Preparation of sustained release microparticles with improved initial release property.

The objective of this study was to investigate the potential of various formulation strategies to achieve sustained release of the peptide, from injectable poly(D,L-lactide-co-glycolide) (PLGA) and d-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) microparticles. The microparticles were prepared by a solvent evaporation method. Peptide loaded PLGA microparticles exhibited a pronounced initial burst release (22.3% in 1 day) and lag phase in phosphate buffer of pH 7.0. In contrast, blending of 5.0% TPGS (8.6% release in 1 day) or 10.0% TPGS (5.5% release in 1 day) in PLGA microparticles reduced initial burst release and the lag-phase time. Incorporation of TPGS in PLGA microparticles further increased drug release, attributable to improved drug encapsulation, increased particle size, and exempt of pores. PLGA+ 10.0% TPGS composite microparticles exhibited the most desirable drug release among all the formulations tested, and demonstrated triphasic release after minimal initial burst.