A trial of prophylactic mexiletine in home coronary care.

A double blind randomised study was undertaken comparing the effects of oral mexiletine and placebo given by general practitioners at home in the early stages of suspected acute myocardial infarction, and continued for six weeks. The study comprised 216 patients. In 59 the diagnosis of acute myocardial infarction was not confirmed. Of the 72 patients with confirmed myocardial infarction treated with mexiletine, 11 (15.3%) died, compared with 19 (22.4%) of the 85 patients given the placebo, and significantly fewer of the former compared with the latter had frequent ventricular ectopics or ventricular tachycardia recorded on 24 hour electrocardiograms. Numbers of patients transferred to hospital or withdrawn from the trial because of arrhythmia or heart failure were similar in the two treated groups. Ten (13.9%) of the patients taking mexiletine had the drug withdrawn because of side effects attributed to it, compared with three (3.5%) of the group taking the placebo. A further five patients (all on mexiletine) also had treatment withdrawn because of side effects but infarction was not later confirmed. The results indicate that oral mexiletine can be given safely to patients with suspected myocardial infarction at home by their general practitioners in the absence of a positive electrocardiographic diagnosis. The frequency of ventricular tachycardia is significantly reduced; but there is no evidence of reduced mortality.