Mexiletine, a new antiarrhythmic agent, for treatment of premature ventricular complexes.

This double-blind crossover study was designed to compare the safety and efficacy or mexiletine, a new class I antiarrhythmic agent, with those of a placebo in reducing premature ventricular complexes. Twelve patients who had a median of 294 such complexes/hour were admitted to the study. Eleven completed 4 weeks of trial with mexiletine and placebo with ambulatory electrocardiographic (Holter) recordings taken at the end of each treatment period. The doses given were designed to reduce the frequency of premature ventricular complexes by 50 percent or more from the baseline value. Mexiletine significantly reduced the rate of premature ventricular complexes by comparison with placebo (-66 percent versus 3 percent, p = 0.032). In addition, mexiletine reduced the median number/hour of ventricular couplets observed. After 4 weeks of therapy, 2, 2, 1 and 6 patients, respectively, were taking 100, 200, 300 and 400 mg of mexiletine every 8 hours. Mexiletine produced no significant change in baseline values including electrocardiographic intervals, blood pressure or heart rate. The most frequently observed adverse effects were digestive difficulties (eight patients taking mexiletine, four taking placebo) and central nervous system effects (seven taking mexiletine, five taking placebo). These data show the efficacy and safety of mexiletine in the treatment of premature ventricular complexes in a majority of patients.