Hemodynamic, electrocardiographic and toxic effects of the intravenous administration of increasing doses of mexiletine in the dog. Comparison with similar effects produced by other antiarrhythmics.

The hemodynamic and electrocardiographic effects of intravenous injections of mexiletine in progressively increased doses, starting from 1.5 and 3 mg, have been studied in two series of 8 and 6 dogs anaesthetized with pentobarbital. The analysis of the results showed that absence of change in aortic pressure, heart rate and output when the minimal doses are injected, is due to the interaction of opposite effects: a direct depressing effect on the myocardial contractility, and a sympathic reflex stimulation secondary to a peripheral vasodilation. The comparison of hemodynamic, electrocardiographic and toxic effects of mexiletine with those produced by other antiarrhythmics showed that mexiletine placed itself among the better tolerated antiarrhythmics during the administration of progressively increasing doses.