A Comparative Evaluation of Drug Release and Permeability of Ethylcellulose, Cellulose Acetate and Eudragit RS100 Microspheres

Abstract

Present study aims at comparative evaluation of drug release and permeability of diclofenac sodium loaded ethylcellulose (EC), cellulose acetate (CA) and eudragit (EU) microspheres. Microspheres of EC, CA and EU containing diclofenac sodium were prepared by an emulsification-solvent evaporation (oil-in-oil, o/o) method and were investigated for a comparative evaluation of various parameters. The microspheres were found discrete, free flowing, multinucleate, monolithic and spherical. About 5560% of all microspheres prepared were in the size range of -20+30 (715 m) mesh size. The encapsulation efficiency was in the range of 97.1106.4% with various polymers. The wall thickness of microspheres was in the range of 13.69-74.97m which depended on polymer employed and was directly proportional to polymer concentration. Diclofenac release from the microspheres was slow over longer periods of time and depended on the polymer used and coat:core ratio. Release was diffusion controlled and followed first order kinetics. Good linear relationships were observed between percent coat, wall thickness and release rate constant with all the three polymers. The slopes of percent coat vs release rate (k1) plots were found to be 0.4117, 0.2351 and 0.9762; and those of wall thickness (h) vs drug release rate (k1) plots were found 0.2549, 0.1863 and 0.7850 respectively for EC, CA and EU microspheres. The lower the slope the better is the controlling effect. Cellulose acetate exhibited better release-controlling effect than that of ethylcellulose and eudragit. The increasing order of diclofenac release rate and permeability observed with various microspheres was, cellulose acetate < ethylcellulose < eudragit RS100. The possible permeability of drug from the prepared porous micrsopheres could be due to osmotic pressure generated by diclofenac.