Abstract: A method for solubilizing a pyridonecarboxylic acid or a pharmacologically acceptable salt thereof, which comprises adding an arylcarboxylic acid of the formula (I):L.sup.1 --R.sup.1 COOH (I)wherein L.sup.1 is an optionally substituted heterocyclic group or aryl group having not more than 14 carbon atoms, and R.sup.1 is an optionally substituted alkyl group having not more than 4 carbon atoms or a single bond, to the pyridonecarboxylic acid or the pharmacologically acceptable salt thereof, a solubilizer thereof and an aqueous solution containing a solubilized pyridonecarboxylic acid. According to the solubilization method of the present invention, the solubility of pyridonecarboxylic acid compounds and salts thereof at near physiological pH can be increased, thereby making the production of an aqueous solution to be used as an eye drop, nasal drop, ear drop and the like possible.

Abstract: An aqueous agent comprising at least one arginine amide selected from the group consisting of (2R,4R)-4-methyl-1-[N.sup.2 -((RS)-3-methyl-1,2,3,4-tetrahydro-8-quinolinesulfonyl)-L-arginyl]-2-piper idinecarboxylic acid, monohydrate thereof and pharmacologically acceptable salts thereof, and at least one compound selected from the group consisting of cyclodextrin and caffeine; a method for improving the solubility of arginine amide in water, comprising adding at least one compound selected from the group consisting of cyclodextrin and caffeine; and a method for stabilizing arginine amide in water, comprising adding caffeine. According to the present invention, the solubility of arginine amide in water can be enhanced to, for example, a concentration permitting inhibition of fibrin formation at the time of entoptic operation. In addition, the stability of arginine amide in water can be enhanced with less irritation of the eye.