 (+ 0.03) 18.7% Results indicate that the working concentration is less than 20% of the calculated solubility in all dissolution media tested which means that sink conditions are met and that Nicorandil can be solubilized at least five times, its highest marketed strength (20mg) in 900mℓ dissolution volume. Under the Biopharmaceutical Classification System (BCS), Nicorandil can be considered as a Class 1 DS since it is highly permeable and highly soluble according to the BCS standards which state that when more than the highest strength is soluble in 250mℓ or less the DS is considered highly soluble. In this case it has been demonstrated that Nicorandil solubility is more than 20mg/250mℓ = 0.08mg/mℓ. 2.3.2. Dissolution conditions The selection of the dissolution medium considered that as an immediate release formulation Nicorandil must be quickly dissolved in the gastric fluids so that it can be promptly ready for absorption. A suitable dissolution media for this purpose is HCl 0.1N. Experimental dissolution was carried out in a calibrated Varian VK 7000 with Cary 50 spectrophotometer complying with Ph. Eur. (2.9.3) specifications (apparatus 2). Initial equipment set up considers 900 mℓ of HCl 0.1 N (pH 1.1 + 0.05) in each of the six dissolution vessels. The temperature of the media was 37.0  0.5ºC. At the start of the test one tablet is weighed and placed in each dissolution vessel under 50 rpm stirring rate. Development of oral tablets containing Nicorandil Materials and Methods 39 Dissolution samples were collected automatically and analyzed by UV spectrophotometry at 262nm wavelength in 1.0cm quartz cells, against a reference standard, at the beginning of the dissolution test (blank measurement) and at 5 minutes interval until 30minutes. Reference standard was prepared by weighing accurately 22.4mg approximately of Nicorandil working standard into a 200mℓ volumetric flask and dissolving with HCl 0.1N. Afterwards 2.0mℓ are diluted in a 20mℓ volumetric flask. Concentration of the final reference solution is 0.011mg/mℓ. 2.4. Ultraviolet spectroscopy UV method is a fast and simple method that can be used in DS quantification and identification. The first step that needs to be taken when choosing UV analysis is to select a suitable wavelength showing an adequate absorbance range, at which Nicorandil can be quantified, this can be done by tracing a spectra of the DS solution along the UV range and evaluating the existing peaks. A standard solution of Nicorandil was prepared at the concentration of 0.022mg/mℓ in three dissolution media/buffers: HCl 0.1N, phosphate buffer pH 4.5 (Ph. Eur.) and 0.025M phosphate buffer pH 7.0 (Ph. Eur.) and analysed in UV using 1cm quartz cells. Nicorandil DS solution presents a maximum absorbance peak around 262nm as can be seen in Figure 13, which is suitable for the quantification of Nicorandil based on UV spectrophotometry. Figure 13. Nicorandil UV spectra in different pH Development of oral tablets containing Nicorandil Materials and Methods 46 Development of oral tablets containing Nicorandil 47 Results and Discussion Development of oral tablets containing Nicorandil 48 Development of oral tablets containing Nicorandil Results and Discussion 49 1. Pre-formulation studies 1.1. DS characterization Two major sources of information regarding chemical and physical parameters and other properties of the DS are the manufacturer’s Certificate of Analysis (CoA) and compendial sources such as the major Pharmacopoeias. The information contained in these references are the first information available on DS and contains important information that can be used as a start point for pre-formulation studies. Nicorandil is the international non-proprietary name for N-[2-(nitroxy)-ethyl]-3pyridinecarboxamide (chemical name) or N-(2-hydroxyethyl)-nicotinamide nitrate ester and is a DS described in the Japanese Pharmacopoeia (69). Its molecular formula is C8H9N3O4 and has a relative molecular weight of 211.18. Nicorandil is a DS that is freely soluble in methanol, ethanol (99.5%) and glacial acetic acid. It is soluble in acetic anhydride, sparingly soluble in water and slightly soluble in ether. It is poorly soluble in ethyl ether or benzene. Nicorandil melts and decomposes between 89° and 94°C and has an absorption coefficient E1% (1cm, max 262 nm, H2O) of 161-175 AU. The pH of 1% aqueous solution is 5.7 - 5.8 and its pKa is 3.18. Nicorandil is a non-hygroscopic substance, stable in the crystalline form when stored at about 5°C (+ 3°C) in a well-closed container (69), although it is not stable at room temperature or in presence of humidity. When in aqueous solution it is highly unstable at room temperature. Nicorandil is a white to off white crystalline powder with a soft consistency. It is possible to observe lumps and aggregates (Figure 14) which can reach approximately 6 to 8cm in their maximum length, although can be easily scattered. There are also hard, small size aggregates, not larger than a couple of millimetres which are difficult to scatter, even using manual or mechanical sieving. Development of oral tablets containing Nicorandil Results and Discussion 50 Figure 14. Bulk appearance of Nicorandil A common operation in the pharmaceutical industry, used in the manufacture of solid formulations, is powder sieving. When trying to sieve Nicorandil by hand through a mesh size of 0.500mm and 0.710mm to scatter the large and small aggregates, it was noticed that bulk powder was difficult to pass through both meshes. Without the aid of mechanical aids it might be difficult to sieve bulk powder to scatter aggregates, probably due to Nicorandil particle characteristics. These large and small aggregates are an indication that an adequate powder blend homogeneity through dry blending operations might be difficult to achieve. To further evaluate particle morphology microscopic visualization was performed. Three Nicorandil batches (#1, #2 and #3) were observed using an optical microscope according to the method described in the Materials and Methods section (optical microscopy). Figure 15 and Figure 16 show representative images of Nicorandil particles from three batches at different magnifications. Development of oral tablets containing Nicorandil Results and Discussion 51 Figure 15. Nicorandil optical microscopy. Batches #1 and #2 Figure 16. Nicorandil optical microscopy. Batch #3 Particles can be described, generally, as short columnar particles while a small part are plate shaped. There is batch variability regarding particle characteristics since other particle shapes are observed in batches #2 and #3. In these cases particles have acicular shape and a major portion are short columnar particles. Development of oral tablets containing Nicorandil Results and Discussion 52 Particles are translucent with sharp edges and have a smooth surface, although with defects, such as cracks. Images also show the microscopic particle agglomeration that can be observed on the small hard clusters. The effect of grinding on the particles can also be observed. Particles lose their form and appear to be smashed and this behaviour is suggestive of a brittle crystal. Birefringence, which is an indication of crystallinity, was also observed. 1.1.1. Solubility Solubility was determined in duplicate samples. In both cases it was necessary to add up to 10mℓ of purified water to 100mg of powdered Nicorandil to achieve complete solubilisation. Nicorandil is therefore considered sparingly soluble in water. 1.1.2. Apparent density Nicorandil apparent density was determined and evaluated (Hausner ratio and Compressibility Index), according to Ph. Eur., in five batches, as described in the Materials and Methods section. The average and standard deviation results (  ) of five batches are shown in Table 10. Table 10. Apparent density results of Nicorandil Parameter Batch #1 Batch #2 Batch #3 Batch #4 Batch #5 Bulk density (g/mℓ) 0.263 (+ 0.01) 0.422 (+ 0.01) 0.435 (+ 0.01) 0.304 (+ 0.01) 0.247 (+ 0.01) Tapped density (g/mℓ) 0.381 (+ 0.01) 0.530 (+ 0.01) 0.550 (+ 0.01) 0.358 (+ 0.01) 0.314 (+ 0.01) Hausner ratio 1.45 1.26 1.26 1.18 1.27 Compressibility Index 30.97% 20.33% 20.87% 14.9 21.32 Powder flow evaluation Ph. Eur. (2.9.36) “Poor” “Passable” “Passable” “Fair” “Passable” Interpretation of powder flow took into account that this powder forms lumps which create large empty spaces inside the glass tube. Even though classified as Poor and Passable, according to the results shown, Nicorandil seems to have bad flow properties. 1.1.3. Flowability In all five batches tested Nicorandil did not flow freely through the 25 mm nozzles. It requires constant mechanical aid to maintain powder flow, thus flow through 15mm and 10mm nozzles was not performed, as it was assumed that powder would not flow through a smaller hopper. In two batches (#4 and #5) powder did not flow through 25mm nozzle. Results express the average time and standard deviation results (  ) that powder takes to go through the hopper and are indicated on Table 11. Development of oral tablets containing Nicorandil Results and Discussion 53 Table 11. Flowability results of Nicorandil. Time (s) / 100gr Nozzle: 25 mm Batch #1 Batch #2 Batch #3 Batch #4 Batch #5 N 3 3 3 3 3   4.9 s ( 0.38) 7.9 s ( 0.67) 9.5 s ( 0.90) Does not flow Does not flow RSD (%) 7.76 % 11.24 % 9.48% Minimum 4.6 s 7.5 s 8.6 s Maximum 5.3 s 8.7 s 10.4 s Figure 17 illustrates the flow patterns (25mm nozzle) of bulk Nicorandil. Mass of powder is indicated in the Y axis (m [gr]) and time in the X axis (t(s)). Three batches are indicated (batches #1, #2 and #3, from left to right), those in which powder flow could be recorded. Results show the irregular flow which was started and kept by the use mechanical aids. Figure 17. Nicorandil flow pattern Results of apparent density and powder flow suggest that the difficult powder flow of Nicorandil, despite being present in a 10% ratio, must be compensated during formulation with an adequate ratio of excipients with good flow properties since powder flow can influence blend homogeneity, which is a critical issue during formulation, especially in a powder blend for direct compression, that can have a large impact on finished product quality attributes. 1.1.4. Water content Nicorandil has a low water content. Results of Karl Fischer from the Certificate of Analysis indicate an average water content level by Karl Fischer titration method of 0.06% (n=8 + 0.03) with a test specification of NMT 0.1%. Development of oral tablets containing Nicorandil Results and Discussion 54 1.1.5. Particle size distribution Nicorandil particle size distribution was determined by laser diffraction method according with the procedure described in Materials and Methods section. Considering the results of powder density, flowability results and particle characteristics, particle size distribution by analytical sieving was not possible to perform, so to obtain an accurate result fo r the particle size distribution this method was used. The values obtained on three representative batches of Nicorandil are summarized on Table 12. Table 12. PSD results of Nicorandil by laser diffraction Fraction Batch #1 d10 10.36 µm d50 38.78 µm d90 89.04 µm Fraction Batch #2 d10 9.56 µm d50 25.69 µm d90 52.01 µm Fraction Batch #3 d10 7.38 µm d50 23.28 µm d90 52.72 µm Particle size distribution shown refers to three batches used during pharmaceutical development. For comparison purposes additional batches were tested regarding particle size and the results are described in Table 13 (values in micra). From a total of nine batches tested it is possible to observe that Nicorandil particle size distribution has a high batch to batch variation. Development of oral tablets containing Nicorandil Results and Discussion 55 On average, 90% of the particle sizes are below 90µm approximately, although higher values go up to 198.6 micron and as low as 43.0 micron. The average size of the particles is 29.7µm and 10% of the particles are not larger than 9.3µm. Table 13. Nicorandil particle size distribution Fractions (µm) d10 d50 d90 Average (n=9) 9.3 (+4.5) 29.7 (+11.1) 90.3 (+49.2) min 2.6 16.0 43.0 max 14.8 53.3 198.6 1.1.6. Assay and impurity content by HPLC On Table 14, assay and impurities results obtained by HPLC analysis are summarized. This data is representative of nine DS batches analysed and has been compiled for comparison purposes. From each batch two samples were prepared and analysed (see sample preparation for HPLC in Materials and Methods section). Table 14. Assay and impurities results of Nicorandil Parameter Result Assay 100.06% (+ 0.97%) Related substances Nitrate 0.0673% (+ 0.01%) N-(2-hydroxyethyl)-Nicotinamide 0.0453% (+ 0.02%) Imp. A 0.0205% (+ 0.01%) Imp. B 0.0205% (+ 0.01%) Imp C 0.0028% (+ 0.00%) Single unknown impurity 0.0108% (+ 0.00%) Total impurities 0.17% (+ 0.03%) Known impurities standards were analysed and their peaks identified as shown on Figure 18. For comparison purposes a blank and an excipients solution chromatograms were added. It is possible to observe that Nitrate (#1) impurity elutes around 4min and is detected and quantified at 215nm (see HPLC method description in materials and methods section). Next known impurity that elutes is nicotinic acid (#2) around 5min), followed by N-(2hydroxyethyl)-nicotinamide (#3) around 7min and 2-aminoethylnicotinate (Impurity A) (#4) around 9min. Impurity #5, methyl-nicotinate, is a synthesis impurity that elutes around 23min. Nicorandil peak (#6) elutes around 28min and in the gradient phase of the analysis polymeric impurities start to elute, first, impurity B (dimer) (#7) around 42min and later impurity C (#8), around 53min. Development of oral tablets containing Nicorandil Results and Discussion 62 Figure 20. RP 10mg average dissolution profile HPLC assay and impurity results are summarized in Table 18. Table 18. Reference Product assay and impurity results Trade Name Dancor