Pathology of eye, especially in the case of
glaucoma, requires optimal therapeutically effective concentration of the
drug in the ocular tissues for prolonged period of time with decreased dosing frequency and improved patient compliance. In the present study,
brimonidine tartrate (BRT) ocular inserts were designed based on hydrophilic and/or inert/zwitterionic
polymer matrix to design mucoadhesive and extended release ocular inserts. Designed inserts were evaluated for their physicochemical properties such as crushing strength/hardness, friability,
drug content and mucoadhesion, and erosion and in vitro drug release characteristics. The selected optimised formulations were compared with marketed preparation for in vivo ocular irritation in healthy rabbits and for in vivo pharmacodynamic efficacy on
alpha-chymotrypsin-induced glaucomatous rabbits. The developed formulations showed good physicochemical properties and mucoadhesive strength, and a good correlation was seen between rate of erosion or swelling with drug release rate in case of formulations with higher proportion of
polyethylene oxide (PEO). Modulation of drug release was achieved by incorporating
Eudragit in PEO matrix. Addition of
Eudragit resulted in shifting of drug release mechanism from erosion-controlled to diffusion-controlled mechanism. In vivo ocular irritation studies confirmed the absence of any irritation upon administration in rabbits. Intraocular pressure (IOP) measurement studies showed an improved IOP-lowering ability of ocular insert of BRT in comparison to
eye drops.