ABSTRACT
The process of molecular diffusion through polymers and synthetic membranes has been used as an effective and reliable means of attaining not only the controlled release of drugs and pharmacologically active agents, but also of fertilizers, pesticides, and herbicides. Central to the development of controlled delivery systems is the synthesis of the principles of molecular transport in polymeric materials and those of pharmacokinetics and pharmacodynamics. Advances in controlled release technology have been rapid because polymer science has become sophisticated enough to incorporate into polymers tailor-made properties for each controlled release application. However, controlled release systems can impart other important advantages to active agents that are sufficient to elevate many products to commercial successes. Microcapsules and macrocapsules are the major controlled release reservoir systems with rate-controlling membranes. In capsules or microcapsules with erodible membranes, the mechanism of release can be the erosion and rupture of the barrier membrane.
