Cloperastine (INN) or cloperastin is an antitussive and antihistamine that is marketed as a cough suppressant in Japan, Hong Kong, and in some European countries. It was first introduced in 1972 in Japan, and then in Italy in 1981. The precise mechanism of action of cloperastine is not fully clear, but several different biological activities have been identified for the drug, of which include: ligand of the gamma1 receptor (Ki = 20 nM) (likely an agonist), GIRK channel blocker (described as "potent"), antihistamine (Ki = 3.8 nM for the H1 receptor), and anticholinergic. Cloperastine possesses dual activity. It also acts as a mild bronchorelaxant and has antihistaminic activity, without acting on the central nervous system or the respiratory center.