Formulation optimization of hydrogel-based contact lenses for dual-drug delivery in glaucoma treatment.

Glaucoma is a chronic ophthalmic disorder that necessitates long-term therapeutic management to prevent progressive vision loss. Conventional eye drop formulations suffer from rapid precorneal drug elimination, leading to poor bioavailability and frequent dosing requirements. In this study, hydrogel-based contact lenses were developed and optimized for the sustained dual-drug delivery of Timolol Maleate and Brimonidine Tartrate, two first-line antiglaucoma agents. The formulation was optimized using Box-Behnken Design (BBD), where the effects of HEMA concentration (85- 95%), EGDMA crosslinker concentration (0.5-1.5%), drug loading (2-6 mg/mL), and water content (30-50%) were evaluated on key parameters such as swelling ratio, tensile strength, optical transparency, drug release kinetics, and drug retention. The optimized formulation exhibited a swelling ratio of 169.1%, tensile strength of 1.2 MPa, and over 95% transparency, ensuring structural integrity and visual clarity. FTIR and DSC confirmed the compatibility of the drug- polymer system, with no significant chemical interactions observed. In vitro swelling studies demonstrated that higher HEMA content promoted hydration, while increased EGDMA crosslinking reduced water uptake, thereby modulating drug diffusion. The cumulative in vitro drug release study revealed a sustained release profile, with Timolol Maleate and Brimonidine Tartrate achieving 96.25% and 97.42% release, respectively, within 24 hours. Drug release followed First- order, Higuchi, and Korsmeyer-Peppas models, indicating diffusion-controlled, non-Fickian kinetics. This suggests hydrogel-based contact lenses provide sustained drug delivery, reducing dosing frequency and improving compliance in glaucoma therapy compared to conventional eye drops.