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Abstract

Eudragit RS100 microcapsules containing Aspirin as a model drug was prepared using solvent evaporation technique. The drug was dispersed in the organic phase and poured into the aqueous phase with stirring until microcapsules formation. The product was collected by filtration and air dried. The particle size analysis of the products was done and normal distribution curve showed for the same size range of different theoretical drug content, microcapsules had different size distribution. The sphericity of the microcapsule was greatly affected by the theoretical drug loaded. The mean microcapsule size decreased upon increasing the percent of theoretical drug content and then increased again. The surface of spherical microcapsule was smooth and no drug crystals attached to the surface. It was noticed drug crystals in the microcapsule structure. The mean actual drug content was markedly higher than the theoretical one. In the same product prepared with the same theoretical drug content, there was a relationship between the actual drug content and the product particle size. These findings were explained according to the division of emulsified microcapsule during preparation by division mechanism. In this division mechanism, there are two forces; one is the viscosity of the emulsified microcapsule which depends upon the polymer content. This force works against emulsified microcapsule division. The second is the drug solid particle weight in the emulsified microcapsule droplets and the stirring force effect on it which creates and potentiates the division mechanism. These two interacted forces, may be, the controlling factor for the resulting findings.