Histamine H1 receptor antagonist. Also blocks hERG and KATP channels (IC50 values are 204 nM and 1.2 μM respectively). Inhibits the delayed rectifier K+ current (IKr) in guinea pig ventricular myocytes (IC50 = 50 nM). Activity prolongs QT and induces Torsades de pointes (TdP); cardiotoxic in vivo.