Acute Effects of Intravenous Prifuroline and Amiodarone on Canine Cardiac Automaticity, Conduction, and Refractoriness

We compared the acute electrophysiologic properties of prifuroline (P), a new aminopyrroline derivative, to those of amiodarone (A) in pentobarbital-anesthetized dogs using His bundle recordings and programmed stimulation. Ten dogs received in randomized order four cumulative doses of P (2.5-20 mg/kg) and of A (1.25-10 mg/kg) with a 14-day interval between drug administrations. In a control group of four dogs receiving the diluent of the drugs, no significant changes occurred in cardiac automaticity, conduction, and refractoriness except for the atrioventricular (AV) nodal functional refractory period (RP), which increased with time (p less than 0.05). P and A produced a significant dose-related decrease in heart rate and in sinus node recovery time, with A being 3.7-3.1 times more potent than P. While atrionodal conduction time increased with both drugs, only P resulted in a significant dose-related increase in the His-Purkinje system conduction time. Prifuroline was 2.9 times more potent than A in increasing the atrial effective refractory period, while A was 2.5 times more potent than P in increasing the ventricular effective refractory period. Both drugs increased the AV nodal refractoriness in a dose-dependent way. These results suggest that the new compound prifuroline possesses some properties similar to intravenous amiodarone on sinus automaticity, atrionodal conduction, and atrial and ventricular refractoriness. However, its effects on the His-Purkinje System are typical of those of a class I quinidine-like agent.