INFLUENCE OF MANUFACTURING PARAMETERS ON THE SIZE CHARACTERISTICS ANDTHE RELEASE PROFILES OF NIFEDIPINE FROM POLY(DL-LACTIDE-CO-GLYCOLIDE)MICROSPHERES

Empty or nifedipine-loaded biodegradable poly(DL-lactide-co-glycolide) microspheres were prepared by the solvent evaporation method. Spheric al microparticles of different size distribution were thus obtained. T he evolution of the mean diameter and the extent of size distribution as a function of different preparation parameters were studied. The me an particle diameter decreased when the stirring rate, the surface-act ive agent concentration and the internal phase volume were increased. Microspheres of 12, 18 and 83 mum, with different nifedipine payloads were obtained. The in vitro release of the drug was evaluated under si nk and non-sink conditions: the 12 and 18 mum microspheres provide the same linear profile for approx. 400 h. Under non-sink conditions, the 83 mum microspheres exhibit an S-shape release pattern.