| Abstract: | New ophthalmic drug delivery systems are curently receiving increased attention, in part because of the expected emergence of new drugs with short biological half-lives whose usefulness may depend on a more continuous drug supply than eyedrops can provide, but also because of the potential of some delivery systems to reduce the side effects of the more potent drugs recently introduced or presently under investigation. Some ophthalmic delivery systems extend the duration of drug action by enhancement of corneal absorption; these systems include soluble gels and emulsions, hydrophilic ocular inserts, ion-pair associations, prodrugs, and liposomes. Since these systems enhance the “pulse entry” of the drug, they are limited to use with drugs whose dose-related side effects are not serious. Other delivery systems provide for a controlled release of drugs and therefore minimize the pulse entry with which side effects are associated. They can be based on any of several different mechanisms and include both erodible and nonerodible matrices. The various delivery systems that have recently been developed and those that are currently known to be under investigation are described in this paper, along with some observations regarding the future outlook of ophthalmic drug delivery systems. |
