Aiming at improving drug efficacy, minimizing side effects and promoting patient compliance, extensive studies on drug delivery system (DDS) have been conducted. For example, implantable DDS has been investigated in order to achieve prolonged effects and/or deliver water-soluble drugs which are poorly absorbed by the gastrointestinal tract. Since implantable DDS is administered inside a body, drug carrier materials should be biocompatible and resistant against sterilization. Silicone has been

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... tensively used as a drug carrier material for implantable DDS, because it has appropriate features for such requirements. Drug release mechanism from silicone carrier differs depending on physicochemical properties of the drug. So far, there have been few reports on controlled release of insoluble drug and on simultaneous release of two kinds of water-soluble drugs. The purposes of this study are to establish methods for (1) continuous release of insoluble drug, and (2) release of two kinds of water-soluble drugs from silicone carrier. Polystyrene beads (PSTB) and proteins such as interferon (IFN) and human serum albumin (HSA) were used as model drugs. PSTB was released from silicone only when citric acid (CA) and sodium bicarbonate (SB) existed as additives. The release patterns of IFN and HSA were almost same in the case of matrix and covered-rod formulations, but double-layered formulation released them in different patterns. As far as we are aware, this is the first report on the release of insoluble drug from silicone and the controlled release of two kinds of water-soluble drugs.