Adancor Batch 5459920 5437234 Assay (n=2) 95.9% (+ 1.35) 95.6% (+ 0.81) Related substances (n=2) Nitrate 0.5888% (+ 0.01) 0.5391% (+ 0.00) Nicotinic Acid 0.0016% (+ 0.00) ND N-2-hydroxyethyl-nicotinamide 0.0167% (+ 0.00) 0.0174% (+ 0.00) Impurity A (2-aminoethyl nicotinate) 0.0869% (+ 0.01) 0.0820% (+ 0.00) Impurity B (Dimer) 0.3705% (+ 0.00) 0.3660% (+ 0.00) Impurity C (Trimer) 0.1021% (+ 0.00) 0.1245% (+ 0.00) Single unknown impurity 0.0441% (+ 0.00) 0.0329% (+ 0.00) Total impurities 1.37% 1.30% Development of oral tablets containing Nicorandil Results and Discussion 63 1.4. Excipients Screening A first selection of excipients was made based on bibliographic data related with their physical and chemical properties to discard those prone to react with the organic groups of Nicorandil and hence accelerate decomposition process, for example, excipients containing crystalline water, that be discarded from a possible formulation., or those which characteristics would not be adequate for the target immediate release solid oral dosage form. An initial screening was based on previous studies published (70-75) on the development of oral dosage forms of Nicorandil. Most of the papers found were related with the development of modified release formulations instead of immediate release, which is the aim of the present study. On Table 19 there is a compilation of the excipients previously used in formulations of Nicorandil found on literature. It describes excipient functionality, references to the studies in which they were used, application of such excipients and decision on whether to use for further studies and corresponding data that justifies such decision. Excipients identified as “potential candidate” refer to excipients that might be advantageous to the stability of the formulation and were selected for additional studies. Excipients excluded are those that by their characteristics do not seem to be appropriate, due to either their organic groups that can be a source of degradation or by other characteristics that were not considered preferential. Table 19. Excipients considered to be used in a Nicorandil formulation Excipient Common function References Decision Justification Isomalt Diluent/filler Potential candidate Can be tested Non hygroscopic excipient suitable for fast disintegrating tablets on direct compression formulations. Chemically stable, low reactivity and low hygroscopicity. Sodium starch glycolate Disintegrant (2 - 8%) Potential candidate Can be tested Very hygroscopic excipient although on a fast disintegration tablet might be necessary to achieve an adequate dissolution rate. Crospovidone Disintegrant (2% - 5%) Potential candidate Can be tested Hygroscopic excipient although on a fast disintegration tablet might be necessary to achieve an adequate dissolution rate. Microcrystalline Cellulose Diluent Disintegrant (74) Can be tested Excipient widely used in direct compression formulations with several grades and particle sizes available. Mannitol Diluent/filler (10% - 90%) (72, 75) Can be tested Non hygroscopic excipient. It has been used in previous works on Nicorandil formulations (51). Pre-gelified Starch Tablet binder in direct compression formulations Tablet disintegrant (2% - 10%) (75) Can be tested Hygroscopic excipient with high water content although has low water activity (76, 77) therefore, it will equilibrate slower when exposed to moisture conditions and may, preferentially, bind the moisture, preventing interaction of water with other components acting as moisture scavenger (78). Development of oral tablets containing Nicorandil Results and Discussion 64 Table 19. Excipients considered to be used in a Nicorandil formulation (continue) Excipient Function References Decision Justification Croscarmellose sodium Disintegrant (0.5% - 5.0%) (75) Can be tested Hygroscopic excipient. Its efficacy might be reduced when used with other hygroscopic excipients in a tablet formulation. Spray dried Lactose Reducing sugar (73) Excluded As a reducing sugar it will likely react with the secondary amine group present in Nicorandil. Sodium bicarbonate Alkalizing agent (73) Excluded Sodium bicarbonate is an alkalizing excipients and higher pH on a solid matrix has been described as a factor that increases degradation rate of Nicorandil. HPMC (K4M, K15, K100M, K200M) Binder Film coating Matrix for ER/MR (70, 72-74) Excluded Hydroxypropyl methylcellulose is an excipient used in oral products, primarily a tablet binder, in film-coating and as a matrix for use in extended-release tablet formulations hence it is not suitable for a fast dissolution profile on an immediate release solid dosage form obtained by direct compression. Cutina HR® ER/MR agent lubricant (72) Excluded This excipient forms a matrix that delays Nicorandil dissolution hence it is not suitable for an immediate release formulation. Ethyl cellulose ER/MR agent (70) Excluded The main use of ethyl cellulose in oral formulations is as a hydrophobic coating agent for tablets and granules. This excipient forms a matrix that delays Nicorandil dissolution hence it is not suitable for an immediate release formulation. Chitosan ER/MR agent (71) Excluded Chitosan is a multipurpose excipient in solid oral formulations that include controlled drug delivery applications, mucoadhesive and rapid release dosage forms. Although, this excipient forms a matrix that delays Nicorandil dissolution hence it is not suitable for an immediate release formulation, besides it has reactive hydroxyl and amino groups and is hygroscopic. Sodium alginate Tablet disintegrant and binder (71, 74) Can be tested This excipient is used as a lubricant and has been referred as a possible improvement on Nicorandil stability due to its compaction properties. Eudragit® L101, Eudragit® RSPO Film coating Matrix for ER/MR (70, 72, 73) Excluded Eudragit® are a class of excipients known as polymethacrylates which are primarily used in oral capsule and tablet formulations as film-coating agents, enteric coatings and sustained release formulations. This excipient is not suitable for an immediate release solid dosage form obtained by direct compression. ER/MR: extended release/modified release Development of oral tablets containing Nicorandil Results and Discussion 65 Table 19. Excipients considered to be used in a Nicorandil formulation (continue) Excipient Function References Decision Justification Dibasic calcium phosphate Diluent (70) Excluded The surface of milled anhydrous dibasic calcium phosphate is alkaline (2) and consequently it should not be used with drugs that are sensitive to alkaline pH. Glyceyl Behenate Lubricant (1.0% - 3.0%) Potential candidate Can be tested Glyceryl dibehenate is a mixture of diacylglycerols, mainly dibehenoylglycerol, and variable quantities of monoand triacylglycerols. It is an excipient that has been described (79) has having good binding properties, it does not affect tablet hardness and is unaffected by mixing or production parameters. Colloidal silica dioxide Glidant (0.1% - 1.0%) (70, 72-74) Can be tested Used in solid oral dosage forms mainly as glidant to improve flow properties of powder. Hygroscopic excipient although due to its affinity to water it can act as a moisture scavenger. Fumaric acid Acidic agent. (72, 74, 80) Excluded Fumaric acid has been described as compatible with Nicorandil although this excipient has been used on two conditions: 2ºC8ºC and 25ºC/60% RH: These results do not guarantee that at higher temperatures or humidity this compatibility with Nicorandil is maintained. Patent information refers a stable Nicorandil formulation using fumaric acid. Since this excipient has already been used it is not going to be considered for further studies. Magnesium stearate Lubricant (70, 74) Excluded The presence of a metallic cation might act as a catalyst on degradation reactions. Calcium stearate Lubricant (75) Excluded Calcium stearate is a mixture of calcium salts of different fatty acids consisting mainly of stearic acid and palmitic acid with minor proportions of other fatty acids. It contains calcium oxide which might be a factor that promotes Nicorandil degradation. Since there are other alternatives, Calcium stearate is not a preferred lubricant. Stearic acid Lubricant (72, 74, 75) Can be tested Stearic acid is a preferred lubricant and one of the excipients that can have a stabilization effect on Nicorandil by protecting the crystalline structure under compression forces. This excipient is also present in the reference product and described in Nicorandil patent although it is mentioned the use of a nonmicronized grade. Selected stearic acid for compatibility studies was a micronized grade. Talc Glidant, diluent, lubricant (72) Excluded Talc is not a preferred lubricant since lubricants based on long aliphatic fat acid chains have been described as having a stabilisation effect on Nicorandil crystalline structure. The information contained on Table 19 helped to select groups of excipients according to their functional class that might be advantageous for a solid oral formulation containing Nicorandil. To achieve a dissolution profile similar to the reference product, which is an immediate release formulation, a fast disintegration must be ensured, hence disintegrant class excipients must be added to the formulation such as sodium starch glycolate, croscarmellose sodium and crospovidone. An excipient with glidant properties such as anhydrous colloidal silica might be used to improve powder flowability if necessary due to the poor flow properties of Nicorandil. Regarding lubricants, glyceryl behenate and stearic acid were considered for compatibility testing. Development of oral tablets containing Nicorandil Results and Discussion 66 1.5. Compatibility Studies Compatibility studies of Nicorandil with selected excipients was done using High Pressure Liquid Chromatography to assess chemical incompatibility with excipients through the quantification of single and total impurity levels. Compatibility studies were done using binary mixtures on a ratio of 1:1 of Nicorandil with excipients and further studies were performed using combinations of excipients with Nicorandil. Before starting the compatibility studies it was necessary to evaluate the effect of selected degradation conditions on Nicorandil DS alone to establish the single (known and unknown) and total amount of impurities across different conditions. The choice of these conditions is important since Nicorandil molecule, as mentioned before, is sensitive to both temperature, humidity and compression forces. It is important to evaluate which are the adequate degradation conditions otherwise it might be possible that too harsh conditions will cause the appearance of degradation products that will not appear during product shelf life. Several published studies, including patents, refer a wide range of temperature and humidity conditions used during Nicorandil degradation studies (45, 51, 80). For the compatibility studies performed in this work maximum temperature selected for degradation studies was 60ºC since it seems that for higher temperatures degradation of Nicorandil is no longer relevant except for forced degradation studies. Regarding humidity a wider values range was evaluated, starting with 0% relative humidity (vacuum chamber until 80% RH. Nicorandil samples were prepared by weighing approximately 100mg of DS directly into glass vials that are then placed in the degradation chambers in the different conditions tested (Table 20) for 8 hours. Conditions #1, #2 and #3 were used since they are ICH degradation conditions for long term, intermediate and accelerated stability studies correspondingly and samples were placed in open vials in climate chambers. Condition #4 was used to evaluate temperature alone, sample was placed inside a closed vial in a vacuum oven. Condition #5 was prepared to evaluate the effect of low moisture and higher temperature. Sample was placed in a closed container with desiccant (silica gel) and humidity was monitored using a calibrated Temperature and Humidity dataloger. Condition #6 was obtained by placing an open vial in a desiccator with a saturated salt solution of potassium chloride. Condition #7 was obtained by adding 10% of purified water (w/w) to the Nicorandil sample and placing it into a sealed vial. For comparison purposes the HPLC results of non-degraded Nicorandil was added. Details on temperature and humidity used as well as results are shown on table Table 20. Development of oral tablets containing Nicorandil Results and Discussion 67 1.5.1. Degradation conditions of Nicorandil Table 20. Degradation conditions of Nicorandil Condition #1 #2 #3 #4 #5 #6 #7 DS Standard (control) Temperature 25ºC 30ºC 40ºC 60ºC 60ºC 60ºC 60ºC Relative humidity 60% 65% 75% 0% 40% 80% Water added Assay (n ≥ 2) 101.08% (+ 0.13%) 101.54% (+ 0.50%) 102.24% (+ 1.52%) 100.46% (+ 0.16%) 100.32% (+ 0.04%) 96.57% (+ 0.10%) 67.21% (+ 2.02%) 100.60% (+ 0.43%) Impurities (n ≥ 2) Known Nitrate 0.0642% (+ 0.01%) 0.0571% (+ 0.00%) 0.0642% (+ 0.01%) 0.1523% (+ 0.02%) 0.1849% (+ 0.08%) 0.5649% (+ 0.10%) 5.9907% (+ 0.50%) 0.0673% (+ 0.01%) A 0.0433% (+ 0.01%) 0.0439% (+ 0.00%) 0.0499% (+ 0.01%) 0.0337% (+ 0.01%) 0.1643% (+ 0.12%) 0.5602% (+ 0.05%) 5.1487% (+ 0.03%) 0.0453% (+ 0.02%) B 0.0218% (+ 0.01%) 0.0236% (+ 0.01%) 0.0206% (+ 0.00%) 0.1328% (+ 0.03%) 0.0807% (+ 0.02%) 0.8748% (+ 0.25%) 11.0327% (+ 0.51%) 0.0205% (+ 0.01%) C 0.0025% (+ 0.00%) 0.0063% (+ 0.00%) 0.0080% (+ 0.02%) 0.0425% (+ 0.02%) 0.0278% (+ 0.00%) 0.1184% (+ 0.20%) 3.1804% (+ 0.22%) 0.0028% (+ 0.00%) Unkn. 1 0.0150% (+ 0.00%) 0.0138% (+ 0.00%) 0.0166% (+ 0.01%) 0.0225% (+ 0.01%) 0.0357% (+ 0.01%) 0.1835% (+ 0.25%) 3.2489% (+ 0.31%) 0.0107% (+ 0.00%) 2 0.0099% (+ 0.00%) 0.0091% (+ 0.01%) 0.0110% (+ 0.00%) 0.0145% (+ 0.00%) 0.0195% (+ 0.00%) 0.0386% (+ 0.10%) 1.5887% (+ 0.14%) 0.0075% (+ 0.01%) 3 <0.01% <0.01% <0.01% 0.0158% (+ 0.01%) 