Provided is a therapeutic and/or prophylactic agent for respiratory diseases, or a therapeutic and/or prophylactic agent for sodium channel-mediated diseases. A pharmaceutical agent which contains, as an active ingredient, a compound represented by formula (I) or a pharmacologically acceptable salt thereof. In formula (I), each of Ar1 and Ar2 represents a heteroaryl group or an aryl group； each of R1, R2 and R3 represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a halogenated C1-C6 alkyl group, a hydroxy C1-C6 alkyl group, a C1-C6 alkoxy C1-C6 alkyl group, a C3-C7 cycloalkyl group or a cyano group； each of R4 and R5 represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a halogenated C1-C6 alkyl group, a hydroxyl group, a hydroxy C1-C6 alkyl group, a C1-C6 alkoxy C1-C6 alkyl group, a C3-C7 cycloalkyl group or a C1-C6 alkoxy group； and n represents an integer of 1-3. In this connection, the heteroaryl group and the aryl group may have one or two groups that are independently selected from among a halogen atom, a C1-C6 alkyl group, a halogenated C1-C6 alkyl group, a hydroxyl group, a hydroxy C1-C6 alkyl group, a C1-C6 alkoxy C1-C6 alkyl group, a C3-C7 cycloalkyl group, a carboxyl group, a cyano group, an amino group, a C1-C3 alkylamino group and a di C1-C3 alkylamino group, and in cases where two groups are contained therein, the groups may be the same as or different from each other.
