This invention the metasuchin derivative and the weight average molecular weight approximately 5,000 or approximately 40,000 the lactic acid which is - regards the sustained-release formulation which contains glycol Acid copolymer or that salt. The sustained-release formulation of this invention, shows the sustained-release which chemical compound (i) or that salt stabilizes over long term shows chemical compound (i) or the medicinal effect of that salt in addition over long term. In addition, as for the sustained-release formulation of this invention convenience of the patient improved with the decrease of frequency of dosage, it is the formulation which is superior as a medicine on clinical.本発明はメタスチン誘導体及び重量平均分子量が約5,000ないし約40,000である乳酸―グリコール酸共重合体またはその塩を含有する徐放性製剤に関する。本発明の徐放性製剤は、長期にわたって化合物(I)またはその塩の安定した徐放性を示し、また長期にわたって化合物(I)またはその塩の薬効を発揮する。また、本発明の徐放性製剤は投与回数の減少により患者の利便性が向上した、臨床上の医薬として優れた製剤である。