0.0151% (+ 0.00%) <0.01% (+ 0.10%) 1.3863% (+ 0.15%) <0.01% (+ 0.01%) Total impurities 0.16% (+ 0.01%) 0.17% (+ 0.01%) 0.19% (+ 0.03%) 0.43% (+ 0.10%) 0.56% (+ 0.23%) 2.38% (+ 0.28%) 32.27% (+ 0.88%) 0.17% (+ 0.03%) The results obtained seem to indicate that in the ICH degradation conditions there is not a clear indication of degradation in the time period tested (8h). Although when temperature and humidity rises, Nicorandil starts to degrade faster. The effect of temperature alone can be evaluated in condition #4. At high temperature only degradation rate is higher than condition #3 (40ºC/75% RH) which is a sign of the important role of temperature has on Nicorandil degradation rate. Additionally, it is possible to observe that impurities B and C are associated with a temperature increase (condition #4) rather than humidity increase (values in bold) On the other hand, impurity A is more related to humidity increase (condition #5) rather than on temperature increase (value on bold). At the same temperature (60ºC) but increasing the relative humidity, there is an indication that degradation increases judging by the result of total impurities increases. Still keeping the temperature at 60ºC but doubling the relative humidity level (condition #6), increase in total impurities is notorious with approximately 4.5 times folds jump, which might suggest that temperature and humidity can have a synergistic effect on the degradation of Nicorandil (values in bold). The addition of water to Nicorandil sample (condition #7) caused an extensive degradation and results here is no relevance in evaluating these results, since impurities generated are so high that the variations in their profile are unlikely to be significant. Development of oral tablets containing Nicorandil Results and Discussion 68 On Figure 21 and Figure 22 it is possible to observe the impurity peaks in conditions #5 and #6. Figure 21. Nicorandil degradation chromatogram (condition 5) Figure 22. Nicorandil degradation chromatogram (conditon 6) Despite being relatively stable at regular temperature and humidity conditions, for example 25ºC/60%, when left unprocessed (not in the presence of excipients or subjected to mechanical stress (45), there is a range of temperature and humidity were Nicorandil degrades with pharmaceutical relevance. For higher temperature and humidity, the degradation seems to be so extent that has little significance for the evaluation of excipients compatibility. Considering these results the degradation conditions might need Development of oral tablets containing Nicorandil Results and Discussion 69 to be adapted depending on the excipient tested, nevertheless conditions 25ºC/60%, 40ºC/75% and 60ºC/80% at least for 8h, seems to be appropriated degradation conditions. Besides the evaluation of the degradation conditions on Nicorandil, it seems to be relevant to evaluate also the how the DS behaves under mechanical stress (grinding, milling and compaction forces). The purpose of these tests was to simulate the effects that the DS would go through during the manufacture of the final dosage form. 1.5.2. Evaluation of mechanical stress on Nicorandil A mechanical process to reduce the large and small particle aggregates present on Nicorandil bulk powder will likely be necessary to ensure blend homogeneity. Two processes can be used to this end, sieving using an oscillating bar mechanism to force the powder blend through a mesh or a milling process using a rotating mill in blade configuration. Mechanical processing has been described, as previously mentioned, as source of impurity increase due to the damage of the crystalline structure caused by impact forces which, on its turn, causes more entropy in the structure and more free energy available to be used in degradation reactions. To evaluate the effect of both types of mechanical stressing that can potentially can be used during manufaturing, Nicorandil was milled and sieved. These two types or particle reduction methods have been selected since they are common techniques used in the production of pharmaceutical dosage forms. On the other hand, the purpose was also to compare the effect of an attrition method (sieving) with a cutting method on the crystallin structure. Milling trials were done using an Frewitt Hammerwitt at a rotor speed of 60000 rpm (blade configuration) and sieving was done using an oscillating bar sieve attached to an Erweka AR402 module at a speed of 134rpm. Mesh sizes used in both experiments were 0.50mm. Total impurities and assay results (average n≥3) are shown on Table 21. Development of oral tablets containing Nicorandil Results and Discussion 70 Table 21. Effect of milling and sieving on the impurity profile of Nicorandil Compression force Milling Sieving Before degradation Assay 99.52% (+ 1.10%) 99.05% (+ 2.16%) Total impurities 0.23% (+ 0.25%) 0.20% (+ 0.07%) Impurity A 0.1499% (+ 0.15%) 0.0586% (+ 0.03%) Impurity B 0.0142% (+ 0.01%) 0.0113% (+ 0.01%) Impurity C 0.0015% (+ 0.00%) 0.0000% (+ 0.00%) After degradation 60ºC / 80% RH (time = 8h) Assay 95.48% (+ 8.28%) 96.38% (+ 4.09%) Impurity A 0.1489% (+ 0.09%) 0.2022% (+ 0.12%) Impurity B 0.0989% (+ 0.09%) 0.1960% (+ 0.12%) Impurity C 0.0284% (+ 0.02%) 0.0347% (+ 0.04%) Total impurities 0.63% (+ 0.43%) 1.13% (+ 0.81%) Samples were analysed before being degraded at 60ºC and 80%RH and after. The total impurity level seems to be higher when an oscillating bar sieving process is used probably due to a higher friction done on the Nicorandil bulk powder that might cause a higher structural damage. On Figure 23 and Figure 23a, a PXRD difractogram of Nicorandil samples sieved and milled is represented along with Nicorandil DS (not processed). Figure 23. Nicorandil difractogram of sievied and milled samples Development of oral tablets containing Nicorandil Results and Discussion 71 Figure 23a. Detailed view of identified area of figure 22 Generally, diffractograms match at every peak which means that amorphization is not detected. There is although a change on the milled sample (points 1 and 2) with the appearance of two extra peaks. This might be due to a contaminant during sample preparation. Considering the total diffractogram and the consistency of the remaining peaks it is unlikely the occurrence of a change on the crystalline structure. By comparing in detail the peak shape (Figure 22a), it is possible to observe that for the processed samples the peaks are slightly wider that the unprocessed samples which means that more fracture sites (smaller crystalline grain) are present, which is coherent with the induced mechanical stress. 1.5.3. Evaluation of compaction on Nicorandil To assess the impact on Nicorandil crystalline structure of the compaction forces during tableting, a compression test was done on Nicorandil. This test was evaluate by the total impurities level after a degradation stage. Samples were prepared by compacting the DS on a press using diferent compaction pressures and different times of compression. Samples were divided in two compression forces: 0.5 ton, applied during 30s and 2min and 5 ton applied during 30s and 2min. Assay and impurities results were quantified and are presented on Table 22. Development of oral tablets containing Nicorandil Results and Discussion 78 1.6. Excipients selection The excipients to be included in the final formulation were preliminary selected according to a rationale described on Table 29. Optimized qualitative formulation will be discussed during formulation development. Table 29. List of excipients selected for formulation development stage Components Function Rationale Isomalt (GalenIQ 721®) Diluent / filler Formulation main component. Isomalt compatibility results suggest that it has the potential to stabilize Nicorandil molecule. Sodium Starch Glycolate (Vivastar PSF®) Binder / disintegrant Starch pregelatinized has a moisture scavenging property and low water activity which can be used as an advantage on a moisture sensitive formulation. Maize starch (Starch 1500® low moisture grade) Disintegrant Despite being a hygroscopic excipient this disintegrant could be used to accelerate the dissolution profile. A low moisture grade will be used. There are no indication of the use of such starch grade on the patents. Stearic acid (Dub Microlub 50® micronized) Lubricant This lubricant has been identified as a potential stabilization agent to the compaction forces that the Nicorandil crystal suffers durint tableting. Additionally, stearic acid has been described as a preferred lubricant in formulations containing Starch 1500® (79). A micronized grade will be used during formulation development. Patents describe the use of a non-micronized grade of stearic acid. 1.6.1. Excipients description and characterization At this point it was necessary to gather additional information on the excipients properties, which is described hereafter.  Isomalt - GalenIQ 721® Isomalt is the only polyol produced from sucrose and is a mixture of hydrogenated mono and disaccharides whose principal components are the disaccharide alcohols 1-O-α-D-glucopyranosyl-D-mannitol dihydrate and 6-O-α-D-glucopyranosyl-D-sorbitol. It appears as a white or almost white powder or granular or crystalline substance and has good thermal and chemical stability due to its stable glycosidic bond. It does not go through browning reactions and does not possess reducing groups and therefore it is not expected to react with other raw materials in a formulation. Isomalt is non-hygroscopic and at 25ºC does not significantly absorb additional water up to a relative humidity of 85%. As an effect of the low hygroscopicity, tablets produced with Isomalt are more stable than tablets containing other sugar based diluents. This excipient is used in a variety of pharmaceutical preparations including direct compression and wet granulation processes for the production of tablets. Several grades Development of oral tablets containing Nicorandil Results and Discussion 79 of Isomalt marketed under the brand name of GalenIQ® are available, although, type 721 is an excipient especially designed for direct compression due to its higher solubility which produces good disintegration results and has the desirable compaction properties, therefore grade 721 is the grade chosen to be used in formulation development. Since it is a diluent Isomalt will be the major component therefore it is expected to influence the mixture flowability and compaction properties. The compaction properties of the different types of Isomalt are described in the literature (81-83). Evaluation by Heckel plot analysis showed that Isomalt exhibits plastic behavior and undergoes elastic recovery primarily in the die (82). This means that the deformation behavior is similar to sorbitol and mannitol, but differs from the deformation behavior of other polyols such as xylitol and lactitol, which are mainly brittle materials. It has an excellent flowability, does not stick to tableting tools and offers a good compactability. Compression of Isomalt without lubrication is difficult and may cause die wall sticking, capping and lamination. When Isomalt is present in a formulation the addition of a lubricant is recommended.  Sodium Starch Glycolate - Vivastar PSF® low moisture grade Sodium starch glycolate is a substituted derivative of potato starch, rice starch, wheat or corn. Sodium starch glycolate is the sodium salt of carboxymethyl ether and appears as a fine, very hygroscopic, white to off-white, tasteless, odorless, free flowing powder. It can be used in direct compression or wet granulation formulas. Disintegrant properties and mechanism of action are widely described in the literature. The usual concentration employed in a formulation is between 2% and 8%, with the optimum concentration about 4%. SSG has been described as not sensitive to the content of lubricant excipients in a tablet formulation and also to the amount of compression force applied during tableting. Sodium starch glycolate used was Vivastar PSF grade from JRS Pharma which is a special grade with low methanol content especially suited for alcohol and moisture sensitive actives.  Maize starch - Starch 1500®, low moisture grade White or slightly yellow, moderately coarse to fine free flowing, odourless and with a slight characteristic taste powder. Partial pre-gelatinization provides starch with its unique properties. Low moisture grade corn starch has been physically modified with water Development of oral tablets containing Nicorandil Results and Discussion 80 content below 7% and can be directly compressed into tablets. Starch 1500 LM has improved flow and compression characteristics playing multiple functions of binder, disintegrant, flow-aid and self-lubricant in direct compression formulations. The addition of Starch also helps the mixture flows well and decreases the amount of lubricant agents needed due to the self-lubricant properties of pregelatinized starch. The low moisture grade is specially designed to be used with moisture sensitive DS which helps on the long term product stability (78). Besides this characteristic, also showed less absorption rates of moisture compared to common disintegrants such as sodium croscarmelose and sodium starch glycolate. In this study, it was also suggested that starch 1500 has an inhibiting effect on water activity (or equilibrium relative humidity expressed in percentage) within the formulation and retarding moisture interaction with the DS. The same rationale is used to justify the inclusion of starch 1500 since it should preferentially bind moisture and decrease the rate at which the equilibrium relative humidity equilibrates with the environment.  