Preparation and in Vitro Evaluation of Sustained-Release Suppositories Containing Microencapsulated Indomethacin

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Abstract
Microencapsulation of indomethacin (IM) was carried out by a simple coacervation method using ethylcellulose. To control the release of IM, its surface was modified by dry-blending it with a carboxy-vinyl polymer (Hiviswako 104, HW) by pulverization in an automatic ceramic mortar before encapsulation. Suppositories containing intact IM and microencapsulated IM (IM-MC) were prepared by the fusion method. Dissolution and release testing of the IM-MC and of the suppositories were carried out by the method of JPX and Muranishi et al., respectively. The dissolution rate of microencapsulated intact IM decreased as the content of the coacervation-inducing agent, polyethylene (PE), was increased. The release rate profile of the suppositories containing these microcapsules did not show an rapid zero-order release, and the release rate was rapid without PE. When the PE content was 1% (w/v), the release rate was too slow and a large portion of IM remained in the IM-MC. On the other hand, suppositories containing microencapsulated HW-modified IM (HW/IM = 1/1) showed an apparent zero-order release profile and about 100% of the IM in the IM-MC was released. These results showed that the surface modification of IM with HW before encapsulation is a good method to prepare sustained-release suppositories containing IM-MC.

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