Abstract: BDDM iv 3～6 mg/kg showed effects against aconitine induced arrhythmias in rats (p<0.05) and decreased the incidence of adrenaline-chloroform induced arrhythmias significantly in rabbits. The dose of ouabain necessary to induce ventricular premature beats, ventricular tachycardia and cardiac arrest in guinea pigs was markedly increased by prior administration of BDDM. When treated with BDDM the BaCl₂-induced arrhythmias in rats changed immediately into sinus rhythm and lasted more than 7 min. The incidence of ventricular premature beats and ventricular tachycardia yielded by left coronary ligation in rats reduced significantly by iv BDDM 6 mg/kg. BDDM produced a bradycardia, but did not block the isoprenaline-induced tachycardia.