Extended delivery of hydrophilic drugs from silicone-hydrogel contact lenses containing vitamin E diffusion barriers.

This paper proposes an approach for increasing drug release durations from contact lenses and other biomedical devices by in situ creation of transport barriers of Vitamin E that force drug molecules to diffuse through long tortuous path. Results show that the increase in release duration is quadratic in Vitamin E loading, which is consistent with proposed mathematical models. Loadings of 10 and 40% Vitamin E increase release time of timolol by a factor of about 5 and 400, respectively for NIGHT&DAY lens. Similar results have been obtained for other hydrophilic drugs including fluconazole and dexamethasone 21-disodium phosphate (DXP). Vitamin E loading in the NIGHT&DAY lens leads to slight increase in lens sizes (6.5% increase for 30% loading), a slight reduction in oxygen diffusion (about 40% reduction for 75% loading), and a more significant reduction in the ion permeability (50% reduction for 10% loading). Additionally, Vitamin E loading has a beneficial effect of blocking UV radiation which will reduce the corneal damage due to UV light. Copyright 2010 Elsevier Ltd. All rights reserved.