Design and characterization of PH responsiveopthalmic in-situ gel of Brimonidine Tartrate

Abstract

Glaucoma is a progressive ocular disorder characterized by elevated intraocular pressure (IOP), leading to irreversible optic nerve damage and vision loss if left untreated. Conventional ophthalmic eye drops exhibit poor ocular bioavailability due to rapid precorneal elimination, tear turnover, and nasolacrimal drainage, resulting in frequent dosing and reduced patient compliance. The present study aimed to formulate and evaluate a pH-triggered ophthalmic in-situ gel of Brimonidine Tartrate using Carbopol 980 and HPMC K100M to improve precorneal residence time and sustain drug release. Preliminary optimization studies were carried out to select suitable concentrations of Carbopol 980 and HPMC K100M. A total of nine formulations (F1–F9) were prepared using a 3² factorial design and evaluated for physicochemical properties, including pH, viscosity, gelling time, gelling capacity, gel stability, drug content, in-vitro drug release, sterility, and stability. The prepared formulations showed acceptable clarity, homogeneity, and pH suitable for ocular administration. Rheological studies demonstrated pseudoplasticbehavior with viscosity increasing after gelation. The optimized formulation (F5) exhibited optimum viscosity, rapid gelation (4.76 s), satisfactory gel stability (>8 h), drug content of 100.37%, and sustained drug release of 52.12% over 12 h. Sterility testing confirmed the absence of microbial growth, while stability studies indicated no significant changes in physicochemical properties during storage. The developed Brimonidine Tartrate ophthalmic in-situ gel demonstrated sustained drug release, prolonged ocular residence, and improved formulation stability, suggesting its potential as an effective alternative to conventional ophthalmic eye drops for glaucoma management.