Comparative effect of disopyramide and ethmozine in suppressing complex ventricular arrhythmias by use of a double-blind, placebo-controlled, longitudinal crossover design.

This placebo-controlled, double-blind, longitudinal crossover study compares the efficacy of disopyramide and ethmozine, a new investigational drug, in suppressing frequent (40 or more per hour) ventricular premature depolarizations (VPDs) in 27 patients completing a 37 day protocol. Although both drugs significantly reduced VPDs relative to placebo, ethmozine was a superior antiarrhythmic drug in ach9eving near-total abolition of VPDs (30% of patients), which was never observed during disopyramide dosing (p less than .05). At the 80% VPD reduction level, ethmozine was effective in 56% of all patients compared with an effectiveness in only 22% of patients during disopyramide therapy (p less than .05). The mean peak plasma level of ethmozine was 0.66 +/- 0.8 micrograms/ml, which significantly fell to a trough level of 0.1 +/- 0.08 micrograms/ml (p less than .001). Mean peak and trough plasma levels of disopyramide exhibited less fluctuation (2.6 +/- 0.9 micrograms/ml vs 2.2 +/- 0.9 micrograms/ml). Ethmozine had no effect on the QT interval, whereas disopyramide prolonged it significantly. Importantly, while disopyramide produced serious side effects in 30% of patients, ethmozine was well tolerated with no statistically significant side effects compared with placebo.