Preparation and in vivo evaluation of thienorphine-loaded PLGA microspheres

Thienorphine-loaded microspheres composed of poly(D,L-lactide-co-glycolide) were prepared by an O/W emulsion solvent evaporation method. HPLC was used to determine the drug loading and drug release, while a LC-MS-MS system was employed to analyze the plasma drug concentration. Results indicated that the PLGA particles obtained were spherical and of appropriate size. The formulation was stable during the test period. In vitro drug release from the microspheres was sustained for about 28 days mostly by the diffusion mechanism. The plasma drug concentration-time profiles were relatively smooth for about 28 days after subcutaneous injection of the drug-loaded microspheres to rats, compared with that for drug suspension. In vitro and in vivo correlation was established.