Electrophysiologic and hemodynamic effects of bethanidine sulfate on the immature mammalian heart

The cumulative electrophysiologic and hemodynamic effects of bethanidine sulfate (2.5, 5, 10 and 15 mg/kg i.v.) were studied in 9 canine neonates and 7 adult dogs. Increased heart rate, blood pressure and enhanced atrioventricular nodal function, observed in both groups, and decreased ventricular refractory periods and inducibility of ventricular arrhythmias seen in the adult, are probably related to a bethanidine-mediated release of catecholamines. However, in spite of the catecholamine release, bethanidine sulfate results in a significant prolongation of atrial refractoriness, this effect being quantitatively more important in the neonate than in the adult.