A pharmaceutical composition for modified release, comprising (1) (R)-2-(2-aminothiazol-4-yl)-4'-[2-[(2-hydroxy-2-phenylethyl)amino]ethyl]acetic acid anilide, or a pharmaceutically acceptable salt thereof, (2) at least one additive which ensures penetration of water into the pharmaceutical composition and which has a solubility such that the volume of water required for dissolving 1 g of the additive is 10 mL or less, and (3) a hydrogel-forming polymer having an average molecular weight of approximately 100,000 or more, or a viscosity of 12 mPa·s or more at a 5% aqueous solution at 25°C is disclosed.
