| abstract |
A multi-stage oral drug controlled-release system is disclosed, as well as a preparation for maintaining the drug blood concentration at a desired level for a prolonged time. The system operates by releasing the drug at a constant rate through stepwise control of drug release following administration of the preparation. More specifically, the multi-stage oral drug controlled-release system involves the stepwise release of drug-containing granules from an inner matrix, which is surrounded by a coating or release-modifying layer. The granules contain an active drug and a carrier material in size of 0.1˜1 mm. The carrier material is hydrophobic when the drug has a water-solubility of 1 mg/ml or more, and is hydrophilic when the drug has a water-solubility of less than 1 mg/ml. The inner matrix, in which the drug-containing granules are embedded, is formed from swelling and erodible polymer(s) and swelling-regulating material(s). The release-modifying layer is composed of a hydrophobic release-modifying polymer, a hydrophilic release-modifying polymer, pH-dependent release-modifying polymer or mixtures thereof. |