Ophthalmic delivery of Cyclosporine A from Brij-97 microemulsion and surfactant-laden p-HEMA hydrogels.

Cyclosporine A (CyA) is an immunosuppressant drug that is used for treating a variety of ocular diseases and disorders. CyA is commonly delivered via eye drops, which is highly inefficient due to a low bioavailability of less than 5%. The bioavailability of ophthalmic drugs can be substantially improved to about 50% by delivering them via contact lenses. This paper focuses on the development of nanostructured poly (2-hydroxyethyl methacrylate) (p-HEMA) hydrogels containing microemulsions or micelles of Brij 97 (C(18)H(35)(OCH(2)CH(2))(10)) for extended delivery of CyA. Release of CyA from these nanostructured hydrogels was performed in vitro to explore the mechanisms of release and the effects of surfactant concentration, processing conditions and storage on the release kinetics. Results show that the surfactant and microemulsion-laden gels can deliver CyA at therapeutic dosages for a period of about 20 days. Release of the drug is diffusion controlled with effective diffusivities decreasing with increasing surfactant loading. The release kinetics are relatively similar for both surfactant and microemulsion-laden gels with comparable surfactant loading. The results also show that these hydrogels retain their effectiveness even after exposure to all the relevant processing conditions including unreacted monomer extraction, autoclaving and packaging, and so these materials seem to be very promising for ophthalmic delivery of CyA and perhaps other drugs.