Effect of pentoxifylline in treatment of induced ocular hypertension in rabbits

 Corresponding author: Baha'a A Abdul-Hussein Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution License 4.0. Effect of pentoxifylline in treatment of induced ocular hypertension in rabbits Baha'a Ameen Abdul-Hussein 1, * and Hassanen Abbas Radi 2 1 Department of Pharmacology, College of Medicine, University of Al - Nahrain, Baghdad - Iraq. 2 Ophthalmology consultant, Al-Diwaniya Teaching Hospital. AlDiwaniya – Iraq. World Journal of Biology Pharmacy and Health Sciences, 2025, 22(01), 282-288 Publication history: Received on 19 February 2025; revised on 08 April 2025; accepted on 12 April 2025 Article DOI: https://doi.org/10.30574/wjbphs.2025.22.1.0348 Abstract In glaucoma, as optic neuropathy gradually proceeds unnoticed by the patient, early detection and treatment is of paramount importance in arresting or controlling the progress of damage. To explore effects of topical pentoxifylline on intraocular pressure (IOP) ocular hypertensive eyes of rabbits. A group of 36 males of the rabbits were included in this study. Induction of ocular hypertension was achieved by injection of hydroxy propyl methylcellulose in the anterior chamber of rabbits right eye. The present study was designed to evaluate the possible beneficial therapeutic effect. The included rabbits were divided into distilled water group, timolol (0.25% and 0.5%) groups, and pentoxifylline (0.25% and 0.5%). Each of drug eye drops (including distilled water) were instilled into right eyes 3 times/day for 10 days therapeutically. The rabbits had been examined for the IOP, pupil diameter, light reflex, corneal reflex, and conjunctival redness prior to instillation of drugs and along the trial period. Results: Ocular hypotensive effects of pentoxifylline (0.25%) and (0.5%) eye drops were more efficient than that of distilled water (P<0.01). Furthermore, pentoxifylline eye drop was effective like timolol eye drop (P>0.05) in its ocular hypotensive effect in both concentrations along the trial period. In both parts of the present study and regarding each of mean pupil diameter, light reflex, corneal reflex and conjunctival redness, pentoxifylline (0.25% or 0.5%) eye drops had no significant adverse effect (P > 0.05). Conclusions: Pentoxifylline eye drops instilled 3 times / day had an obvious beneficial, safe, and tolerable therapeutic ocular hypotensive effects on hydroxy propyl methyl cellulose - induced ocular hypertension in rabbits. Keywords: Pentoxifylline; Timolol; Intraocular Pressure; Aqueous humor; Glaucoma 1. Introduction Primary glaucoma which are marked by an increase of intraocular pressure (IOP) are of two main types: primary open angle glaucoma and primary angle closure glaucoma; when optic nerve damage has occurred despite a normal IOP, this is called normal tension glaucoma. Secondary glaucoma refers to any case in which another disease causes or contributes to increase eye pressure, resulting in optic nerve damage and vision loss 1. In glaucoma, as damage gradually proceeds unnoticed by the patient, early detection and treatment is of paramount importance in arresting or controlling the progress of damage. In recent years, progress in the diagnosis and treatment World Journal of Biology Pharmacy and Health Sciences, 2025, 22(01), 282-288 283 of glaucoma has been remarkable, with numerous new diagnostic and therapeutic aids being introduced in the clinical setting, and the diagnosis and treatment of the disease has become multi-faceted 2. Medical treatment of glaucoma includes topical β adrenergic antagonists(timolol, levobunolol, carteolol, metipranolol, and betaxolol) 3, topical sympathomimetics (dipivefrin, apraclonidine, and brimonidine) 4, topical cholinergic agonists (pilocarpine, carbachol and ecothiophate iodide) 5, topical carbonic anhydrase inhibitors (dorzolamide and brinzolamid), carbonic anhydrase inhibitors (acetazolamide and methazolamide) 3, topical prostaglandin analogs (latanoprost, travoprost, bimatoprost and unprostone) 5, and osmotic agents (mannitol and glycerin) 6. Pentoxifylline is a xanthine derivative, is widely promoted for use in this condition but is not recommended. It is thought to act by reducing the viscosity of blood and perhaps increasing the deformability of red blood cells, allowing blood to flow more easily through partially obstructed areas5,6. Aim of the study This study was designed in order to: • evaluate the possible therapeutic hypotensive effects of topically applied pentoxifylline on mean IOP values of experimentally induced ocular hypertensive eyes of rabbits. • explore the possible local adverse effects of the tested drug in an attempt to assess its safety. 