Electrophysiological properties of butoprozine studied by multiple intracardiac recordings on the anaesthetized dog.

Electrophysiological effects of butoprozine (L 9394 Labaz) were investigated on the anaesthetized dog by programmed electrical stimulation of the heart and simultaneous recording of the His bundle electrogram and monophasic action potentials from the auricular and ventricular endocardial wall. Butoprozine injected intravenously depressed sino-atrial node function, lengthened A-V nodal conduction time and the A-V nodal refractory period, and prolonged the atrial refractory period. Thus butoprozine acted preferentially on parts of the myocardial tissue where the slow inward current seems to be particularly involved. In this respect, butoprozine was more active than amiodarone, but in contrast to this drug, butoprozine did neither prolong the ventricular monophasic action potential duration nor the ventricular refractory period. In the anaesthetized dog both drugs have practically analogous actions except at the ventricular level, which suggests that their effect on ionic currents at this level may be different.