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Abstract: Currently, approximately 100 million people are estimated to be wearing contact lenses, and the number is increasing exponentially. Although the main use of contact lenses is for correcting ametropia problems, they also hold interest as therapeutic devices for the relief of ocular pain, promotion of corneal healing, mechanical protection and support, maintenance of corneal epithelial hydration, and drug delivery. Ocular drug administration is particularly challenging and recent research has been directed towards the design of novel drug delivery systems capable of prolonging the permanence of the drug in the precorneal area and, thus, potentially increasing bioavailability and minimizing adverse effects. Conventional hydrogel soft contact lenses have the ability to absorb some drugs and release them into the post-lens lacrimal fluid, minimizing clearance and sorption through the conjunctiva. Their ability to be a drug reservoir strongly depends on the water content and thickness of the lens, the molecular weight of the drug, the concentration of the drug loading solution and the time the lens remains in it. However, the ability of contact lenses to load drugs and to control their release is in general inadequate and the following approaches, based on modifications of the polymer network, are currently under evaluation: (i) covalent binding of the drug to the lens network via labile bonds; (ii) inclusion of the drug in colloidal structures that are dispersed in the lens and are responsible for controlling drug release; (iii) functionalization of the network with chemical groups that work as ion-exchange resins; and (iv) creation in the lens structure of imprinted pockets that memorize the spatial features and bonding preferences of the drug and provide the lens with a high affinity and selectivity for a given drug. In this review, the possibilities and the advantages/drawbacks of these new types of contact lenses as drug delivery systems are critically analyzed. ® 2006 Adis Data Information BV. All rights reserved
Template and target information: Review - drug eluting contact lenses