Formulation and release of timolol maleate from ocusert based on gelatin-N-(3-dimethylaminopropyl)-N-ethylcarbodiimide polymer

Abstract

Context: Glaucoma is a disease of the eyes characterized by an increase in the intraocular pressure. Timolol maleate is commonly used as eye drops for chronic glaucoma treatment. Aims: To formulate an ocusert (novel ophthalmic drug delivery systems) in order to overcome disadvantages of eye drops such as patient’s noncompliance and drainage of the administered solution. Also, to improve treatment outcomes by keeping sustained release of constant amount of timolol maleate and to avoid repeated administration of conventional eye drops. Methods: Timolol maleate ocuserts were formulated using cross-linked gelatin polymer which was prepared using N-(3-dimethylaminopropyl)N-ethylcarbodiimide (EDC) and N-hydroxysuccinamide (NHS). Different ocusert formulas were prepared (M1-M17) by varying concentrations of EDC, different temperatures and time for the cross linking as per central composite design. Physicochemical characteristics of drug loaded ocuserts were investigated. Results: Selected formula (M8) exhibited an excellent in vitro drug release results which was extensively evaluated. Fourier transform infrared spectral scan indicates no incompatibility exists between the drug and the polymer used. M8 formula was evaluated in vivo by assessing the eye irritancy, drug release and therapeutic effect when placed in the cul-de-sac of rabbit’s eyes and was compared with conventional eye drops therapy. Conclusions: There was a correlation between in vivo and in vitro release of timolol maleate which is associated with a decrease of glaucoma induced by dexamethasone eye drops in experimental rabbits. The data established the potential of ocusert to improve the therapeutic delivery of timolol maleate and offers a promising option in glaucoma treatment.