Stearic Acid - Dub Microlub 50, micronized The USP32–NF27 describes stearic acid as a mixture of stearic acid and palmitic acid, defining the content of stearic acid as not less than 40.0% and the sum of the two acids as not less than 90.0%. Stearic acid is a hard, white or faintly yellow-colored, somewhat glossy, crystalline solid with the appearance of leaflets or a white or yellowish white powder. It has a slight fat-like odor and taste. Stearic acid is widely used in oral formulations as a tablet and capsule lubricant. It is insoluble in water, soluble in alcohols and fat solvents. Micronized grade of stearic acid was used to promote an intimate contact with remaining particles so that upon tableting compression forces are deviated from the Nicorandil crystals. 1.7. Excipients risk assessment The second part of the risk assessment focus on the excipients attributes and was performed to evaluate the impact that each component could have on the drug product CQA’s. Considering the excipients selection following the pre-formulation studies an analysis on potential risk that each excipient selected could bring into the formulation and process was done and is described on Table 30. The information contained on this table lists the formulation components and addresses each one following a procedure that Development of oral tablets containing Nicorandil Results and Discussion 81 takes into account materials properties, bibliographic research and characteristics that can have an impact on the finished product quality attributes. Table 30. Risk assessment evaluation on excipients Drug Product CQAs GalenIQ 721® (Isomalt) amount Maiz starch (Starch 1500® LM) amount Vivastar PSF ® (Sodium starch glycolate) amount DUB Microlub 50 (Stearic acid) amount Assay Medium Low Low Medium Degradation Products Low Low High Low Dissolution Medium Medium Medium High Water content Low Medium High Low Hardness High Medium Low Low The justification of the risk assessment for each excipient is described on Table 31. Table 31. Rationale on risk assessment evaluation of formulation excipients Drug Product CQA’s Rationale Risk evaluation Formulation Variables: GalenIQ 721® (Isomalt) amount Assay Isomalt represents the major portion of the formula, therefore, it can have a strong influence on the flow properties of the blend and hence its homogeneity. This, in turn, can impact tablet uniformity of dosage and hence tablet assay. On the other hand since this particular type of Isomalt is especially designed for direct compression formulations, its flow and density properties makes this excipient suitable for this formulation. This variable needs further evaluation. The risk is medium Degradation Products Since Isomalt has a low water content and has low reactivity its influence is not expected to be deleterious to the DS as previously suggested by compatibility studies. The risk is low Dissolution Isomalt represents the major portion of the formula, which can impact at a great extent the compaction properties of the blend. This, in turn, can impact dissolution profile. On the other hand since this particular type of Isomalt is especially designed for direct compression formulations, its flow and density properties makes this excipient suitable for this formulation. This variable needs further evaluation. The risk is medium Water content Isomalt represents the major portion of the formula and this can impact at a great extent the water content of the formulation. Since Isomalt has a low water content and has low reactivity its influence is not expected to be deleterious to the DS as previously suggested by compatibility studies. The risk is low Hardness Isomalt represents the major portion of the formula and this can impact at a great extent the compaction properties of the blend. This, in turn, can impact tablet hardness and cause DS instability. This variable needs further evaluation. The risk is high Development of oral tablets containing Nicorandil Results and Discussion 82 Table 30. Rationale on risk assessment evaluation of formulation excipients (cont.) Drug Product CQA’s Rationale Risk evaluation Formulation Variable: Starch 1500® LM amount. Assay In the recommended amount ranges, starch it is not likely to impact tablet assay. The risk is low Degradation Products Due to starch properties and the demonstrated compatibility, this excipient is expected to have a stability promoter effect on Nicorandil DS. The risk is low Dissolution Starch can impact dissolution due to its functional properties. The amount used must be evaluated to guarantee dissolution profile similarity to the RP. The risk is medium Water content Despite having a water content that can reach 5%, starch properties turns this excipient into a water scavenger inside a tablet matrix. Nevertheless, compatibility studies already performed suggest low interaction with Nicorandil. The risk is medium Hardness Starch is also known for its binding properties. In the range of recommended amounts. Compression trials should be performed to evaluate tablet performance. The risk is medium Formulation Variable: Vivastar PSF® (Sodium starch glycolate) amount. Assay This excipient is not expected to influence the assay values of the drug product. The risk is low Degradation Products SSG is very hygroscopic which can have a negative impact during processing since it has the ability to adsorb moisture from air. Water content is a known factor that increases instability of the DS and the drug product. Further studies should be performed. The risk is high Dissolution SSG level can impact the disintegration time and, ultimately, dissolution profile. Since one of the goals is to match as close as possible the RP dissolution profile a disintegrant might be needed in the formula. Nevertheless, considering the remaining components and the presence of starch, this excipient must be further evaluated. The risk is medium Water content SSG has a high water content value. Despite being present in a small amount, its hygroscopic nature it is necessary to further evaluate this component. The risk is high Hardness This excipient is not expected to influence the tablet hardness. The risk is low Formulation Variable: Stearic acid 50 amount. Assay In the recommended amount levels and by avoiding over lubrication stearic acid has low influence on powder blend flow, therefore it is unlikely to impact tablet assay and CU. The risk is medium Degradation Products This excipient has been identified as a potential promoter of stability by decreasing the compression force on Nicorandil tablets. Compatibility study did not indicate any evidence of a possible interaction with the DS. The risk is low Dissolution Over-lubrication or excessive lubricant may retard dissolution profile. The risk is medium Water content This excipient is not expected to influence total water content of the drug product. The risk is low Hardness This excipient is not expected to influence the tablet hardness. The risk is low Development of oral tablets containing Nicorandil Results and Discussion 83 2. Formulation development The goal of this section is to describe the sequence of tests and results that led to the production a drug product based on the CQA and TPP defined on the Aims of the study section (Table 6). The formulation development encompasses the production of powder blend for direct compression and the production of 10mg Nicorandil round tablets with 7mm in diameter, without scores or embossing. By direct compression it should be understood as the process by which tablets are manufactured by directly compressing powder blends of the active ingredient and suitable excipients. The choice of the manufacturing process is dictated by the stability characteristics of Nicorandil. The known stability issues immediately rule out aqueous based wet granulation, dry granulation or any other process that induces a physical form change on the particles or promotes excessive mechanical stress on its crystalline structure. The manufacturing strategy to formulate Nicorandil tablets will be, therefore, the production of a powder blend for direct compression. Direct compression is a manufacturing process in which a powder blend of the DS and adequate excipients is compressed directly after the blending operation. Direct compression presents challenges related mainly to the particle size of the several components, although shape and density also play important roles (84). If these parameters are sufficiently different between each other the powder blend will tend to present difficult flow and particle segregation phenomena is likely to occur. This poses a threat to the blend homogeneity and tablet content uniformity. Despite being apparently a simple and straightforward manufacturing process, formulating a drug product based on direct compression requires careful evaluation of DS and excipients physical properties to obtain a powder blend with adequate flow properties to allow the powder blend to flow uniformly not only into the tableting machine but also into a die cavity where it will be compressed into a firm compact, or tablet. The tendency of a powder mixture to form a uniform blend or to segregate is also dependent on physical properties such as cohesiveness, particle size and shape or density (1). The homogeneity of the final blend depends on other parameters such as the operating design, DS concentration and raw materials charging sequence as well as blender fill level, mixing time and mixing speed. Development of oral tablets containing Nicorandil Results and Discussion 84 2.1. Manufacturing process risk assessment Before starting the formulation development a risk assessment was done considering that the final purpose was to produce a powder blend for direct compression. The major operations in such manufacturing steps are powder blending, lubrication and tableting. Critical points which can have potential impact on finished product CQA’s and the corresponding risk assessment are listed on Table 32. Table 32. Risk assessment evaluation related with the manufacturing process Process step Assessment Risk evaluation Blending Loading components and DS sieving. Due to PSD of Nicorandil this step should be done with the DS previously sieved gently by hand through a 1mm mesh size to scatter larger aggregates. The risk is low Bending step Blending with Isomalt should be done in two steps to dilute the blend geometrically. Dilution and blending time are critically related to DS homogeneity in the blend. The risk is medium Milling step Milling step is done to guarantee that the DS can be properly blended with the components. The risk is high Lubrication Lubricants are normally used in low amounts and are associated with de-mixing if over blended. For the promotion of an adequate lubricant distribution this should be sieved by hand through a 0,710mm mesh size partially diluted with a blend portion. The risk is medium Final mixture Powder blend will be used to produce 10mg tablets. Blend characteristics must be verified before tableting. The risk is medium Tableting Compression force Compression force (main compression and pre-compression) can influence product performance since it is related to critical quality attributes of the tablets such as resistance to breaking, disintegration, friability and dissolution profile. Additionally, compression force has been associated also with increase in product instability. The risk is low Tableting speed Tableting was done considering only one speed. The risk is low Tablet characteristics Tablets characteristics are an indication of product quality and overall compression process efficiency. Characteristics should meet target product profile defined initially. The risk is medium 2.2. Formulation development studies Formulation development was divided in four trials which started by evaluating its components. Each of these components are identified as formulation variables with potential risk as defined on Table 31. The purpose of the formulation development was to define an optimized manufacturing process able to produce a homogeneous powder blend for direct compression and to produce 10mg Nicorandil tablets. Table 33 summarizes the development process and briefly describes the rationale associated with each step. Development of oral tablets containing Nicorandil Results and Discussion 85 Table 33. Summary of formulation trials Trial Number Number of batches produced Description #1 5 Production of a Nicorandil powder blend to test the influence of sodium starch glycolate on the disintegration times of 10mg tablets to assess its relevance on the formulation. #2 3 Production of a Nicorandil powder blend using different amounts of Starch 1500 PG LM grade to evaluate the effect on 10mg tablets properties. #3 2 Development and optimization of the blending process. Introduction and evaluation of milling trials. Production and characterization of Nicorandil 10mg tablets and evaluation of the compression process. #4 1 Production and characterization of Nicorandil blend and 10mg tablets in a 1kg batch size. Production of samples to start a 3 months stability study. Definition of the final manufacturing process, critical process parameters, risk assessment and final product specifications. The amount of excipients to be used was based on technical bibliography (79) regarding their commonly accepted amount ranges and is described on Table 34. Test regarding changes in the quantitative composition of test formulas will be done inside these ranges. Table 34. Common amounts of selected excipients Component Function % in the formulation Justification Nicorandil DS 10% Target profile GalenIQ 721® (Isomalt) Diluent, filler > 25% Handbook of Pharmaceutical Excipients. Product technical literature. Starch 1500® LM (Pregelatinized starch, low moisture) Binder, disintegrant 2% - 20% Handbook of Pharmaceutical Excipients. Product technical literature. Vivastar PSF® grade (Sodium starch glycolate, low moisture grade) Disintegrant 2% - 8% Handbook of Pharmaceutical Excipients. Product technical literature. Dub MicroLub 50 (Stearic acid, micronized) Lubricant 1% - 3% Handbook of Pharmaceutical