biodegradable controlled release systems providing prolonged controlled release of drugs , and methods for the manufacture thereof are disclosed . the systems are formed from a biocompatible , biodegradable polymer , in particular poly - 4 - hydroxybutyrate or copolymers thereof . copolymers of 4 - hydroxybutyrate include but are not limited to poly - 3 - hydroxybutyrate - co - 4 - hydroxybutyrate , and poly - 4 - hydoxybutyrate - co - glycolate . drugs are generally incorporated into the polymer using a method that yields a uniform dispersion . the type of drug and the quantity are selected based on the known pharmaceutical properties of these compounds . the systems may be administered for example by implantation , injection , topical administration , or oral ingestion . they may also be used in combination with a medical device , for example , a stent . a major advantage of the drug delivery system is that it does not need to be removed after use since it is slowly degraded and cleared by the patient &# 39 ; s body . the device has desirable physical properties , including strength , modulus and elongation .