Disclosed is a container other than an ampule, which is filled with an aqueous solution containing a pyrazolone derivative, a physiologically acceptable salt thereof, or a hydrate or solvate of the derivative or salt as an active ingredient. The container is a plastic container filled with an aqueous solution containing a pyrazolone derivative (e.g., 3-methyl-1-phenyl-2-pyrazolin-5-one), a physiologically acceptable salt thereof, or a hydrate or solvate of the derivative or salt as an active ingredient.
