Abstract

Microencapsulation by ethylene vinyl acetate copolymer (EVA) and the resulting microcapsules were investigated. EVA microcapsules of indomethacin were prepared by an emulsion solvent evaporation method employing various proportions of coat and core materials and chloroform as solvent for the polymer EVA. The microcapsules are spherical, discrete and free flowing. Microencap-sulation efficiency was in the range of 87-99% lndomethacin release from the microcapsules was slow and extended over more than 12 h and depended on coat: core ratio, wall thickness and size of the microcapsules. Drug release was diffusion controlled and followed first order kinetics. Good linear relationships were observed between wall thickness and release rate and T50 (time for 50% release) values. Some microcapsules fulfilled the official (USP XXIII) dissolution rate test specification of indomethacin extended release capsules. Differential scanning calorimetry (DSC) indicated no Interaction between the coat polymer (EVA) and the core (indomethacin).