Zero‐Order Antibiotic Release from Multilayer Contact Lenses: Nonuniform Drug and Diffusivity Distributions Produce Constant‐Rate Drug Delivery

A novel approach to zero‐order constant‐rate drug delivery from contact lenses is presented. Quasi‐Case II non‐Fickian transport is achieved by nonuniform drug and diffusivity distributions within three‐layer bimodal amphiphilic conetworks (β‐APCNs). The center layer is a highly oxygen permeable β‐APCN matrix, which contains the drug and exhibits a high drug diffusivity. The outer β‐APCN layers contain no‐drug and are loaded with vitamin E, which slows diffusion. In contrast to single‐layer neat‐polymer and vitamin E‐loaded films that display first‐order “burst” kinetics, it is demonstrated experimentally and by modeling that the combined effect of nonuniform distribution of drug loading and diffusion constants within the three‐layer lens maintains low local drug concentration at the lens–fluid interface and yields zero‐order drug delivery. The release rates of topical antibiotics provide constant‐rate therapeutic‐level delivery with appropriate oxygen permeability for at least 30 h, at which time ≈25% of the drug was released.