Effects of protective colloids upon properties of ethylcellulose microcapsules prepared from various non-solvent addition methods

Preparation of ethylcellulose microcapsules containing theophylline was per formed by simple non-solvent addition and emulsion non-solvent addition met hods in the presence of polybutadiene or polyisobutylene as a protective co lloid. The effects of the protective colloids upon the properties of microc apsules with respect to the size distribution, drug content, ethylcellulose loss and porosity were characterized. The results indicate that, in the pr esence of an appropriate amount of the protective colloid, the extent of ag gregation was reduced and the surface became smoother and less porous. Mono nucleated microcapsules were obtained by the emulsion non-solvent addition method in the presence of polyisobutylene. Owing to the occurrence of aggre gation, the theophylline release from microcapsules appeared to follow the diffusion-controlled matrix model, the release rate being dependent upon th e extent of aggregation and the porosity of microcapsules.