Bioerodible implants with programmable drug release

Taking advantage of polymer surface erosion a polymer matrix was developed that allows to release either one drug in two phases or two drugs one after another. The first period of drug release from these implants lasts between one and two weeks and is followed by a second period of similar duration. The matrices consist of several layers of surface eroding polymer. As these polymers erode in general fast, it was necessary to incorporate also bulk eroding polymers to obtain implants with the desired release characteristics and yet keep the dimensions of the implant small. The polymers used for the manufacture are p(CPP-SA) 20:80, a polyanhydride, and poly(D,L-lactic acid). Both are biocompatible and have been used for the manufacture of FDA-approved devices before. Theoretical erosion models were used to support the design of implants as well as to investigate some of the problems involved with drug release.