Poly(butylene-co-epsilon-caprolactone carbonate) (PBCCL) was successfully synthesized via terpolymerization of carbon dioxide, 1,2-butylene oxide (BO), and epsilon-caprolactone (epsilon-CL). epsilon-CL was inserted into the backbone of BO-CO2. The glass transition temperature (T-g) and the decomposition temperature (T-d) of PBCCL were much higher than those of poly(butylene carbonate) (PBC). The degradation rate of PBCCL was higher than that of PBC in a pH 7.4 phosphate-buffered solution. epsilon-CL offered an ester structural unit that gave the terpolymers remarkable degradability. PBC and PBCCL microcapsules containing a hydrophilic antibiotic drug pazufloxacin mesilate (PZFX) were elaborated by solvent evaporation method based on the formation of double W/O/W emulsion. Microcapsules were characterized in terms of the morphology, size, amount of encapsulated, and encapsulation efficiency. The results showed that the microcapsules had smooth and spherical surfaces, and the mean diameter of the microcapsules was in the range of 0.5-1 mu m. Of all, 87.90% drug encapsulation efficiency has been achieved for microcapsules of 38.21% drug loading. In vitro drug release of these microcapsules was performed in a pH 7.4 phosphate-buffered solution. The release profiles were investigated from the measurement of PZFX presented in the release medium at various intervals. The release profiles of PZFX from PBC and PBCL microcapsules were found to be bipbasic with a burst release followed by a gradual release phase. The release rate of PZFX from the microcapsules increased with increasing the content of epsilon-CL inserted into the copolymers. It showed that the release profiles of PZFX were highly polymer-dependent. (C) 2007 Wiley Periodicals, Inc.