Provided is a pharmaceutical preparation including a polymerized camptothecin derivative that is obtained by bonding a camptothecin derivative having nanoparticle-forming properties by associating in an aqueous solution, to a polymer carrier, the pharmaceutical preparation composition having enhanced preparation stability. Particularly, a pharmaceutical preparation maintaining nanoparticle-forming properties and camptothecin derivative bonding stability, which are important factors, and having excellent storage stability is provided.Disclosed is a pharmaceutical preparation including a block copolymer in which a polyethylene glycol segment is linked to a polyglutamic acid segment including a glutamic acid unit having a camptothecin derivative bonded thereto； and a saccharide. The pharmaceutical preparation forms associates in an aqueous solution, and the ratio of change in the scattered light intensity of the associates of the pharmaceutical preparation obtained after the pharmaceutical preparation is stored for 4 weeks at 40° C. under light-shielded conditions, is 20% or less.
