Ethacizin: a new efficacious Soviet antiarrhythmic drug of the phenothiazine group.

Ethacizin, a new Soviet antiarrhythmic agent of the phenothiazine group, was tested on 82 patients with ventricular rhythm disturbances. Antiarrhythmic effects of the drug were assessed by means of ambulatory ECG monitoring. The investigation protocol included acute drug testing with 50 mg, 100 mg, and 150 mg, and short-term maintenance therapy with 150 to 300 mg/24 hours of ethacizin (mean 183 +/- 46 mg/24 hours) for 3 to 14 days (mean 7 +/- 3 days). Ethacizin reduced the total number of ventricular premature beats (VPBs) from 17,263/24 hours (on placebo) to 3458/24 hours (p less than 0.001) and suppressed couplets and ventricular tachycardia (VT) runs by 90% in 94% and 96% of patients, respectively. Maximum blood plasma concentration of ethacizin was observed in 110 to 120 minutes and accounted for 300 to 447 ng/ml (mean 354 +/- 77 ng/ml), with a minimum therapeutic drug plasma concentration ranging from 29 to 101 ng/ml (mean 73 +/- 27 ng/ml). There was a significant increase in PQ and QRS intervals with ethacizin. Ethacizin was well tolerated. Thus ethacizin had high antiarrhythmic efficacy in patients with VPBs and no significant side effects.