Microencapsulation of drugs by the coacervation technique using ethylcellulose and acrylate-methacrylate copolymer as wall materials.

In this study, ethylcellulose and acrylate-methacrylate copolymer (Eudragit RL 100, Eudragit RS 100) membranes were prepared by using appropriate types and amounts of plasticizers. Thirty percent and 20% of triacetin based on polymer weight were found to be appropriate plasticizers for ethylcellulose membranes and acrylate-methacrylate copolymer membranes, respectively. The ratios of 3:2 and 2:3 Eudragit RL 100: Eudragit RS 100 also gave transparent and flexible membranes. Cephalexin was chosen as a model drug. The coacervation technique was investigated for the preparation of cephalexin microcapsules. Ethylcellulose and acrylate-methacrylate copolymer corresponding to the above ratios were selected as wall materials of the microcapsules. The effects of core-to-wall ratios on the surface characteristics and dissolution of the microcapsules were also studied. The coacervation technique with ethylcellulose as wall material gave the higher yield (90%) of microcapsules. The release of cephalexin from ethylcellulose walled microcapsules was slow whilst the release from those of acrylate-methacrylate copolymer was faster. The increase of deposition of wall materials due to the decrease of the core-to-wall ratio resulted in a decrease of dissolution rate.