Effect of Magnesium Stearate in Preparation of Eudragit RS-Microcapsules Containing Drugs

Abstract

A microencapsulation of drugs using Eudragit RS which are copolymers synthesized from acrylic and methacrylic acid esters with a low content of quaternary ammonium groups, was investigated. The preparation is based on dispersion of methylene chloride containing drugs, Eudragit RS and magnesium stearate in purified water, followed by evaporation of methylene chloride using a well-regulated water bath. Magnesium stearate was used to reduce the flocculation of microcapsules in the preparation. Although 42 drugs were examined, only three drugs (sulfamethizole, furosemide and piretanide) were successful. The microcapsules just after separation from purified water were swollen due to hydrophilic groups of Eudragit RS. Furthermore, the swelling tendency increased in linearly with increasing addition percentages of magnesium stearate. The most suitable percentages of magnesium stearate for the preparation of microcapsules could be confirmed in this experiment. The microcapsules obtained after drying under reduced pressure were uniform and free-flowing particles. The dissolution rates of drugs from these microcapsules were relatively small compared to that from drug powders.