Excipients. Development of oral tablets containing Nicorandil Results and Discussion 86 2.2.1. Trial #1 Aim: The purpose of the trial #1 was to assess if sodium starch glycolate (SSG) a very hygroscopic excipient is necessary on the formulation and to which extent its presence influences the disintegration times and the dissolution profile considering that starch, selected to be included on the formulation, also has a disintegrant action on the proposed amount. SSG has been identified as a high risk formulation variable and requires further evaluation regarding the necessity to be included in the formulation. Trial #1 was designed to assess the influence of SSG and is composed of five test mixtures with variable SSG amounts. Manufacturing process: The selected manufacturing process considers the production of five 150g powder blends using a dry blend process for direct compression. Blending operation was done manually using a PE plastic bag. The process started by mixing the DS with SSG and Starch 1500 LM. This pre-blend was mixed in the bag during 3 min and sieved by hand through 0,710mm sieve. Isomalt was added and blended for an additional 3 min. Stearic acid was diluted with two parts of the mixture and hand sieved through a mesh size of 0,5mm and incorporated in the powder blend. The final mixture was blended for 1 min. This mixture was used to produce tablets in an 8 stations lab scale Ronchi® automatic compressing machine using 7mm round, biconvex punches without break line or embossing. The composition of the test mixtures is described on Table 35. Table 35. Trial #1. Quantitative composition of test mixtures Components Formulation #1 Formulation #2 Formulation #3 Formulation #4 Formulation #5 Nicorandil 10% 10% 10% 10% 10% GalenIQ 721® (Isomalt) 75% 73% 71% 67% 63% Starch 1500® PG LM (Pre-gelelatinized starch) 10% 10% 10% 10% 10% Vivastar PSF® (Sodium starch glycolate, low moisture) 0% 2% 4% 8% 12% Dub MicroLub 50 (Stearic acid, micronized) 5% 5% 5% 5% 5% Total 100% 100% 100% 100% 100% Development of oral tablets containing Nicorandil Results and Discussion 87 Variable amounts of SSG were used maintaining fixed the amounts of the remaining components except Isomalt which was used to compensate the variable amounts of SSG. Test #1 does not contain SSG and serves as control sample. Tests #2, #3 and #4 have variable quantities of SSG, 2%, 4% and 8% which are the minimum, optimal and maximum recommended amounts in the literature. Test #5 contains 12% SSG-PSF. Starch 1500® LM was incorporated in the initial formulation as 10% since it is the maximum amount recommended for disintegrant action while maintaining binder properties. The lubricant agent, stearic acid 50 micronized, was used in the amount of 5% based on information retrieved from patent data that indicates stearic acid as an excipient that can help to decrease the compression forces over Nicorandil during tableting. Results: Blending operations were difficult due to the fact that bulk Nicorandil is hard to sieve alone. This is due to the large and small aggregates present in the bulk DS that cannot be scattered by simple dry blending operations. In fact, using a manual sieving step through a 1.0 or 0.710mm mesh sizes, Nicorandil powder alone, without the use of an excipient as a sieving adjuvant, re-agglomerates after the sieving. A pre-blend was performed with Starch to promote Nicorandil dilution and to aid the subsequent sieving step. After the production of the powder blend, the tablets were manufactured by direct compression and were characterized. To evaluate the response of the powder blend to compaction force, compression trials with increasing forces were performed. Compression settings are indicated with values: #150, #125, #100, #75 and #50. Each value represents the distance in millimetres between the main compression rolls on the compression machine. Lower values mean smaller distances and hence a higher compression force is applied between punches. On Table 36 are shown the results (n=20) of hardness testing. Table 36. Trial #1. Compression tests results Compression setting (Main compression force) Test #1 Test #2 Test #3 Test #4 Test #5 Tablet hardness ( + σ) #150 27 N (+ 2) 23 N (+ 3) 25 N (+ 2) 20 N (+ 2) 14 N (+ 2) #125 46 N (+ 5) 56 N (+ 6) 50 N (+ 8) 44 N (+ 9) 35 N (+ 10) #100 115 N (+ 11) 104 N (+ 7) 104 N (+ 4) 89 N (+ 4) 60 N (+ 9) #75 120 N (+ 8) 110 N (+ 11) 107 N (+ 6) 97 N (+ 6) 75 N (+ 4) #50 127 N (+ 9) 114 N (+ 9) 107 N (+ 9) 102 N (+ 10) 84 N (+ 9) Development of oral tablets containing Nicorandil Results and Discussion 94 Tablets were produced with two different compression forces: setting #125 and #105 to evaluate target, low and high tablet hardness. Results from tablet characterization are presented on Table XX: Trial #2 10mg characterization. Characterization tests were performed according to the methodology described in the Materials and Methods section, results are summarized in Table 41. Table 41. Trial #2. 10mg tablets characterization results Mixture number Test #1 Test #2 Test #3 Test #1 Test #2 Test #3 Compression setting #125 #105 Hardness 60 N 55 N 29 N 100 N 97 N 85 N Friability 0.37% 0.39% 0.40% 0.22% 0.23% 0.36% Dissolution (% at 30min) 100.8% 99.7% 100.7% 101.2% 98.5% 99.1% Disintegration Time (n=6) First: (mm:ss) 3:30 3:27 2:40 4:05 4:00 2:40 Last: (mm:ss) 4:15 3:40 3:10 4:25 4:20 3:10 Tablet weight (n=10) Average 99.8 100.5 98.6 100.9 99.5 99.82 min 97.3 99.5 97.6 98.0 97.9 97.10 max 102.3 101.3 99.3 102.5 101.2 102.7 RSD 1.35% 0.62% 0.61% 1.47% 1.28% 2.10 Tablet thickness (n=10) (mm) 2.59 2.62 2.62 2.51 2.50 2.51 RSD (%) 0.97% 0.49% 0.39% 1.44% 0.76% 0.75% When compared with trial #1, tablets without SSG-PSF (test mixture #1) have higher hardness for the same compression force used. The effect on disintegration times when SSG PSF increases is evident and it can be concluded that this excipients is accelerating as expected the disintegration time. Reducing starch from 10% to 5% (from trial #1 to trial #2) seems to produce tablets with higher hardness for the same compression force applied. On Figure 28 and Figure 29 dissolution profiles are shown and compared with the RP. Development of oral tablets containing Nicorandil Results and Discussion 95 Figure 28. Trial #2. Dissolution profiles of tablets from mixtures 1, 2 and 3 Figure 29. Trial #2. Dissolution profiles of tablets from mixture 1 and RP When comparing the dissolution profiles it is possible to observe that tablets produced from trial #2 mixture are similar to the dissolution profile of both RP batches (Figure 29) and tablets produced from mixture #2 and #3 show slower dissolution rates. Development of oral tablets containing Nicorandil Results and Discussion 96 2.2.3. Trial #3 Aim: The purpose of trial #3 was to produce a powder blend using a milling step to promote optimal blend homogeneity and to produce and characterize tablet performance. During DS characterization it was noticed that bulk Nicorandil presented large, soft and sticky agglomerates. Previous trials confirmed that Nicorandil will hardly blend with excipients without the use of a mechanical process. Even in a smaller scale, agglomeration is present and it is possible to observe small and hard grain like agglomerates that would unlikely be scattered by simple dry blending operations. Since it became necessary to scatter these agglomerations and microscopic aggregates, a milling step was introduced in the manufacturing process. As already suggested by pre formulation tests a milling seems to induce less damage on Nicorandil crystalline structure than the oscillating bar sieving process which causes more friction (Table 21). Manufacturing process: The selected manufacturing process considers the production of one 500g powder blend using a dry blend process for direct compression. Blending operation was done using a double cone blender. The first raw material to be added to the bin is Isomalt (10%), next Nicorandil followed by Starch 1500 PG LM grade to promote an intimate contact by starch particles. This sequence allows a geometric dilution of Nicorandil. This pre-blend was mixed and afterwards the remaining amount of Isomalt was added followed by another mixing step. By last, the mixture can be lubricated with stearic acid 50 micronized previously diluted with two parts of the mixture and hand sieved through a mesh size of 0,5mm. Blend homogeneity was assessed by collecting 4 samples from approximately equidistant points on the bin using a thief probe in the preblend (before lubrication) an in the final blend. Tablets were produced in an 8 stations lab scale Ronchi® automatic compressing machine. The composition of the mixture is described on Table 42. Table 42. Trial #3. Qualitative composition Components Quantitative composition Nicorandil 50g 10% GalenIQ 721® (Isomalt) 375g 75% Starch 1500® PG LM (Pre-gelelatinized starch) 5g 10% Dub MicroLub 50 (Stearic acid, micronized) 2.5g 5% Total 500g 100% Development of oral tablets containing Nicorandil Results and Discussion 97 An optimal blending process can be achieve by testing different blend times and sampling powder blend to assess content homogeneity. The first blending operation was done in 5 minutes intervals until 15 minutes total blending time was reached. At each interval the mixture was inspected for the existence of lumps or aggregates. The same procedure was repeated after the milling step where different rotor speeds were tested. Two additional blending steps following a geometric dilution procedure were tested. At this stage, in both steps after milling a mixture homogeneity was performed. Lubrication time was also tested with different blending times and at the end mixture homogeneity, flow properties, particle size distribution, density and water content was determined. The tablets obtained from this mixture were also studied regarding physical properties and dissolution. Manufacturing process sequence, settings, controlling and equipment used are described on Table 43: Table 43. Trial #3. Process summary table Stage Machine/Description Settings Controlling Blending (Pre Blend) Erweka module Speed: 34 rpm Double cone blender Check rotation speed Mixing step #1 5 min + 5 min (total 10min) + 5 min (total 15min) Check blending time Visual inspection Hammerwitt Speed: to be defined Mesh size: to be defined Visual inspection PSD Blending (Blend) Erweka module Speed: 34 rpm Double cone blender Check rotation speed Mixing step #2 5 min + 5 min (total 10min) + 5 min (total 15min) Check blending time Mixture homogeneity Mixing step #3 10 min + 10 min (total 20min) + 5 min (total 25min) Check blending time Mixture homogeneity Blending (Final Blend) Sieve (to sieve stearic acid) 0.500 mm Check sieve size and integrity Erweka module Speed: 34 rpm Double cone blender Check rotation speed Mixing step #4 (lubrication) 3 min + 2 min (total 5min) + 3 min (total 8min) Mixture homogeneity Flowability Powder density PSD Compression Ronchi 8 station rotary press Lab scale tableting machine Main compression: to be defined Pre-compression: to be defined Filing: to be defined Hardness Disintegration time Friability Dissolution Development of oral tablets containing Nicorandil Results and Discussion 98 The next flowchart summarizes the manufacturing steps taken. Development of oral tablets containing Nicorandil Results and Discussion 99 During the initial blending step it was possible to observe larges agglomerates of Nicorandil in the powder blend at every 5 minutes interval. At the end of the 15min blending time some smaller size agglomerates remained scattered in the powder blend. This mixture was milled at different speeds without the use of a mesh. Samples were analysed regarding PSD for each speed tested. The results are shown in Figure 30 were it is possible to observe the variation on the PSD (micra) with the increase in the milling speed (x1000 rotations per minute). Figure 30. PSD results of milling trials Only at higher speeds it is possible to reduce particle aggregates that become retained on 1mm sieve (square markers). These aggregates are formed by Nicorandil particles and its presence can compromise blend homogeneity. Since it is not possible to completely eliminate grain like particles even using maximum speed an additional test was performed using this time a mesh size of 0,6mm. The results are expressed on Figure 31 using the same representation as in Figure 30. Development of oral tablets containing Nicorandil Results and Discussion 100 Figure 31. PSD results of milling trials (with mesh) Using a 0,60mm mesh during milling helped to reduce the small Nicorandil aggregates even at slower speed (square marker) as is suggested on Figure 31. To this milled powder blend Isomalt was added and blended in two steps. This action is done to geometrically dilute the initial powder blend according to the manufacturing process described. The final mixture was characterized. The results are described on Table 44. Table 44. Trial #3. Mixture characterization results Test Pre blend Final blend Density Bulk 0,583 0,570 Tapped 0,757 0,735 Hausner Ratio 1,30 1,29 Compressibility Index 22,92 22,4 Evaluation Passable Passable Flowability (Time (s) / 100gr) Nozzle (mm) 25 15 10 25 15 10 Average (s) 6,5 16,5 NP 6,2 14,5 NP St. Dev (s) 0,10 3,42 NP 0,10 3,20 NP RSD (%) 1,55% 20,72% NP 1,30% 18,50% NP Powder blend presents a passable flow characteristic. Flow through hopper (25mm) was constant and steady although when using a 15mm hopper flow was more difficult and irregular. When 10mm hopper was used powder did not flow. Final mixture particle size distribution by analytical sieving was determined (Figure 32. Development of oral tablets containing Nicorandil Results and Discussion 101 Figure 32. Trial #3. Mixture particle size distribution This powder blend is characterized by a low particle size with 50% of the particles bellow 182micra. Blend homogeneity was determined using the in house UV method as described in Materials and Methods section. Powder blend was sampled in six points directly into a 200mℓ volumetric flask according to the diagram on Figure 33. Figure 33. Trial #3. Mixture sampling diagram Each sampling point was measured 4 times. Average and relative standard deviation results are summarized in Table 45. Development of oral tablets containing Nicorandil Results and Discussion 102 Table 45. Trial #3. Mixture homogeneity results Stage Time Assay RSD Blending step #2 5 min 100.45% 2.64% 10 min 100.86% 1.30% 15 min 100.58% 0.98% Blending step #3 10 min 99.59% 3.35% 20 min 101.06% 2.09% 25 min 99.01% 1.20% Final mixture 3 min 101.19% 1.58% 5 min 101.56% 0.96% 8 min 100.16% 0.88% Results suggest that homogeneity improves with longer processing times judging by the results of relative standard deviation. Lubrication step does not seem to promote demixing with longer blending times. The final powder sampled was compressed into 10mg tablets using different compression forces. Characterization results are summarized on Table 46. Table 46. Trial #3. Tablets characterization results Compression setting #105 #115 #125 #135 Weight (n=10) 100mg 100mg 100mg 100mg Hardness 61N 45 N 40 N 18 N Disintegration time First 3min 43s 4min 15s 2min 48s 3min 21s 3min 30s 3min 57s 2min 19s 3min 16s Last Friability 0.23% 0.38% 0.41% 0.59% Dissolution (%) 96.9% (0.62%) Not performed 100.5% (1.08%) Not performed Compression setting #125 and #105 produced tablets with an average of 40N and 61N respectively which were used for a dissolution test (Figure 34). Development of oral tablets containing Nicorandil Results and Discussion 103 Figure 34. Trial #3. 