Provided is a novel pharmaceutical composition (antipruritic agent) that is useful for prophylaxis or treatment of itch in conditions such as dermal pruritus. More specifically, provided is a pharmaceutical composition (antipruritic agent) for treatment of itch comprising as an active ingredient a naphthalene compound of the following formula (I): wherein the ring A is a heterocyclic group of the following formula: a hydrate thereof or a pharmaceutically acceptable salt thereof.
