Development of a Topical Polymeric Mucoadhesive Ocular Delivery System for Azithromycin

Purpose: Azithromycin is an azalide class of antibiotic with pharmacodynamics that have made it a valuable agent in the treatment of soft tissue infections. In ophthalmology, oral administration of azithromycin has been proven effective for the treatment of trachoma. However, topical formulations of azithromycin to treat ocular surface infections have been challenging to develop because of the drug's hydrophobicity and instability in aqueous solutions at pH levels that are comfortable in the eye. The design of a polycarbophil polymer-based delivery system for a topical formulation of azithromycin was evaluated for its ability to provide drug stability, comfort, and increased retention of the formulation in the eye. Methods: Formulations of 0.5% and 1.0% azithromycin were created in polycarbophil, a lightly cross-linked polyacrylic acid polymer that was adjusted to a viscosity, pH, and osmolality that are suitable for dispensing in the eye. Results: The polycarbophil-based ophthalmic delivery system, DuraSite (InSite Vision, Alameda, CA), helps solubilize azithromycin and retard its degradation in aqueous solution. The formulation was stable at room temperature as well as 5 degrees C. Upon administration of a single drop of 1% azithromycin in DuraSite ophthalmic solution in rabbits' eyes, tear concentrations of azithromycin ranged from 87 to 288 mu g/g and high concentrations were sustained for over a 24-h period. Conclusions: Azithromycin can be developed as an eyedrop in an aqueous ocular delivery system for the treatment of ocular surface infections. The ocular delivery system, DuraSite solubilizes azithromycin at a high concentration in an aqueous solution and protects it from degradation during manufacture and storage. The development of azithromycin in this delivery system enhances the antibiotic's usefulness in ophthalmology for the topical treatment of ocular surface bacterial infections and lid margin diseases.