a new method for making polymeric systems for the sustained release of macromolecular drugs is described . the method consists of mixing drug and polymer , e . g . ethylene - vinyl acetate copolymer powders below the glass transition temperature of the polymer , and compressing the mixture at a temperature above the glass transition point . the macromolecule is not exposed to organic solvent during the fabrication process . the sustained release and bioactivity of macromolecules is unchanged throughout the pressure casting and release processes .