PROBLEM TO BE SOLVED: To provide a sustained release formulation capable of improving patient convenience, relieving pain, and exerting its medicinal effect over a long period of time by reducing side effects and decreasing the number of administrations.SOLUTION: According to the present invention, there is provided a sustained-release formulation comprising: a metastin derivative represented by the formula (I) or a salt thereof； and a lactic acid-glycolic acid copolymer having a weight average molecular weight of about 5,000 to about 40,000, preferably about 6000 to 20000 or a salt thereof. Ac-D-Tyr-Hyp-Asn- Ac-D-Tyr-Hyp-Asn-Thr-Phe-AzaGly-Leu-Arg(Me)-Trp-NH2 (I)EFFECT: The formulation can exhibit the medicinal effect by the stable sustained release of the metastin derivative or the salt thereof, and can be used as a preparation improved in patient convenience due to a decrease in the number of administrations.SELECTED DRAWING: None【課題】副作用の軽減、投与回数の減少による患者の利便性向上や苦痛解消、及び長期間にわたる薬効発揮が可能な徐放性製剤の提供。【解決手段】式（Ｉ）で表されるメタスチン誘導体又はその塩及び重量平均分子量が約５,０００～約４０,０００、好ましくは約６０００～２００００である乳酸―グリコール酸共重合体又はその塩を含有する徐放性製剤。Ac-D-Tyr-Hyp-Asn-Thr-Phe-AzaGly-Leu-Arg(Me)-Trp-NH2（I）【効果】前記製剤は、前記メタスチン誘導体又はその塩の安定した徐放性による薬効発揮が可能となり、投与回数の減少による患者の利便性が向上した製剤として使用できる。【選択図】なし
