[Electrophysiologic and anti-arrhythmia properties of propafenone deducible from experimental studies in vitro]

The aim of our study was to analyze which of the basic "in vitro" properties of Propafenon could be relevant to the antiarrhythmic action, as well as to contribute to its classification among the antiarrhythmic drugs. Propafenon belongs to class 1 of Singh and Hauswirth's classification and its characteristics are similar to those of lidocaine; Propafenon may act mainly on ventricular arrhythmias caused by a reentry circuit or by increased automaticity including those which occur in the post-ischemic state and those due to digitalis toxicity. A peculiar aspect of Propafenon seems, however, to be the beta-receptor blocking activity (especially beta-2) shown at therapeutical doses. Such property can induce a depression of heart rate and contractility mainly in patients with a compensatory increase of the sympathetic tone. On the contrary, the calcium-antagonist action of Propafenon is very weak, as it is detected only at doses 80-100 times higher than those that exert an electrophysiologic action. It is also possible that the pharmacological activity of the drug "in vivo" can assume aspects different from those expected from "in vitro" experiments, because of the various metabolites of Propafenon demonstrated in human beings.