An aqueous drug in which the chemical decomposition of the compound represented by formula (1) or of a salt thereof is inhibited, and a method for producing said aqueous drug. An aqueous drug provided with: a solution (liquid A) that contains the compound represented by formula (1) or a salt thereof and that has a pH of 5.3 or less； and a dilution liquid (liquid B) that is mixed with the liquid A in order to prepare a solution to be administered.
