An object of the present invention is to find a pharmaceutical composition allowing a drug to be sustained-released over a long period time after in vivo administration. The present invention provides a pharmaceutical composition containing a drug and a polypeptide represented by Ac-(Arg-Ala-Asp-Ala)4-NH2, further containing an organic solvent selected from a group consisting of polyethylene glycol, dimethyl sulfoxide, glycofurol and a N-methylpyrrolidone.本發明係發現一種醫藥組成物，其係經投予於體內後藥物以長期間緩釋者。本發明係提供一種醫藥組成物，其係含有藥物以及以Ac-(Arg-Ala-Asp-Ala)4-NH2表示之多肽，並進一步含有選自聚乙二醇、二甲亞碸、四氫呋喃甲基聚乙二醇醚以及N-甲基吡咯啶酮所成群組之至少一種的有機溶劑。
