A pharmaceutical composition including drug-containing nanoparticles having an average particle diameter of from 10 nm to 150 nm, the pharmaceutical composition being obtained by mixing water with a poorly water soluble drug-containing, water miscible solution that contains a poorly water soluble drug having a water solubility of 50 µg/mL or less, a water soluble copolymer having a repeating unit represented by the following Formula (1), and a water miscible miscible solvent, wherein in Formula (1), n : m is within a range of from 0.25 : 0.75 to 0.95 : 0.05, R represents an alkyl group which may have a substituent,R1 and R2 each independently represent a hydrogen atom or a methyl group, and Me represents a methyl group and a preparation for oral administration, which includes the pharmaceutical composition.
