Acta Pharm. 50 (2000) 57-63
Microcapsules with the calcium channel blocker, verapamil hydrochloride, were prepared by the emulsion-solvent evaporation technique, using ethylcellulose and different enterosoluble polymers as wall forming materials. The effect of different polymers and polymer-to-drug ratio on microcapsule properties has been studied. Incorporation of acidoresistant polymer in formulation caused differences in the particle size and drug loading efficacy, compared to the series containing ethylcellulose only as a wall forming material. Drug dissolution rate at pH 6.8 increased when a mixture of ethylcellulose and acidoresistant polymer was used as a coating material. Drug dissolution rate at pH 1.5 depended on the portion of the acidoresistant polymer in the coating mixture and core to coating ratio. The drug release obeyed the Higuchi matrix model.
Keywords: microcapsules, verapamil HCl, sustained release, ethylcellulose, acidoresistant polymers, emulsion-solvent evaporation method