Bucainide is a potent cardiac depressant and antiarrhythmic agent. The antiarrhythmic effect was demonstrated in the following animal models: mouse chloroform-induced ventricular arrhythmias, refractory period prolongation in guinea pig isolated atria, aconitine-induced atrial arrhythmias in the dog, ventricular arrhythmias following coronary artery ligation in the dog, and ouabain-induced ventricular tachyarrhythmias in the dog. The drug also possesses local anesthetic effects and is a weak central nervous system depressant. Studies with the radiolabeled drug in rats and dogs also demonstrated the drug's large volume of distribution, and its initial rapid disappearance from the blood. Tissue distribution studies in the rat after administration of the radiolabeled drug showed that bucainide is rapidly taken up by the tissues.