Found out is a pharmaceutical composition that sustained-releases a drug for a long term after administration into the body. Provided is a pharmaceutical composition comprising a drug and a polypeptide represented by Ac-(Arg-Ala-Asp-Ala)4-NH2, and further containing an organic solvent selected from the group consisting of polyethylene glycol, dimethyl sulfoxide, glycofurol, and N-methylpyrrolidone.