International Mexiletine and Placebo Antiarrhythmic Coronary Trial (IMPACT): II. Results from 24-hour electrocardiograms

The sustained release form of mexiletine (Mexitil–Perlongets), 360 mg b.i.d., was evaluated for antiarrhythmic efficacy in a double-blind placebo trial in 630 patients with recent documented myocardial infarction. The drug was effective in reducing the occurrence of complex forms of ventricular arrhythmias as well as frequent premature ventricular complexes during the first four months of treatment. In addition, a favourable trend antiarrhythmic efficacy of the drug was observed after 12 months of treatment, but this was not statistically significant. The data from this study suggest that mexiletine was as effective in preventing the occurrence of frequent or complex cardiac arrhythmias as in reducing such arrhythmias present during the first four months following acute myocardial infarction. Mortality was higher in the mexiletine group (7.6%) than in the placebo group (4.8%), although the difference was not statistically significant.