Prophylactic use of mexiletine in the elderly with acute myocardial infarction.

A double blind randomised study comparing the effects of oral mexiletine and placebo given to elderly patients (65 years and older) immediately following hospital admission with suspected myocardial infarction (MI) is described. The study comprised one hundred and fifty-four patients of which 74 had confirmed myocardial infarction according to the diagnostic criteria of the study. Eighty patients without definite evidence of myocardial infarction were subsequently excluded from the study. Thirty-three patients (44.5%) with confirmed MI treated with mexiletine, compared with 41 (51%) in the placebo group showed no significant difference in mortality at 48 hours and 14 days. The mexiletine treated group showed a significant reduction (p less than 0.05) in certain forms of ventricular dysrhythmias. Six of these patients (18%) taking mexiletine had the drug withdrawn because of possible adverse drug reactions compared with two (4.8%) of the placebo group. None of the patients withdrawn because of possible adverse drug reactions had any long term side effect. Mild confusion observed in one patient was reversed after withdrawal of therapy. Results of this study indicate the safety of mexiletine as an anti-arrhythmic drug and its efficacy in suppression of certain ventricular dysrhythmias in the elderly with acute myocardial infarction. The overall mortality rate in both groups (mexiletine and placebo) remained unchanged.