Polymer Based Drug Delivery:Magnetically Modulated and Bioerodible Systems

Abstract

Polymer based drug, delivery systems have been considered for many applications to supplement standard means of medical therapeutics. Currently nitroglycerin, scopolamine, progesterone, and pilocarpine [1] are being administered on a chronic basis from such devices. These delivery systems are less complex than mechanical pumps and smaller because drug can be stored as a dry powder within the polymer matrix. Recent advances have shown that polymeric devices may be utilized for very large molecular weight drugs [2], for drugs that must be delivered in minute quantities [3], and at zero order kinetics [4]. None-the-less two very important problems remain to be answered. First, virtually all of these systems display rates of release that decay with time or are at the very best a constant function of time. None of them allows for control of drug release once the device has been implanted and release intiated. Second, after implantation and depletion of incorporated drug, these systems must be removed, as they are for the most part not biodegradable. Those polymers that have been proposed for biodegradable drug delivery systems generally progessively loosen because erosion is from the entire matrix bulk instead of just the surface. The result is that neither the rate of drug release nor polymer biodegradation is constant or predictable. This paper discusses ongoing research in our laboratory in these two areas.