Poly (propylene-ram-epsilon-caprolactone carbonate) (PPCL) and poly ( propylene carbonate) ( PPC) were synthesized by ring-opening copolymerization from carbon dioxide, propylene oxide ( PO) and epsilon-caprolactone ( CL) using a polymer-supported bimetallic complexes ( PBM) as catalyst. PPC and PPCL microspheres containing a 5-alpha reductase inhibitor, finasteride were elaborated by a conventional oil-in-water (O/W) emulsion-solvent evaporation method. The effects of polymer used on microspheres morphology, size, drug loading, encapsulation efficiency and drug release behaviors were examined. In vitro drug release of these microcapsules was performed in a pH 7.4 phosphate-buffered solution. A prolonged in vitro drug release profile was observed. The release profiles of finasteride from PPC and PPCL microcapsules were found to occur with a burst release followed by a gradual release phase. Drug release rates were dependent upon the properties of the polymer in the microspheres, the higher hydrolytic activity of polymer provided faster release rate.