61N and 40N tablets dissolution test Considering the results obtained in this trial, the process parameters included on Table 47 will be tested on an increase powder blend amount. Table 47. Manufacturing parameters to be tested on trial #4 Stage Machine/Description Settings Blending (Pre Blend) Erweka module Speed: 34 rpm Double cone blender Mixing step #1 10min Hammerwitt Speed: to be defined Mesh size: to be defined Blending (Blend) Erweka module Speed: 34 rpm Double cone blender Mixing step #2 10min Mixing step #3 15min Blending (Final Blend) Sieving step (to sieve stearic acid) 0.500 mm Erweka module Speed: 34 rpm Double cone blender Mixing step #4 (lubrication) 5min Compression Ronchi 8 station rotary press Lab scale tableting machine Main compression: to be defined Pre-compression: to be defined Filing: to be defined Setting for milling and compression force will be defined at the end of Trial #4, depending on the outcome. Development of oral tablets containing Nicorandil Results and Discussion 110 Table 52. Final risk assessment on DS attributes Drug Product CQA’s Rationale Risk evaluation DS Attributes: Particle Size Distribution Assay Throughout the develppment work all assay results complied with expected results. Milling trials performed on powder mixtures also did not indicate any assay problems. The risk was reduced from medium to low. Low Degradation Products There were no indication that PSD could negatively affect DS stability. The risk was reduced from medium to low. Low Dissolution All dissolution tests performed showed fast dissolution profile. These results support the low risk assignment relating dissolution and particle size distribution. The risk was reduced from medium to low. Low Water content DS PSD is an intrinsic phsical property which is not related with the water content of the drug product. During development work described no evidences have been found that could relate this two parameters. The risk was unchanged. Low Hardness PSD of the DS does not seem to have relevant influence on tablet hardness results, mainly due to the remaning components of the formulatin which characteristics have much more weight on the comapction properties of the powder blend. The risk was unchanged. Low DS Attributes: Solubility Assay Throughout the develppment work all assay results complied with expected results. Sink conditions have been demosntrated to comply with pharmacopoeial standards. The risk was unchanged. Low Degradation Products There is no indication that solubility can negatively affect DS stability. The risk was unchanged. Low Dissolution All dissolution tests performed showed fast dissolution profile. These results support the low risk assingnment relating dissolution and solubility. The risk was reduced from medium to low. Low Water content There is no relationship between solubility and water content. The risk was unchanged. Low Hardness Solubility of the DS does not seem to have relevant influence on tablet hardness results. The risk was unchanged. Low DS Attributes: Chemical Stability Assay Nicorandil stability is a major issue when formulating a drug product with this molecule. A carefull monitoring of raw materials properties, manufacturing process and packaging is necessary to avoid excessive exposure of the DS and drug product to conditions that can promote degradation reactions. The risk was reduced from high to medium. Medium Degradation Products Dissolution Even at accelerated conditions the Nicorandil tablets maintain a fast dissolution behaviour. Nevertheless additional stability data seems to be necessary to further investigate dissolution performance. The risk was reduced from high to low. Low Water content Water content and relative humidity must be carefully monitored to avoid excessive exposure to water. The risk was reduced from high to medium. Medium Hardness Tablet hardness must be kept at a minimum possible to reduce the a negative effcet on crystalline structure of Nicorandil. The risk was reduced from high to medium. Medium DS Attributes: Flowability Assay Flow properties do not seem to be influencing assay results. The risk was reduced from medium to low. Low Degradation Products DS flow properties are not directly related to drug product impurity level. The risk was unchanged. Low Dissolution Flowability of the DS has been properly compensated during formulation development and had no visible impact on dissoloution profile. The risk was reduced from medium to low. Low Water content DS flow properties are not directly related to drug product water content. The risk was unchanged. Low Hardness DS flow properties are not directly related to tablet hardness or to an extent that requires further evaluation. The risk was unchanged. Low Development of oral tablets containing Nicorandil Results and Discussion 111 3.1.2. Excipients Table 53. Final risk assessment on excipients attributes Formulation Variables Drug Product CQA’s Rationale Risk evaluation GalenIQ 721® (Isomalt) Assay Isomalt seems to be an adequate component (diluent) on the formulation. Results do not seem to indicate any negative efefct on drug product CQA’s. All paramters risk has been reduced to Low level. Low Degradation Products Low Dissolution Low Water content Low Hardness Low Starch 1500® LM Assay This excipient does not seem influence the assay results. The risk was reduced from medium to low. Low Degradation Products A low moisture grade was used on the formulation although it seems that additional studies might be necessary to evaluate the effect of starch on the proposed concentrations on the formulation. The risk has been increased from low to medium. Medium Dissolution Despite the binding / disintegrant properties of starch it seems that additional studies might be necessary to evaluate the effect of starch on the proposed concentrations on the dissolution behaviour on the long term stability. The risk was unchanged. Medium Water content A low moisture grade was used on the formulation although it seems that additional studies might be necessary to evaluate the effect of starch on the porposed concentrations on the formulation. The risk was unchanged. Medium Hardness This componet does not seem to negatively influence tablet hardness. The risk was reduced from medium to low. Low Stearic acid 50 Assay Stearic acid does not seem to have a negative effecto on any of the CQA’s of the drug product. All paramters risk has been reduced to Low level. Low Degradation Products Low Dissolution Low Water content Low Hardness Low Development of oral tablets containing Nicorandil Results and Discussion 112 3.1.3. Manufacturing process Table 54. Final risk assessment on manufacturing process Process step Assessment Control strategy Risk evaluation Blending Loading components and DS sieving. Due to PSD of Nicorandil this step should be done with the DS previously sieved gently by hand through a 1mm mesh size to scatter larger aggregates. Nicorandil should be added in between Starch and SSG-PSF grade to promote a better DS distribution. A simple visual inspection is adequate to verify that most of DS aggregates have been scattered. No impact on final blend homogeneity is expected. Low 5 min. bending step Blending step introduced to prepare the pre-mixture for the milling step. A simple visual inspection is adequate to verify that the resulting blend appears to have the DS scattered. No impact on final blend homogeneity is expected. Low Milling step Milling step is done to guarantee that the DS can be properly blended with the other components. In the settings used. Milling speed: 30 to 60rpm (x1000). Mesh size: 0,60mm. Low Addition of Isomalt and 30 min blending step Blending with Isomalt should be done in two steps to dilute the blend geometrically. Dilution and blending time are critically related to DS homogeneity in the blend. Mixture homogeneity must be performed before lubrication step to verify DS homogeneity and the need to additional blending time. Low Addition of lubricant and 5min blending step Lubricants are normally used in low amounts and are associated with de-mixing if over blended. To promote an adequate lubricant distribution this should be sieved by hand through a 0,710mm mesh size partially diluted with a blend portion. Mixture homogeneity must be performed to verify DS homogeneity. Low Final mixture Powder blend will be used to produce 10mg tablets. Blend characteristics must be verified before tableting. Mixture homogeneity must be performed to verify DS homogeneity. Additionaly, blend characterization must be performed. Low Tableting Compression force Compression force (either main compression and precompression) can influence product performance since it is related to critical quality attributes such as resistance to breaking, disintegration, friability and dissolution profile. Additionaly, compression force has been associated also with increase in product instability. Compression forces must be low enough to obtain tablets with desirable characteristics. Low Tableting speed Tableting was done considering only one speed. Check tableting speed. Low Tablet characteristics Tablets characteristics are an indication of product quality and overall compression process efficiency. Characteristics should meet target product profile defined initially. IPC should be done at regular intervals during manufacturing process. Low Development of oral tablets containing Nicorandil Results and Discussion 113 3.2. Similarity assessment To assess the influence of stability conditions and time on the dissolution performance, results were statistically evaluated at different times (10, 15 and 30min). Statistical analysis used is described in the Materials and Methods section. Dissolution profiles were plotted by comparing tablets with the same hardness along the time and also between different conditions against two batches of the RP, although for the purpose of evaluation and to detect differences of performance between the two hardness statistical evaluation considers all samples. On Figure 37, the dissolution profiles of 30N samples stored at 25ºC/60% RH and 40ºC/75% RH during the 3 months stability study and two batches of the RP are shown. Figure 37. Average dissolution profiles of 30N tablets vs RP On Figure 38, the dissolution profiles of 60N samples stored at 25ºC/60% RH and 40ºC/75% RH during the 3 months stability study and two batches of the RP are shown. Development of oral tablets containing Nicorandil Results and Discussion 114 Figure 38. Average dissolution profiles of 60N tablets vs RP Evaluation of the dissolution profiles of 30N tablets samples show that dissolution rate decreased in the 40ºC/75% RH after 1 month (T1M) and 3 months (T3M) and the dissolution profile in these two conditions is very approximate. As for the 25ºC/60% RH condition, profiles seem to be also very similar and almost match the initial time (T0). Considering that the product still exhibits a fast dissolution profile it might be possible to assume that all DS is released and solubilized before the stomach emptying time (30min). Evaluation of the dissolution profiles of 60N tablets samples show that dissolution rate decreased after 1 month (T1M) in both degradation conditions. After 3 months (T3M) at 40ºC/75% RH the profile is equivalent to the one at T1M in the same condition. Nevertheless, the product still shows a fast dissolution profile so it might be possible to assume that all DS is released and solubilized before the stomach emptying time (30min) even at the end of the short term stability study. To evaluate similarity of dissolution profiles a statistical comparison of the results of dissolved amounts at 10, 15 and 30min was done. These results allow to conclude that there are some statistical differences in the comparison times although in terms of pharmaceutical performance these differences are not likely to have an impact on the biological availability of the DS in the bloodstream. Development of oral tablets containing Nicorandil Results and Discussion 115 Considering that the disintegration times are under 5min and to discard the variability induced by this physical phenomenon, dissolution profiles were compared at 10min, 15min and 30min. At 10min, tablets are fully disintegrated so we assume that performance is now dictated by dissolution behavior only, which is influenced, on its turn, by the solubility of the DS. Dissolution at 15 minutes was also used for comparison purposes to evaluate differences for the RP which demonstrates a very fast dissolution profile (87). At 10 minutes the samples can be divided in four groups with statistical differences between them (subsets 1 to 4) as described in Table 55. To evaluate these differences a box plot representation is shown, where it is possible to observe that all samples at 40ºC/75% RH stand aside the remaining samples (Figure 39). When comparing with both batches of the RP it is possible to conclude that dissolution data at 10min is statistically similar to the 30N tablet values in the 25ºC/60% RH in all time points, while the remaining samples present significate differences from the RP. Figure 39. Box plot of dissolution results at 10min 30N and 60N vs RP Table 55. 