A compound having the following formula (II) or its pharmacologically acceptable salt is used as a P2X
4
receptor antagonist:
in which
R
11
represents hydrogen or an alkyl group having 1-8 carbon atoms;
R
21
represents an alkyl group having 1-8 carbon atoms, an alkoxy group having 1-8 carbon atoms, an alkyl group having 1-8 carbon atoms and having 1-3 halogen substituents, or hydroxyl; and
R
31
is hydrogen or a halogen atom.