Anton Schindler

Biodegradable drug delivery systems based on aliphatic polyesters: application to contraceptives and narcotic antagonists.

The classes of polymer which form the basis of different types of drug delivery systems are discussed, and the relationships between the chemical structure of the polymer and its permeability, morphology, biodegradability, and mechanical properties are considered, using polyesters as specific examples. Studies of the permeability and biodegradability of poly epsilon-caprolactone), poly(DL-lactic acid), and various copolymers are described and used to illustrate how these properties may be varied by the choice of polymer structure. An induction period prior to bioerosion of these polymers, coupled with high permeability, permits their use as reservoir devices (capsules) which exhibit constant, diffusion-controlled drug release rates and which erode after the drug is exhausted. The applications of this approach to the long term delivery (1 year) of levonorgestrel, a contraceptive agent, and the short term delivery (1-2 months) of naltrexone, a narcotic antagonist, are described.

The kinetics of drug cleavage and release from matrices containing covalent polymer-drug conjugates

Abstract The kinetic expressions for release of a drug formed by the first-order cleavage of drug-polymer conjugates in a solid polymer film are derived from Ficks second law. It is shown that nearly zero order kinetics can be achieved with certain combinations of the drug diffusion coefficient, the cleavage rate constant and the film dimensions.