Abstract
Preparation of ethylcellulose microcapsules containing theophylline was performed by simple non-solvent addition and emulsion non-solvent addition methods in the presence of polybutadiene or polyisobutylene as a protective colloid. The effects of the protective colloids upon the properties of microcapsules with respect to the size distribution, drug content, ethylcellulose loss and porosity were characterized. The results indicate that, in the presence of an appropriate amount of the protective colloid, the extent of aggregation was reduced and the surface became smoother and less porous. Mononucleated microcapsules were obtained by the emulsion non-solvent addition method in the presence of polyisobutylene. Owing to the occurrence of aggregation, the theophylline release from microcapsules appeared to follow the diffusion-controlled matrix model, the release rate being dependent upon the extent of aggregation and the porosity of microcapsules.