Author + information
- Received May 21, 1985
- Revision received July 9, 1985
- Accepted August 16, 1985
- Published online January 1, 1986.
- Joel Morganroth, MD, FACCa,
- John C. Somberg, MD, FACC,
- Peter E. Pool, MD, FACC,
- Ping-Hwa Hsu, PhD,
- Ian K. Lee, MD, ChB,
- John Durkee, RPh,
- for the Encainide-Quinidine Research Group*
- ↵aAddress for reprints: Joel Morganroth, MD, Likoff Cardiovascular Institute, Hahnemann University Hospital, Broad and Vine Street, Philadelphia, Pennsylvania 19102—1192.
The antiarrhythmic efficacy and safety of oral encainide hydrochloride and quinidine sulfate were compared m a nine center double-blind crossover study in 187 outpatients with benign or potentially lethal ventricular arrhythmias. Patients with at least 30 premature ventricular complexes/h were randomized to receive either encainide, 25 mg four times/day, or quinidine, 200 mg four times/day, for 2 weeks. These doses were continued for another 2 weeks if a 75% or greater reduction in premature ventricular complexes was observed. If this reduction was not seen, encainide was increased to 50 mg four times/day or quinidine to 400 mg four times/day for an additional 2 weeks.
Both drugs produced a statistically significant reduction in premature ventricular complex frequency compared with baseline values. Encainide produced a statistically significant greater mean reduction in total premature ventricular complexes than did quinidine during the initial dose phase and after dose adjustment. More patients required dose increases of quinidine (60%) than of encainide (51 %). Early discontinuation of treatment resulting in advancement to the next study period occurred in 12 patients taking encainide and 38 patients taking quinidine (p < 0.05). PR and QRS intervals increased significantly during encainide treatment, as did QTc and JT intervals during quinidine treatment. No adverse reactions resulted from these electrocardiographic changes.
Adverse reactions were more common with quinidine than with encainide. A proarrhythmic effect was noted in eight patients taking encainide (five had an increase in premature ventricular complex frequency and three an increase in the duration of asymptomatic ventricular tachycardia) and in four patients taking quinidine (one had an increase in premature ventricular complex frequency and two an increase in the duration of asymptomatic ventricular tachycardia; and syncope developed in one) (p = NS). Thus, encainide appears to be more effective and has fewer side effects than quinidine and may be a reasonable alternative to quinidine therapy for ventricular arrhythmias.
- Received May 21, 1985.
- Revision received July 9, 1985.
- Accepted August 16, 1985.
- American College of Cardiology Foundation