Studies on microencapsulation. Part IV: Effect of ethylene-vinyl acetate as a coacervation-inducing agent on the production and release behavior of chlorpromazine hydrochloride microcapsules and tabletted microcapsules

Abstract

A highly water-soluble drug, chlorpromazine hydrochloride, was microencapsulated by phase separation using ethylene-vinyl acetate (EVA) as a coaceruation-inducing agent. The effect of EVA concentration on the preparation, micromeritic and drug release properties of chlorpromazine hydrochloride microcapsules and tabletted microcapsules was studied. Microcapsules were prepared by the deposition of ethyl cellulose round solid chlorpromazine hydrochloride particles, using 0–6% EVA as a coacervation-inducing agent. The particle size of the microcapsules decreased with increasing EVA concentration. The surface topography of the microcapsules became compact and the wall thickness was increased by increasing EVA concentration. Atmospheric stability and powder flowability were also affected by the EVA concentration used. Moreover, the release rate from untabletted or tabletted microcapsules was also influenced by the concentration of EVA. The thicker wall and less porous, more compact surface structure were responsible for the release of drug from untabletted microcapsules. However, the reduced surface area and porosity of the tabletted microcapsules, and the ethyl cellulose content of the insoluble tabletted micro-capsule matrix were important in drug release from tabletted microcapsules.