Recent developments in drug delivery.

Some recent innovative approaches to drug delivery have demonstrated that the administration of drugs can be more rigidly controlled with respect to the rate and amount of drug delivered to sites of action than from the conventional dosage forms. One category of controlled release referred to as programmed drug delivery primarily involves the application of polymers of defined specifications to release agents from either non-bioerodible membrane-controlled systems or bioerodible and non-bioerodible matrices. Also included here are the pro-drugs, inactive derivatives of drugs which are transformed into the active form in vivo but possess improved solubility, stability and disposition properties, yielding more efficient action and fewer side effects. Thus, exploitation of several routes of administration have resulted in products which are inserted ophtalmically, rectally or vaginally, implanted subcutaneously, taken orally or applied topically to achieve transdermal delivery of drugs to the systemic circulation. In several cases, release is designed to follow zero-order kinetics to achieve control of therapeutic plasma concentrations for prolonged time periods. Targeting of drugs by carrier is another form of controlled release technology. Normally administered intravenously, carriers such as liposomes, nanoparticles, microspheres, human cells and linear macromolecules are finding application in treating disease states with drugs which previously were unavailable to treatment.