An antihistamine with anticholinergic and antiserotonergic activities; histamine H1 receptor antagonist (Ki = 3.9 nM); inhibits histamine- and acetylcholine-induced contractions in isolated guinea pig ilium and 5-HT-induced contractions in isolated rat uterus (EC50s = 6.5, 10, and 14 nM, respectively); delays the onset of dyspnea induced by aerosolized histamine, 5-HT, or acetylcholine in guinea pigs; prevents histamine-induced lethality in guinea pigs and paw edema in mice (ED50s = 9 and 68 μg/kg, respectively); increases survival in guinea pig and mouse models of anaphylactic shock (PD50s = 0.024 and 0.019 mg/kg, respectively)