Electrophysiological effects of butoprozine on isolated heart preparations. Comparison with amiodarone and verapamil.

The electrophysiological effects of butoprozine, a relatively new antiarrhythmic agent, were investigated in sheep cardiac Purkinje fibres using a microelectrode technique and in frog atrial and ferret ventricular fibres using a double sucrose gap technique. Comparison was made with amiodarone and verapamil. Butoprozine increased the action potential duration like amiodarone, depressed the plateau phase like verapamil and decreased the amplitude and the maximum rate of depolarization. Pacemaker activity in Purkinje fibres and repetitive activity in frog atrium were inhibited by the three drugs. The inhibition of automaticity was related to a reduction of the slope of diastolic depolarization in both tissues by butoprozine and amiodarone. The results confirm that butoprozine possesses a potent antiarrhythmic activity. It acts by mechanisms common to amiodarone and verapamil.