Efficacy of and adverse effects of disopyramide. Comparison of capsules, controlled release tablets and placebo in patients with chronic ventricular arrhythmias.

The efficacy of disopyramide compared to placebo for exercise induced ventricular arrhythmias was tested in a double-blind randomized controlled clinical trial with cross-over design in 14 patients with coronary heart disease. Disopyramide was given as ordinary capsules (q.i.d.) or as a slow release preparation (b.i.d.) in a total dose of 600 mg per day. The placebo preparations were identical looking capsules and tablets. Each treatment period lasted one week. Efficacy was assessed by a standardized exercise test on a bicycle ergometer and a 6-h Holter monitoring at the end of each period. Plasma levels of disopyramide, measured in conjunction with exercise test, fell within therapeutic range, with a mean value of 7.9 and 8.9 mumol/l for capsules and slow release tablets, respectively. Disopyramide gave a marked and significant reduction of ventricular ectopic beats both at rest and during and after exercise. There was also a significant decrease in the number of ectopic beats recorded on tape during treatment periods compared to during placebo periods. There were no differences between the two preparations with respect to antiarrhythmic effect. Only mild side-effects, mainly mild anticholinergic symptoms, similar for both preparations were reported. No significant cardiovascular changes (heart rate and blood pressure response) were observed.