10min dissolution Tukey HSD results Samples Subset for alpha = 0.05 1 2 3 4 Lt#2 60N T1M 40_75 65.0897 Lt#2 30N T3M 40_75 69.2589 69.2589 Lt#2 60N T3M 40_75 69.5887 69.5887 Lt#2 30N T1M 40_75 70.7537 Lt#2 60N T1M 25_60 81.8686 Lt#2 60N T0M 84.6200 Lt#2 60N T3M 25_60 85.5925 Lt#2 30N T1M 25_60 90.6523 Lt#2 30N T3M 25_60 91.5079 Lt#2 30N T0M 93.2803 RP 54599 20 94.3667 RP 54372 34 95.0167 Significance 0.063 0.994 0.233 0.081 Development of oral tablets containing Nicorandil Results and Discussion 116 The next critical point analyzed was at 15minutes. In this time the samples can be divided in five groups with statistical differences between them (subsets 1 to 5) as described in Table 56, although more samples are statistically similar to the RP. To evaluate these differences a box plot representation is shown, where it is possible to observe that all samples at 40ºC/75% RH still stand aside the remaining samples (Figure 40). When comparing with both batches of the RP it is possible to conclude that dissolution data at 15min is statistically similar to the 30N and 60N tablet values in the condition 25ºC/60% RH in all time points, while the remaining samples present significate differences from the RP. This suggest that the differences caused in the dissolution profile by increased hardness are fading away. Figure 40. Box plot of dissolution results at 15min 30N and 60N vs RP Table 56. 15min dissolution Tukey HSD results Samples Subset for alpha = 0.05 1 2 3 4 5 Lt#2 60N T1M 40_75 77.9595 Lt#2 30N T3M 40_75 82.1284 Lt#2 60N T3M 40_75 83.9882 83.9882 Lt#2 30N T1M 40_75 85.9201 92.3188 Lt#2 60N T1M 25_60 94.4833 94.4833 Lt#2 60N T0M 94.9304 94.9304 Lt#2 60N T3M 25_60 95.5000 95.5000 Lt#2 30N T1M 25_60 95.5478 95.5478 Lt#2 30N T3M 25_60 96.9107 Lt#2 30N T0M 97.7784 RP 54599 20 98.0175 RP 54372 34 99.0234 Significance 1.000 0.872 0.842 0.165 0.087 Development of oral tablets containing Nicorandil Results and Discussion 117 The last time point analyzed was at 30minutes. In this time the samples can be divided in three groups with statistical differences between them (subsets 1 to 3) as described in Table 57. 30min dissolution Tukey HSD resultsThe graphic representation of these differences is shown on a box plot, where it is possible to observe that RP samples are different from all other samples except for 30N tablets at 3 months in the 40ºC/75% RH samples. This is due to the fact that the RP does not reach 100% dissolution at 30 minutes dissolution time and instead has 95% (Figure 41). Figure 41. Box plot of dissolution results at 30min 30N and 60N vs RP Table 57. 30min dissolution Tukey HSD results Samples Subset for alpha = 0.05 1 2 3 RP 54599 20 94.4833 Lt#2 30N T3M 40_75 95.4480 RP 54372 34 95.5333 Lt#2 60N T3M 40_75 97.1925 97.1925 Lt#2 60N T1M 40_75 99.0176 99.0176 Lt#2 30N T1M 40_75 99.1605 99.1605 Lt#2 30N T3M 25_60 99.9335 99.9335 Lt#2 60N T1M 25_60 99.9547 99.9547 Lt#2 60N T3M 25_60 100.3397 Lt#2 30N T0M 100.4654 Lt#2 60N T0M 100.6020 Lt#2 30N T1M 25_60 100.9409 Significance. 0.141 0.124 0.615 As mentioned before these differences have less importance since all dissolution profiles are still very fast which means that DS is completely dissolved before 30min. In practical terms, these results suggest that the bioequivalence between test tablets should be the same as the RP. Development of oral tablets containing Nicorandil Results and Discussion 118 3.3. Stability assessment Concerning the short term stability the selected tests to evaluate product stability and pharmaceutical performance were: DS assay, impurity assessment (single known and total), dissolution, disintegration time, hardness and water content (KF). Table 58 summarizes the results obtained at each time and in each condition. Dissolution and Water Content (KF) were not performed for the intermediate condition at 1 month and 3 months since the information gathered from these two points was not considered necessary taking into account the drug product performance characteristics. It is assumed that long term (25ºC/60%RH) and accelerated conditions (40ºC/75%RH) are representative of drug product stability and the results obtained at those time points can be used to assess performance in intermediate conditions, according to international guidelines on stability (16) and matrixing and bracketing (88). In case of any odd results in disintegration times and water content at extreme conditions, intermediate samples would be analyzed. Table 58. Tests performed during stability study Tests to perform T0 T1M T3M 25ºC/60%RH 30ºC/65%RH 40ºC/75%RH 25ºC/60%RH 30ºC/65%RH 40ºC/75%RH Assay Yes Yes Yes Yes Yes Yes Yes Impurities Yes Yes Yes Yes Yes Yes Yes Disintegration Yes Yes Yes Yes Yes Yes Yes Dissolution Yes Yes No Yes Yes No Yes Water content Yes Yes No Yes Yes No Yes Resistance to crushing Yes Yes Yes Yes Yes Yes Yes Stability testing was performed on 10mg Nicorandil tablets packed in Alu-Alu blister. This packaging material is a special designed multilayered ultra-high barrier laminate film with a polyolefin sealant layer incorporating moisture scavenging agent / desiccant in the inner layer of the aluminum foil. Tablets in the blister are therefore in contact with a surface that adsorbs moisture from the air inside the pocket. Table 59 and Table 60 presents the overall results for 30N and 60N test product, correspondingly. Parameters evaluated were assay, known and unknown impurities, total impurities, disintegration, dissolution, water content (KF) and tablet hardness. Development of oral tablets containing Nicorandil Results and Discussion 119 Table 59. Summary of stability results of test formulation (30N) Parameter Testing point (month) / results T0 T1M T3M RP 30N 25ºC/60% RH 30ºC/65% RH 40ºC/75% RH 25ºC/60% RH 30ºC/65% RH 40ºC/75% RH RP 30N RP 30N RP 30N RP 30N RP 30N RP 30N Assay 96.9% 101.05% 98.7% 101.21% 96.9% 100.25% 88.60% 94.01% 96.3% 100.44% 94.70% 103.81% 85.80% 85.36% Nicotinic acid ND ND ND ND ND ND ND < 0.1% ND ND ND ND ≤ 0.1% < 0.1% N-(2 hydroxyethyl) Nicotinamide ND < 0.1% ND < 0.1% ND < 0.1% ≤ 0.1% < 0.1% ND ND ND ND ≤ 0.1% < 0.1% Imp A ≤ 0.1% < 0.1% ≤0.1% < 0.1% ≤ 0.1% < 0.1% 0.16% 0.1005% ≤ 0.1% 0.1507% ≤ 0.1% 0.1123% 0.32% 0.0221% Imp B 0.20% < 0.1% 0.37% 0.2547% 0.45% 0.3702% 0.68% 1.0113% 0.42% 0.4657% 0.47% 0.5530% 0.53% 1.3454% Imp C 0.21% < 0.1% ≤0.1% < 0.1% 0.29% 0.1331% 0.55% 0.6055% 0.26% 0.0331% 0.35% 0.3292% 0.58% 1.1240% Nitrate NP 0.0903% NP 0.1348% NP 0.2116% NP 1.2876% NP 0.3833% NP 0.7985% NP 4.2523% Single unknown imp. ≤ 0.1% 0.03% ≤0.1% 0.02% ≤ 0.1% 0.03% 0.30% 0.64% ≤ 0.1% 0.07% ≤ 0.1% 0.25% 0.36% 0.68% Total impurities (except Nitrate) 0.41% 0.23% 0.37% 0.43% 0.74% 0.67% 1.90% 2.93% 0.68% 0.83% 0.82% 1.35% 2.60% 3.91% Disintegration 2min 50s 3 min 15s 3min 05s 3min 30s 2min 00s 2min 29s 3min 10s 3min 30s 1min 00s 1min 18s NP 1min 25s 1min 42s 3min 55s 4min 35s 1min 10s 1min 33s 2min 55s 3min 45s 1min 20s 1min 45s 3min 59s 4min 43s 2min 35s 2min 56s 4min 09s 4min 50s Dissolution 98% 100.6% 98% 98.6% 98% NP 97% 97.9% 99% 98.5% 98% NP 95% 93.7% Water content (KF) 0.3% 2.1% 0.2% 2.2% 0.2% 2.5% 0.2% 2.8% 0.3% 2.0% 0.3% 2.0% 0.3% 1.9% Resistance to crushing 61 N 29N 56 N 30N 66 N 34N 64 N 45N NP 31N NP 37N NP 46N Development of oral tablets containing Nicorandil 126 Development of oral tablets containing Nicorandil Conclusions 127 1. General conclusions The present work described the pre-formulation and formulation development that led to the production of 10mg tablets of Nicorandil by direct compression of a homogeneous powder blend. The manufacturing process has been demonstrated to be able to produce a finished product that presents adequate pharmacotechnical characteristics and presents performance characteristics similar to the reference product. Nicorandil is highly sensitive to moisture and compaction forces, reaching high degradation rates when included in a formulation, which is potentiated at increased temperatures. A three months short term stability study was performed. Various critical properties were assessed and compared to the reference drug product. Evaluation of the results of the tested parameters suggest that over the time period of the study, no relevant differences in terms of performance and stability between the test product and the reference drug product were observed. Despite this analysis, it is clear that due to the unstable nature of Nicorandil, ICH accelerated conditions might not be adequate to support expiry date of the finished product. Nevertheless, results obtained on the RP also indicate the same degradation trend. The main principles that guided this work were: 1. Detailed research on available scientific bibliography and patents in order to collect information that could be used to optimize the development process. 2. Definition of a Target Product Profile and the Critical Quality Attributes of the drug product to define a development strategy. 3. Application of a risk management tool during the development process. 4. Characterization and evaluation of the DS properties before manufacture. 5. Careful selection and characterization of excipients in order to maximize Nicorandil stability. 6. Selection of adequate process parameters to avoid unnecessary risks linked to stability issues of the DS. 7. Selection of a packaging material constituting an effective barrier against moisture. Development of oral tablets containing Nicorandil Conclusions 128 The main achievements of this work can be summarized as the following: 1. A simple and robust manufacturing process, advantageous for industrial production, was designed and it was demonstrated that it allows the production of a homogeneous powder blend with adequate flowability and compressibility. 2. Tablets with adequate pharmacotechnical properties and content uniformity can be obtained by direct compression of the powder blend. 3. Formulation seems to protect Nicorandil within an interval of compression forces (up to 60 N). This work also demonstrated that the control strategy applied on the manufacturing process was adequate to guarantee the compliance with the quality targets defined. It is possible to conclude also that specific control strategies must be followed, such as: 1. The initial properties of the DS must be carefully evaluated. Characteristics such as water content, initial impurity levels and PSD must be specified and batches not complying with specifications must be rejected for manufacture. 2. Excipients must be also controlled regarding critical parameters, like water content and PSD. 3. Environmental conditions on manufacture areas must be adjusted, meaning that it is recommended that temperature should be kept at least bellow 25ºC and relative humidity levels should be as low as possible. 4. Tablets should have a storage conditions restriction considering the sensitivity of Nicorandil. It can be recommended that tablets should be stored bellow 25ºC and protected from moisture sources. From the initial target product profile it is possible to conclude that all requirements have been achieved. Table 61 presents the initial TPP and compares each parameter with the obtained drug product. Development of oral tablets containing Nicorandil Conclusions 129 Table 61. TPP of test product conclusion Parameter TPP Conclusion Dosage form and route of administration Oral tablet Pharmaceutical development achieved the production of oral tablets. Dosage design Immediate release. Dissolution results demonstrate an immediate release profile. Dosage strength 10mg Assay and content uniformity demonstrate compliance with target strenght. Assay 100% w/w label claim. Complies. (Table 59) Impurity level Known impurities: NMT 0.5% Unknown impurities: NMT 0.2% Stability has been demonstrated to be statistical similar with RP in the end of the short term stability study. Accelerated conditions revealed to be unadequate for the establishment of an expiry date due to out of specification results, although the RP exhibited the same trend. Dissolution Very fast dissolution profile (Q +5%) > 85%, 15min. Dissolution results showed that more than 85% of DS is solubilized after 15minutes. (Figure 36) Water content As low as possible. Test product exhibits higher water content that RP probably due to starch. (Table 50) Hardness (Resistance to crushing) As low as possible maintaining minimum compendial standards for oral tablet dosage form. Proposed specification is 20N – 60N 10mg tablets have been produced with adequate pharmacotechncal properties. (Table 50) Tablet shape Round, biconvex Complies Tablet dimensions 7 mm Score and embossing None Complies Colour and appearance White Complies Weight 100mg Complies (Table 50) Friability NMT 1.0% w/w Complies (Table 50) Disintegration Tablets should disintegrate in more than 20s and less than 10 min. Complies (Table 50) Development of oral tablets containing Nicorandil Conclusions 130 Development of oral tablets containing Nicorandil 131 References 1. Aulton ME. Pharmaceutics : the science of dosage form design. Edinburgh [etc.]: Churchill Livingstone; 2002. 