Drug-containing nanoparticles are provided that enable effective targeting and sustained-release of a water-soluble, non-peptide, low-molecular weight drug and cause reduced accumulation of the drug in the liver. The nanoparticles containing a water-soluble, non-peptide, low-molecular weight drug are obtained by hydrophobicizing the water-soluble, non-peptide, low-molecular weight drug by a metal ion, and reacting the hydrophobicized drug with a poly(lactic acid)-polyethylene glycol block copolymer or a poly(lactic-co-glycolic acid)-polyethylene glycol block copolymer. The nanoparticles have favorable targeting and sustained-release properties and cause reduced accumulation of the drug in the liver.
