Extended release of dexamethasone from silicone-hydrogel contact lenses containing vitamin E

Ophthalmic drug delivery by contact lenses is expected to be more efficient due to continuous extended release of drug and increased residence time in the tear film. However, commercial contact lenses release ophthalmic drugs for a short period of about an hour and are thus not suitable for extended delivery use. Here we explore a novel approach of increasing the release duration of dexamethasone (DX) from commercial contact lenses by loading Vitamin E into the lenses. The Vitamin E was loaded into the lenses by soaking the lenses in Vitamin E-ethanol solution followed by ethanol removal through evaporation. The results show that with about 30% of Vitamin E loading in the contact lens, the DX release time can be increased to 7 to 9 days for ACUVUE (R) OASYS (TM), NIGHT & DAY (TM), and O(2)OPTIX (TM), which is a 9 to 16 fold increase compared to the DX release duration by pure contact lens without Vitamin E loading. The DX delivery by contact lens can be viewed as a one-dimensional transport by a flat thin film, and a mathematical model based on the drug diffusivity difference between Vitamin E and silicone hydrogel was also proposed to explain the DX release time increase by Vitamin E loaded contact lens. (C) 2010 Elsevier B.V. All rights reserved.