2. Guidance for industry Q8(R2) pharmaceutical development, (2009). 3. Adeyeye MCBHG. Preformulation solid dosage form development. New York: Informa Healthcare USA; 2008. 4. Gibson M. Pharmaceutical preformulation and formulation : a practical guide from candidate drug selection to commercial dosage form. New York: Informa Healthcare; 2009. 5. Bruni G, Amici L, Berbenni V, Marini A, Orlandi A. Drug-Excipient Compatibility Studies. Search of interaction indicators. Journal of Thermal Analysis and Calorimetry. 2002;68(2):561-73. 6. Serajuddin AT, Thakur AB, Ghoshal RN, Fakes MG, Ranadive SA, Morris KR, et al. Selection of solid dosage form composition through drug-excipient compatibility testing. Journal of pharmaceutical sciences. 1999;88(7):696-704. 7. Huynh-Ba K. Handbook of stability testing in pharmaceutical development regulations, methodologies, and best practices. New York: Springer; 2009. 8. Monkhouse DC. Stability Aspects of Preformulation and Formulation of Solid Pharmaceuticals. Drug Development and Industrial Pharmacy Drug Development and Industrial Pharmacy. 1984;10(8-9):1373-412. 9. Yoshioka SSVJ. Stability of drugs and dosage forms. New York: Kluwer Academic; 2002. 10. Guidance for industry Q3B(R2) impurities in new drug products, (2006). 11. Kovaleski JKBMAGMBGCWKPRT. Impurities in generic pharmaceutical development. Advanced Drug Delivery Reviews Advanced Drug Delivery Reviews. 2007;59(1):56-63. 12. Airaksinen S KMSAWSLERJYJ. Role of water in the physical stability of solid dosage formulations. Journal of pharmaceutical sciences. 2005;94(10):2147-65. 13. Qiu YCYZGGZ. Developing solid oral dosage forms pharmaceutical theory and practice. Amsterdam; Boston; London: Academic; 2009. 14. Guidance for industry Q3A impurities in new drug substances, (2008). 15. Guidance for industry Q1C stability testing for new dosage forms, (1996). 16. Guidance for industry Q1A(R2) stability testing of new drug substances and products, (2003). 17. Baertschi SWAKMRRA. Pharmaceutical stress testing predicting drug degradation London; New York: Informa Healthcare; 2011. Available from: http://www.crcnetbase.com/isbn/9781439801802. 18. Guidance for industry Q1E evaluation of stability data, (2004). Development of oral tablets containing Nicorandil 132 19. Monkhouse DCCLV. Solid State Reactions - Theoretical and Experimental Aspects. Drug Development and Industrial Pharmacy Drug Development and Industrial Pharmacy. 1984;10(89):1175-276. 20. Bharate SSBSBBAN. Interactions and Incompatibilities of Pharmaceutical Excipients with Active Pharmaceutical Ingredients. CHIN ChemInform. 2011;42(47):no. 21. Lieberman HALL. Pharmaceutical dosage forms, tablets. New York: M. Dekker; 1980. 22. Heidemann D, Jarosz, P. J. Preformulation studies involving moisture uptake in solid dosage forms. Pharmaceutical research. 1991;8(3):292-7. 23. Hancock Bc SSLZG. Molecular mobility of amorphous pharmaceutical solids below their glass transition temperatures. Pharmaceutical research. 1995;12(6):799-806. 24. Ahlneck C, Zografi G. The molecular basis of moisture effects on the physical and chemical stability of drugs in the solid state. International Journal of Pharmaceutics. 1990;62(2–3):87-95. 25. Waltersson Jo LP. The effect of mechanical comminution on drug stability. Acta pharmaceutica Suecica. 1985;22(5):291-300. 26. Steinberg M BJFEEKKFKLAMDBTCBWML. A new approach to the safety assessment of pharmaceutical excipients. The Safety Committee of the International Pharmaceutical Excipients Council. Regulatory toxicology and pharmacology : RTP. 1996;24(2):149-54. 27. Councils IPE. http://www.ipec.org/. 28. Pifferi G, Restani P. The safety of pharmaceutical excipients. Il Farmaco. 2003;58(8):54150. 29. Bruni GBVMCGAMA. Drug-excipient compatibility studies in binary and ternary mixtures by physico-chemical techniques. Journal of Thermal Analysis and Calorimetry. 2010;102(1):193-201. 30. Guidance for industry Q9 quality risk management, (2006). 31. Yu L. Pharmaceutical Quality by Design: Product and Process Development, Understanding, and Control. Pharmaceutical Research. 2008;25(4):781-91. 32. Nagano HM, T.; Takaku, S.; Matsunaga, I.; Kujirai, T.; Ogasawara, T.; Sugano, S.; Shindo, M., inventor; Google Patents, assignee. Treating circulatory diseases1980. 33. Eeckhout E. Nicorandil: a drug for many purposes: too good to be true? European heart journal. 2003;24(14):1282-4. 34. Aizawa TO, Ken; Kato, Kazuzo. Effects of Nicorandil on Coronary Circulation in Patients with Ischemic Heart Disease: Comparison with Nitroglycerin. Journal of cardiovascular pharmacology. 1987;10:S123-S9. 35. Wagner G. Selected issues from an overview on nicorandil: tolerance, duration of action, and long-term efficacy. Journal of cardiovascular pharmacology. 1992;20 Suppl 3:S86-92. 36. Krumenacker MR, E. Clinical profile of nicorandil: an overview of its hemodynamic properties and therapeutic efficacy. Journal of cardiovascular pharmacology. 1992;20 Suppl 3:S93102. 37. Roland E. Safety profile of an anti-anginal agent with potassium channel opening activity: an overview. European heart journal. 1993;14 Suppl B:48-52. Development of oral tablets containing Nicorandil 133 38. Nakae I, Quan L, Hashimoto K, Sugimoto Y, Tsutamoto T, Kinoshita M. Mechanism of the vasodilatory action of nicorandil on coronary circulation in dogs. Cardiovascular drugs and therapy / sponsored by the International Society of Cardiovascular Pharmacotherapy. 1994;8(1):137-45. 39. Frydman A. Pharmacokinetic profile of nicorandil in humans: an overview. Journal of cardiovascular pharmacology. 1992;20 Suppl 3:S34-44. 40. Kukovetz WR, Holzmann S, Poch G. Molecular mechanism of action of nicorandil. Journal of cardiovascular pharmacology. 1992;20 Suppl 3:S1-7. 41. Bachert EL, Fung H-L. High-performance liquid chromatographic method for stability and pharmacokinetic studies of nicorandil. Journal of Chromatography B: Biomedical Sciences and Applications. 1993;619(2):336-41. 42. Nawata Y, Terao N, Terazono T, Igusa K, Yutani Y, Ochi K. Structure of N-[2- (nitrooxy)ethyl]nicotinamide (SG 75). Acta Crystallographica Section C. 1987;43(12):2460-2. 43. Sakai KNHNHUY. Nicorandil. CDR Cardiovascular Drug Reviews. 1983;1(1):227-42. 44. Nagano H, inventor; Chugai Seiyaku Kabushiki Kaisha, Tokyo, Japan, assignee. Nitric ester of N-(2-hydroxyethyl)nicotinamide and pharmaceutical use patent 4200640. 1980. 45. Veronesi AM, Veronesi PA, inventors; Google Patents, assignee. Pharmaceutical stable formulations of nicorandil2000. 46. Tipre DN, Vavia PR. Formulation optimization and stability study of transdermal therapeutic system of nicorandil. Pharmaceutical development and technology. 2002;7(3):325-32. 47. Nagai H, Kikuchi M, Nagano H, Shiba M. The Stability of Nicorandil in Aqueous Solution. I. Kinetics and Mechanism of Decomposition of N-(2-Hydroxyethyl) nicotinamide Nitrate (Ester) in Aqueous Solution. CHEMICAL & PHARMACEUTICAL BULLETIN. 1984;32(3):1063-70. 48. Eremenko LT, Nesterenko, D. A., Garanin, V. A., Kosilko, V. P. Development of improved laboratory technique for nicorandil synthesis. Russ J Appl Chem. 2009;82(10):1776-9. 49. Korolev AM, Eremenko LT, Dubikhin VV, Ol'khov YA, Charskii VV, Lodygina VP, et al. N- (2-Nitroxyethyl)nicotinamide (Nicorandil) as a monomer in quaternization polymerization. Russ Chem Bull. 2000;49(8):1487-8. 50. Korzycka L, Malgorzata K, Witczak K. The study on organic nitrates. Part I. Application of Nitrate Ion Selective Electrodes on the determination of N-(2-Nitroxyethyl)Nicotinamide. Acta poloniae pharmaceutica. 1998;55(5):349-51. 51. Iida Y, Terazono T, Sumida S, inventors; Google Patents, assignee. Jet-milled sugar organic acid; stable to pressure, humidity1989. 52. Waterman KC, Adami RC, Alsante KM, Antipas AS, Arenson DR, Carrier R, et al. Hydrolysis in pharmaceutical formulations. Pharmaceutical development and technology. 2002;7(2):113-46. 53. Carli F, Giovannone D, Saccucci G. Oral solid pharmaceutical compositions containing nicorandil for a modulated release and the process for their preparation. Google Patents; 2002. 54. WIPO. World Intellectual Property Organization http://www.wipo.int/portal/en/index.html [cited 2014]. 55. Guidance for industry analytical procedures and methods validation, chemistry, manufacturing, and controls documentation, (2000). Development of oral tablets containing Nicorandil 134 56. Guidance for industry Q2B (R1): Validation of Analytical Procedures: Text and Methodology, (1996). 57. Kaufman LRPJ. Finding groups in data : an introduction to cluster analysis. New York: Wiley; 1990. 58. Bacher JWKVM. SPSS TwoStep Cluster : a first evaluation. Nürnberg: Lehrstuhl für Soziologie; 2004. 59. Yalkowsky SH. Solubility and solubilization in aqueous media. Washington [etc.]; New York [etc.]: American Chemical Society ; Oxford University Press; 1999. 60. Chilukuri DMSGYD. Pharmaceutical product development : in vitro-in vivo correlation. New York: Informa Healthcare; 2007. 61. Guidance for Industry - Waiver of In Vivo Bioavailability and Bioequivalence Studies for Immediate-Release Solid Oral Dosage Forms Based on a Biopharmaceutics Classification System, (2000). 62. Wieland GFK. Water determination by Karl Fischer titration : theory and applications. Darmstadt: Git Verlag; 1987. 63. USP. <1174> Powder flow. 64. Food, Drug Administration HHS. International Conference on Harmonisation; guidance on Q4B Evaluation and Recommendation of Pharmacopoeial texts for use in the International Conference on Harmonisation Regions; Annex 12 on Analytical Sieving General Chapter; availability. Notice. Federal register. 2010;75(170):53873-4. 65. Gad SCWI. Pharmaceutical manufacturing handbook production and processes. Hoboken, N.J.: Wiley-Interscience; 2008. 66. Ansel HCALVPNG. Pharmaceutical dosage forms and drug delivery systems. Philadelphia, Pa.: Lippincott-Williams & Wilkins; 1999. 67. Agatonovic-Kustrin SWVRTSDTIG. Powder diffractometric assay of two polymorphic forms of ranitidine hydrochloride. International Journal of Pharmaceutics International Journal of Pharmaceutics. 1999;184(1):107-14. 68. Tiwari MCGBAK. Quantification of olanzapine polymorphs using powder X-ray diffraction technique. Journal of Pharmaceutical and Biomedical Analysis Journal of Pharmaceutical and Biomedical Analysis. 2007;43(3):865-72. 69. Society of Japanese P. The japanese pharmacopoeia : JP XIV : English version. Tokyo: Yakuji Nippo; 2001. 70. Prajapati B.G PKR. Design and in vitro evaluation of novel Nicorandil sustained release matrix tablets based on combination of hydrophilic and hydrophobic matrix system. Intl J Pharm Sci Rev Res International Journal of Pharmaceutical Sciences Review and Research. 2010;1(1):33-8. 71. Abdelbary GA, Tadros, M. I. Design and in vitro/in vivo evaluation of novel nicorandil extended release matrix tablets based on hydrophilic interpolymer complexes and a hydrophobic waxy polymer. European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik eV. 2008;69(3):1019-28. 72. Mehta TGMSG. Determination of inorganic nitrate impurity from nicorandil and its tablet dosage form by simple reversed phase liquid chromatographic method. Journal of Chromatography A Journal of Chromatography A. 2006;1101(1-2):153-7. Development of oral tablets containing Nicorandil 135 73. Ahmed A.B KNLAABKNL. Drug-excipients compatibility studies of Nicorandil in controlled release floating tablet. Int J Pharmcy Pharm Sci International Journal of Pharmacy and Pharmaceutical Sciences. 2014;6(SUPPL. 2):468-75. 74. Pahade A JVMKVJ. Formulation and development of sustained release matrix tablet of nicorandil. Intl J Pharm Sci Rev Res International Journal of Pharmaceutical Sciences Review and Research. 2010;4(1):107-11. 75. Maeda H OYIMHTTK. Formulation approach for nicorandil pulsatile release tablet. Chemical & pharmaceutical bulletin. 2008;56(4):464-7. 76. Cunningham CRKBRSLK. Formulation of Acetylsalicylic Acid Tablets for Aqueous Enteric Film Coating. PHARMACEUTICAL TECHNOLOGY. 2001;25:38-43. 77. Colorcon. Free and Bound Water in Starch 1500 compared to other excipients. http://www.colorcon.com/products-formulation/all-products/excipients/tablets/starch-1500. 78. Cunningham SLK. The Effect of STARCH 1500Æ On The Stability of Aspirin Tablets Stored Under Accelerated Conditions. In: Scientists AAoP, editor.; October 21–25, 2001; Colorado Convention Center, Denver2001. 79. Rowe RC, Sheskey PJ, Owen SC, Association AP. Handbook of pharmaceutical excipients: Pharmaceutical Press; 2006. 80. Iida Y, Sumida S, inventors; Google Patents, assignee. Method for production of stable nicorandil preparation1989. 81. Babbel M.-B FB. Fast dissolving disintegrating tablets with isomalt. Pharm Technol Eur Pharmaceutical Technology Europe. 2009;21(2):25-8. 82. Bolhuis GKEJJPEAC. Compaction properties of isomalt. European Journal of Pharmaceutics and Biopharmaceutics. 2009;72(3):621-5. 83. Ndindayino FHDKFVCRJP. Characterization and evaluation of isomalt performance in direct compression. International Journal of Pharmaceutics International Journal of Pharmaceutics. 1999;189(1):113-24. 84. Swarbrick J. Encyclopedia of Pharmaceutical Technology, Third Edition (Print): Taylor & Francis; 2006. 85. Al-Ibraheemi ZAMAMSTFSAMCITSMMAB. Deformation and Mechanical Characteristics of Compacted Binary Mixtures of Plastic (Microcrystalline Cellulose), Elastic (Sodium Starch Glycolate), and Brittle (Lactose Monohydrate) Pharmaceutical Excipients. Particulate Science and Technology Particulate Science and Technology. 2013;31(6):561-7. 86. Edge SSDFSJNCAWPM. Powder Compaction Properties of Sodium Starch Glycolate Disintegrants. Drug Dev Ind Pharm. 2002;28(8). 87. Guidance for industry dissolution testing of immediate release solid oral dosage forms, (1997). 88. Guidance for industry Q1D bracketing and matrixing designs for stability testing of new drug substances and products, (2003).