Agents for treating neuropathic pain

A compound as shown in the following formula (I)

• (wherein A represents a phenyl group or a monocyclic aromatic heterocyclic ring each optionally substituted by R1 and/or R2;
• R1 and R2 represent, independently of each other, a group selected from the group consisting of halogen atom, trifluoromethyl group, trifluoromethoxy group, nitro group, cyano group, lower alkoxycarbonyl group, amino group unsubstituted or mono- or di-substituted by lower alkyl-groups, carbamoyl group unsubstituted or mono- or di-substituted by lower alkyl groups, sulfamoyl group unsubstituted or mono- or di-substituted by lower alkyl groups, unprotected or protected hydroxyl group, unprotected or protected carboxyl group, lower alkoxy group, lower alkyl group, lower alkylthio group, lower alkylsulfinyl group, lower alkylsulfonyl group and lower alkanoyl group;
• R3 represents hydrogen atom or lower alkyl group;
• R4 represents hydrogen atom or a lower alkyl group;
• R5 represents ethoxy group or isopropoxy group;
• X represents CH(OH)— or methylene group;
• and Z represents a single bond or methylene group unsubstituted or substituted by unprotected or protected hydroxyl group, or pharmaceutically acceptable salt thereof.