new biodegradable polyanhydrides are disclosed , which are prepared by homopolymerization of dimer of bile acid , especially lithocholic acid , or bycopolymerization with linear dicarboxylic acid , especially sebacic acid . these biodegradable polyanhydrides have degradation kinetics and a release rate that make them particularly useful for controlled drug release . more specifically , the degradation kinetics of such anhydrides and the release rate of molecules embedded therein make them useful as matrices for controlled drug release systems . the rates of degradation and release can be adjusted by the copolymer composition . the near zero - order kinetrics of release of the drug embedded in the matrices made of such anhydrides , make the same particularly useful since they can deliver an active ingredient at a constant rate for long period of time , avoiding the inauspicious saw - tooth pattern of conventional systemic administration .