Water-soluble phenylpyridazine derivative and medicine containing the same

A phenylpyridazine derivative represented by the formula (1):

• wherein:
• R1 is optionally substituted or unsubstituted alkyl, or substituted or unsubstituted alkenyl;
• f
• R2 and R3 each independently represents hydrogen or alkyl, hydroxyalkyl, dihydroxyalkyl or alkynyl, or R2 and R3 are fused together with the adjacent nitrogen atom to form a substituted or unsubstituted, nitrogen-containing, saturated heterocyclic group;
• X, Y and Z each independently represents hydrogen or halogen, substituted or unsubstituted alkyl, alkoxy, alkylthio, alkylsulfinyl or alkylsulfonyl, or substituted or unsubstituted aryl;
• and
• n stands for a number of from 1 to 5;
• with the proviso that R2 and R3 are not hydrogens or the same C1-C3 alkyl groups at the same time when R1 is a benzyl group or a C1-C3 alkyl group;
• or a salt thereof.