| 摘要 |
A method for stabilizing an aqueous solution containing a pyrazoloacridone derivative or a pharmaceutically acceptable salt thereof, comprising adding an acid to an aqueous solution containing a pyrazoloacridone derivative represented by the following formula (I) (hereinafter referred to as Compound (I)): <CHEM> wherein R<1a>, R<1b>, R<1c> and R<1d> independently represent hydrogen, a lower alkyl group, -(CH2)p-X (wherein p is an integer of 1 to 6; and X represents a hydroxyl group, a lower alkoxy group, or -NR<2a>R<2b> (wherein R<2a> and R<2b> independently represent hydrogen, a lower alkyl group, -(CH2)m-Y (wherein m is an integer of 1 to 6; and Y represents a hydroxyl group, a lower alkoxy group, or -NR<3a>R<3b> (wherein R<3a> and R<3b> independently represent hydrogen or a lower alkyl group)), or R<2a> and R<2b> form a heterocyclic group together with the nitrogen atom adjacent thereto)), or -CH((CH2)nOH)2 (wherein n is an integer of 1 to 5) or a pharmaceutically acceptable salt thereof; substituting the air in a well-closed container containing the aqueous solution with an inert gas; and sealing the container, and a well-closed container containing an aqueous solution containing Compound (I) or a pharmaceutically acceptable salt thereof and an acid, wherein the air in the well-closed container is substituted with an inert gas. |