2. Material and methods The used materials in the present study are listed below with their sources accordingly: Table 1 Materials that used in experiment Materials Source Benzalkonium chloride SDI (supplier) Pentoxifylline tablets (40 mg) SanofiCo. France. Distillator Gesellschaft fur Labortech, Nikm. b.h. and Co., type 2016Germany Hdroxypropyl methyl cellulose ophthalmic solution (2%) (United states pharmacopoeia) Focus vision care Ketamine hydrochloride(50 mg/ml) HOLDEN MEDICALLelystad the Netherlands Lidocaine hydrochloride (2%) Solution Avenzor –Syria pH. Meter Friederg/Hessen-Germany Pupil gauge Al-Zahrawi Private Hospital Sartorius balance Werke–GMBH, type 2842Germany Schiotz tonometer Eichtabelle – Germany Timolol Pharmacia Co.- France 2.1. Animal and Housing A group of 36 adult male of New Zealand rabbits (Oryctologus cuniculus), aged near one year with body weight ranged 1.5-2 kg were included in the study. Animals were kept on fresh trefoil diet, water ad libitum, suitable temperature and normal light. 2.2. Induction of ocular hypertension in rabbits Rabbits had been injected with hydroxpropyl methylcellulose (0.4 ml) of (2% w/v) after proper anesthetization by intramuscular administration of 1ml ketamine hydrochloride. The injection of hydroxpropyl methylcellulose is done by use (27 G *1/2) needle which introduced into anterior chamber and inject 0.4 ml of (2% w/v) hydroxypropyl methyl World Journal of Biology Pharmacy and Health Sciences, 2025, 22(01), 282-288 284 cellulose to right eye and the left as control , the injection was under sterile condition, and the animals kept in normal light room and suitable temperature and monitored. After 48 hours the IOP increased to (20.123.8 mmHg) and this elevating could persist for 10 days, after that, the IOP start to decrease gradually. The type of induced glaucoma is open angle glaucoma 10, 11, 12. 2.3. Preparation of pentoxifylline (0.25%, 0.5 %) eye drops 13 Table 2 Materials of pentoxifylline eye drop preparation Pentoxifylline 0.25g, 0.5 g Benzalkonium chloride (1% ) (w / v) 1 ml Phosphate buffer to 100 ml 2.4. Treatment groups In the present study, the drugs were administered only to the right eyes of the rabbits whereas the left eyes were administered distilled water. To evaluate the possible therapeutic hypotensive effects In this study, the drugs (including distilled water) were administered topically 3 times/day to the right eyes of rabbits only after the ocular hypertension was definitely established, whereas the left eyes received only distilled water. This part of study was furthermore divided into two subdivisions: 2.4.1. Tested agents at (0.25%) concentrations (6 rabbits / group) • Distilled water (Negative control) group (i.e., Distilled water was administered to both eyes of rabbits). • Timolol (0.25%) (Positive control) group. • Pentoxifylline (0.25%) (Tested drug) group. 2.4.2. Tested agents at (0.5%) concentrations (6 rabbits / group): • Distilled water (Negative control) group (i.e., Distilled water was administered to both eyes of rabbits). • Timolol (0.5%) (Positive control) group. • Pentoxifylline (0.5%) (Tested drug) group. 2.5. Tested Parameters The animals had been examined for the IOP, pupil diameter, light reflex, corneal reflex, and conjunctival redness14 prior to instillation of drugs and then daily after drugs instillation along the trial period. 2.6. Statistical methods In this study, the obtained quantitative data were presented as (mean ± S.E.M.) (Standard error of mean). Student paired t-test was used for assessing the effectiveness of employed therapy for the right eyes of rabbits in a given group. While student (unpaired) t-test for independent data was used to test the significance of the difference between the results of right and left eyes of rabbits in a given group or between the results of the right eyes of rabbits of (any two groups). The differences were accepted as significant if the calculated value for (t) was equal or greater than its tabulated value at (0.05) level of (P) (i.e. 0.01 < P ≤ 0.05) and highly significant if (P ≤ 0.01). Chi-square (X 2) test was used whenever it was applicable (i.e. for independent qualitative data). The differences were accepted as significant if (0.01 < P ≤ 0.05) and highly significant if (P ≤ 0.01) 15, 16. World Journal of Biology Pharmacy and Health Sciences, 2025, 22(01), 282-288 285 3. Results 3.1. Pentoxifylline (0.25%) group Post induction of ocular hypertension the IOP of right eyes was (25.63±0.004 mmHg). Treatment with pentoxifylline (0.25%) eye drop (3 times/day) caused a highly significant decrease in mean IOP from (23.32 ±0.06 mm Hg) to reach (19.01± 0.022 mmHg) within 5 days (P<0.01); such decline continued like so for further 5 days of treatment to reach (13.02±0.001 mmHg) by the end of trial period (Figure 1). Along the trial period, the ocular hypotensive effect of pentoxifylline (0.25%) eye drop was more efficient than that of distilled water (P<0.01) but was similar to timolol (0.25%) eye drop (P > 0.05) (Table 3). Regarding each of mean pupil diameter, light reflex, corneal reflex and conjunctival redness, pentoxifylline (0.25%) eye drops had no significant effect (P > 0.05) on them at any time during the trial period. HS = Highly significant difference (P ≤ 0.01),* =Compared to corresponding mean IOP values at left eyes, $ = Compared to corresponding mean IOP values of