the invention provides elastomeric copolyester amides , elastomeric copolyester urethanes , and methods for making the same . the polymers are based on α - amino acids and possess physical , chemical and biodegradation properties that render them suitable for use in the human body . the polymers are useful as carriers of drugs or other bioactive substances . the polymers can also be linked , intermixed , or a combination thereof , to one or more drugs . additionally , the polymers can be used to coat stents , for example , to suppress restenosis . furthermore , the biodegradation of the copolyester amides and copolyester urethanes allows for the delivery of essential α - amino acids to sites in the body , for example , to facilitate wound repair of injured tissues .