Omar Mady, IJPSR, 2014; Vol. 5(7): 2620-2630. E-ISSN: 0975-8232; P-ISSN: 2320-5148 International Journal of Pharmaceutical Sciences and Research 2620 IJPSR (2014), Vol. 5, Issue 7 (Research Article) Received on 17 January, 2014; received in revised form, 05 March, 2014; accepted, 14 May, 2014; published 01 July, 2014 STUDYING THE EFFECT OF DISPERSED DRUG CRYSTAL IN THE ORGANIC PHASE ON THE ENCAPSULATION BY SOLVENT EVAPORATION TECHNIQUE; (1) EFFECT OF DRUG LOADING EXTENT ON THE PRODUCT SIZE ANALYSIS, MORPHOLOGY AND DRUG CONTENT Omar Mady Department of Pharmaceutical Technology, Faculty of Pharmacy, Tanta University, Egypt 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. INTRODUCTION: Incorporation of a drug within microcapsules plays a major factor on its release. Microcapsules can be classified according to the method of drug incorporation into reservoir type in which a solid or a liquid drug is enveloped in the polymer membrane and matrix system in which the drug is dissolved or dispersed in the polymer matrix 1 . These two types of microcapsule structures can be achieved by the use of solvent evaporation technique. QUICK RESPONSE CODE DOI: 10.13040/IJPSR.0975-8232.5(7).2620-30 Article can be accessed online on: www.ijpsr.com DOI link: http://dx.doi.org/10.13040/IJPSR.0975-8232.5(7).2620-30 When the drug is dissolved and/or dispersed in the microcapsule structure, its release has what is called Burst effect 2, 3 . In many cases, incomplete drug release occurs 2-6 . Mady et al 2 found that, the percent of drug loaded could not be increased more than 20%. Many trials were made to increase the percent of the actual drug content in the spheres. One of them involved the dispersion of drug in the organic phase which led to decrease the drug diffusion to the aqueous phase. Benoit et al 3 , tried to increase the actual drug content using theoretical drug content up to 60%. In every case, the authors found that the actual drug content was not more than 23% although the drug (5-flurouracil) was dispersed in the organic phase as drug crystals. Keywords: Division mechanism, Microcapsule, Eudragit RS100, Aspirin, Particle size distribution analysis, Drug content, Electron scanning microscopy Correspondence to Author: Omar Mady Assistant Professor of Pharmaceutical Technology, Department of Pharmaceutical Technology, Faculty of Pharmacy, Tanta University, Egypt E-mail: omer.mady@gmx.at