The present study involves the preparation and evaluation of buoyant microspheres using famotidine as a model drug for prolongation of gastric retention time. The microspheres were prepared by the solvent evaporation method using different polymers i.e., acrycoat S100 and cellulose acetate. The size or average diameter (davg) characterized by optical microscopic method and surface morphology (internal texture) was recognized by the scanning electron microscopic method, which showed that fabricated microspheres were spherical with a smooth surface. The presence of pores was detected; this indicated leaching of the drug during the dissolution without gelation of polymeric surface. Effects of the stirring rate during preparation and polymer concentration on the size of microspheres and drug release were also observed by in vitro drug release kinetic studies. The prepared microspheres exhibited prolonged drug release (18 h). The cumulative release of famotidine signiÞ cantly decreased with increasing polymer concentration (P < 0.05). The increased density of the polymer matrix at higher concentrations resulted in an increased diffusional path length. This may decrease the overall drug release from the polymer matrix. Furthermore, smaller microspheres are formed at a lower polymer concentration and have a larger surface area exposed to dissolution medium, giving rise to faster drug release that remained buoyant for more than 12 h. The mean particle size increased and the drug release rate decreased at higher polymer concentrations. No signiÞ cant effect of the stirring rate during preparation on drug release was observed. In vitro studies demonstrated diffusion-controlled drug release from the microspheres.
Key words: Buoyant microspheres, famotidine, gastric treatment.
