Abstract

PIP: Biodegradable or erodible delivery systems are represented by contraceptive devices where the matrix also dissolves and both the drug and the system's components reach systemic circulation. One promising feature of such a system is the possibility of achieving programmed release whereby the active component is made available only during specified periods. A major drawback of the system is that if the device were made of microparticles, the occurence of a serious adverse reaction can be counteracted only by administration of other active principles, and not by simply removing the implant. Another drawback is that the components diffuse into systemic circulation, requiring careful long-term toxicological evaluation of hyrolysis products of the biopolymer making up the matrix. Various mechanisms are involved in the release of the active drug: these include erosion; diffusion; a combination of both, and the cleavage of a covalent linkage between the drug and the polymer backbone. Systems currently being developed include devices made of of: 1) polylactin and/or poly-glycolic acid; 2) polymers derived from e-caprolactone; 3) polypeptide polymers; 4) ploy-glutamic acid to which steroids are covalently bound, and 5) polyorthoester known as Chronomer.