Controlled release of polypeptides and other macromolecules.

The use of polymeric matrices for the controlled release of polypeptides and other macromolecular drugs is reviewed. Three principal mechanisms of release include diffusion of the polypeptide through the polymer, erosion of the polymer matrix, and the application of magnetic fields to force more drug out of the matrix. The diffusion controlled systems generally utilize ethylene-vinyl acetate copolymer. The advantage of these systems is facile manipulation of the pore structure to obtain desired release kinetics. Release of many different polypeptides from these systems for periods of months has been demonstrated. Bioerosion provides the advantage that the polymer system does not need to be retrieved. Magnetism provides a mechanism whereby desired increases and decreases in polypeptide release rates can be achieved on demand.