A pharmaceutical composition containing a water-soluble drug in a semi-permeable layer is provided to release the drug slowly in a constant rate, minimize delay of initial release time, reduce the production costs, reduce environmental pollution, minimize chemical interaction between different drugs, and enhance compliance of a patient. A pharmaceutical composition for sustained delivery of drug contains (a) a core containing a water-soluble active ingredient such as metformin and pharmaceutically acceptable excipients, and (b) a semi-permeable outer layer formed on the surface of the core, containing polymer such as polyvinylacetate for forming semi-permeable layer and water-soluble ingredient, and optionally a second outer layer formed on the semi-permeable layer, containing a second active ingredient such as glymepyride. The pharmaceutical composition for the sustained delivery of the drug additionally comprises water-soluble polymer at the semi-permeable outer layer.본 발명은 수용성 활성성분 (선택적으로, 수용성 중합체도 함께)이 하나 이상의 반투과성 외층에 존재하며 활성성분을 서방형으로 전달하는 수단을 제공한다.상기와 같이 본 발명은 하나 이상의 외층이 반투과성이어서 액체 매질이 삼투압으로 인해 반투과성 외층를 통과하며 반투과성 외층의 수용성 중합체 및 수용성 활성 성분과 코어의 활성 성분을 녹여 액체 매질에 활성 성분을 서방형으로 전달하는 수단을 제공한다.