right eyes at first day post induction of ocular hypertension. Figure 1 Effect of Pentoxifylline (0.25%) eye drops instilled 3 times daily on mean IOP values of rabbit's right eyes (n = 6) with induced ocular hypertension World Journal of Biology Pharmacy and Health Sciences, 2025, 22(01), 282-288 286 Table 3 Significance of differences between pentoxifylline (0.25%) and each of timolol (0.25%) and distilled water groups regarding the response of IOP of right eyes of rabbits Post induction of ocular hypertension Pre induction Group Post treatment (Day) Pretreatment 10th 5th 1st HS (P) HS (P) HS (P) NS NS Distilled Water NS NS NS NS NS Timolol NS = No significant difference (P>0.05),; HS = Highly significant difference (P  0.01), ; (P) = The lowest value of mean IOP belongs to pentoxifylline group. 3.2. Pentoxifylline (0.5%) group Post induction of ocular hypertension, the mean IOP of right eyes was (25.5±0.002mmHg). Treatment with pentoxifylline (0.5%) eye drop (3 times/day) highly significant decreased the IOP from (23.01 ± 0.17 mmHg) to reach (17.1 ± 0.01 mmHg) within 5 days (P<0.01); such decline continued like so for further 5 days of treatment to reach ( 12.01± 0.03 mmHg), by the end of trial period (Figure 2). During trial period, pentoxifylline (0.5%) eye drop was more efficient than distilled water in its ocular hypotensive effect along the trial period (P<0.01) but was similar to timolol (0.5%) eye drop (P>0.01) (Table 4). Compared to distilled water group, pentoxifylline (0.5%) eye drop had no significant effect (P > 0.05) on each of pupil diameter, light reflex, corneal reflex and conjunctival redness at any time during the trial period. * =Compared to corresponding mean IOP values at left eyes, $ = Compared to corresponding mean IOP values of right eyes at first day post induction of ocular hypertension. Figure 2 Effect of Pentoxifylline (0.5%) eye drops instilled 3 times daily on mean IOP values of rabbit's right eyes (n = 6) with induced ocular hypertension. NS = No significant difference (P>0.05), HS = Highly significant difference (P ≤ 0.01) World Journal of Biology Pharmacy and Health Sciences, 2025, 22(01), 282-288 287 Table 4 Significance of differences between pentoxifylline (0.5%) and each of distilled water and timolol (0.5%) groups regarding the response of IOP of right eyes of rabbits Post induction of ocular hypertension Pre induction Group Post treatment (Day) Pretreatment 10th 5th 1st HS (P) HS (P) HS (P) NS NS Distilled Water NS NS NS NS NS Timolol NS = No significant difference (P>0.05),; HS = Highly significant difference (P  0.01), ; (P) = The lowest value of mean IOP belongs to pentoxifylline group. 4. Discussion The results of this study, had documented the beneficial therapeutic role of pentoxifylline eye drops at its two tested doses (0.5% and 0.25%) when instilled 3 times/ day for 10 days since each of these concentrations could highly significant (P < 0.01) reduced the mean IOP along the trial period in a pattern that was more efficient (P < 0.01) than that of distilled water. And was noticeable that pentoxifylline caused ocular hypotensive effect similar to that of timolol. The results and the expected effect of pentoxifylline appeared to be in accordance to what was documented by Santana et al., (2006) 17 who reported that pentoxifylline potent ocular hypotensive effect. In agreement to what was found by Giuliano et al., (2001) 18, the present study and along the trial period, there was no effect on mean IOP in the contra lateral eye after its topical administration in both ocular normotensive and hypertensive rabbits; this probably indicated that topically applied pentoxifylline exerted its ocular effect locally and not systemically. However, these results conflicted with those of Santana et al., (2006) 17 who found the IOP reduction in untreated eye after unilateral topical application of pentoxifylline in rabbits. Pentoxifylline act by reducing the viscosity of blood and perhaps increasing the deformability of red blood cells, allowing blood to flow more easily through partially obstructed areas. So it may act by same mechanism to decrease IOP by facilitate aqueous humor drainage. In the present study, when being compared to results of distilled water, pentoxifylline eye drops seemed to be quite tolerable since there was no significant difference (p>0.05) between their effects on each of mean pupil diameter, light reflex, corneal reflex and conjunctival redness. 5. Conclusion Each of pentoxifylline (0.25%) or (0.5%) eye drops instilled 3 times / day had a beneficial, safe, and tolerable ocular hypotensive effects on hydroxy propyl methyl cellulose - induced ocular hypertension in rabbits. Compliance with ethical standards Disclosure of conflict of interest No conflict of interest to be disclosed. Statement of ethical approval This study was performed under ethics of researches , and humane treatment of animals References [1] Glaucoma Research Foundation. www.Glaucoma.Org. (20013). (Cited:8.Fab. 2013). 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