Vancomycin release from blended polyester microspheres.

O/W emulsification with solvent evaporation was used to fabricate spherical (5-100 microm) vancomycin loaded microspheres, either smooth surfaced with macroporous interior (PLCG 50:50), smooth surfaced and monolithic (PEAD), smooth surfaced (50% PEAD/50% PLCG 50:50), or with a slightly rugose and possibly microporous surface (75% P[HB-HV]/25% PLCG 50:50). Blending PLCG 50:50 with either PEAD or P(HB-HV) marginally increased microsphere diameter, and vancomycin incorporation resulted in the deposition and embedding of vancomycin particles at the microsphere surface. The mean vancomycin encapsulation efficiencies for PLCG 50:50, PEAD, and 50% PEAD/50% PLCG 50:50 were high (>64%) but values for 75% P(HB-HV)/25% PLCG 50:50 were lower and not significantly influenced by the extent of vancomycin loading. Vancomycin release profiles were characterized by an initial burst release followed by a low level sustained release extending up to 20 days. The extent of both release phases depended on the composition of the fabrication polymer and the incubation medium used. The initial burst release of vancomycin was greatest from 75% P(HB-HV)/25% PLCG 50:50 microspheres. However, the mean total cumulative release of vancmycin from PLCG 50:50, PEAD, and 50% PEAD/50% PLCG 50:50 microspheres was significantly greater and detectable over a longer period of time in newborn calf serum than in Hank's buffer. Irrespective of the incubation medium used, blending PEAD with PLCG 50:50 only marginally increased the mean cumulative release of vancomycin from microspheres.