Effect of ophthalmic preparation of methyldopa on induced ocular hypertension in rabbits

Glaucoma is a type of ocular disorder with multifaceted etiologies characterized by progressive optic nerve damage and ultimately loss of visual field. This study aimed to evaluate the possible intraocular pressure (IOP) lowering effect of an ophthalmic preparation of methyldopa (MD) in corticosteroid-induced ocular hypertension in rabbits. Forty New Zealand white male rabbits were assigned to the experiment and then randomly divided into five groups (n = 8). Ocular hypertension was induced by weekly subconjunctival injection of betamethasone suspension in both eyes. Animal groups included the control (healthy) group, which received the ophthalmic vehicle only; the standard (timolol) group, which received 0.5% timolol eye drops (ED); and the MD groups, which received 0.5%, 1%, and 2% of methyldopa ophthalmic preparation. Treatments were applied to the right eye twice daily for 7 days, whereas the left eye served as a control and was given only distilled water. IOP was recorded and ocular reflexes were observed. Weekly subconjunctival injections of betamethasone resulted in a significant elevation in the IOP (P ≤ 0.001) that was reduced after treatments with timolol 0.5% and MD at different concentrations. Timolol showed the highest reduction (P ≤ 0.001) in the mean IOP with a 30% reduction. MD showed a concentration-dependent reduction with the highest reduction (P ≤ 0.01) observed at 2% compared to the induced/distilled water (DW) eyes and no significant difference compared to the timolol 0.5% (P ≥ 0.05) with a 24.2% reduction in the mean IOP. Methyldopa managed to reduce the IOP in the chronic model of glaucoma, making MD a promising addition to the anti-glaucoma medications.