Formation mechanism and release behavior of polymeric microspheres containing disodium norcantharidate

摘要

Disodium norcantharidate (DSNC) was encapsulated in polymeric microspheres by s/o/w solvent evaporation technique, and the formation mechanism and release behavior were investigated. The microspheres were found to be porous, and the porosity was demonstrated to be a result of the osmotic effect of DSNC, a highly water soluble drug salt. During the microsphere preparation, water diffused into the emulsion droplets and dissolved the drug particles. Thereafter, the drug generated osmotic effect which drove the water to flow into the emulsion droplets more quickly thus forming an inner water phase. As the water influx proceeded, the state of the emulsion was transferred from s/o/w to w/o/w, thus resulting in the porosity of the resulting microspheres after drying. The drug release behavior was carried out in dissolution mediums of different osmotic pressure achieved by adding different amount of dextrose. The result indicated that the initial release of the drug was controlled by a combination of osmotic effect and diffusion, and the later drug release was mainly controlled by diffusion. This study demonstrated that the osmotic effect of DSNC not only governed the particle formation but also made an important contribution to the release behavior of the DSNC microspheres.