Preparation and release kinetics of hydrochlorothiazide from butyl half-ester of PVM/MA microcapsules

This study describes the principle of a simple rapid method for encapsulating hydrochlorothiazide in butyl half-ester of polyvinyl methyl ether-maleic anhydride copolymer to produce a controlled release dosage form. Unplasticized microcapsules and microcapsules plasticized with Tween 80 and castor oil were prepared. Particle size distribution, flow properties and drug content of microcapsules suggested the suitability of the method for encapsulating a wide variety of materials. The in-vitro release rate was studied as a function of core: coat ratio, type and concentration of plasticizer. Various release mechanisms were considered but no single mechanism can explain all the data completely.