In vitro characterization of a controlled-release ocular insert for delivery of brimonidine tartrate

Glaucoma is the second leading cause of blindness in the US. Brimonidine tartrate (BT) is a modern anti-glaucoma agent that is currently administered as frequently as a thrice-daily topical eye drop medication. Accordingly, compliance with BT regimens is low, limiting overall effectiveness. One attempt that has previously proved effective in addressing non-adherence is the formation of ocular inserts, such as the Ocusert(®), whose diffusion-based control released an older drug (pilocarpine) for a week-long period. Modern controlled drug-release technology provides an avenue for extending the release of practically any drug (including new drugs such as BT) for as long as 1 month from a singular insert. Currently, no controlled-release formulations for BT exist. This work outlines the development and characterization of a BT-releasing ocular insert designed from poly(lactic co-glycolic) acid/polyethylene glycol (PEG). It was found that a formulation containing 15% PEG can be created that produces a linear BT-release profile corresponding to BT eye drop delivery estimates. Additionally, these inserts were shown, through the use of atomic force microscopy and scanning electron microscopy, to have smooth surfaces and physical properties suitable for ophthalmic use.