A histamine H1 receptor antagonist (Ki = 2.3 nM) and first generation antihistamine; competes with [3H]diltiazem for binding to the benzothiazepine site on rat cardiomyocytes (Ki = 1.08 nM); decreases negative inotropic activity in isolated guinea pig left atria by 76% (EC50 = 250 nM); decreases negative chronotropic activity in guinea pig spontaneously beating isolated right atria by 48%