Antiarrhythmic efficacy of combined intravenous and oral mexiletine in acute myocardial infarction. A double blind placebo-controlled study.

The antiarrhythmic efficacy of mexiletine in acute myocardial infarction (AMI) was studied in 99 patients randomized to mexiletine or placebo treatment. The loading dose was 250 mg i.v. and 400 mg orally followed by 200 mg orally 2 h later, and thereafter 200 mg t.i.d. up to 42 h. Arrhythmias occurring during 48 h were analysed from continuous electrocardiographic recordings. AMI was verified in 35 of 50 mexiletine patients and in 38 of 49 placebo patients. No deaths or instances of ventricular fibrillation occurred in the AMI patients. The number of patients who had any event of accelerated idioventricular rhythm (AIVR; <0.05), runs of ventricular premature beats (VPBs; <0.01), ventricular tachycardia (<0.01) and Ron T beats (<0.05) was smaller in the mexiletine group than in the placebo group. The number of all VPBs (<0.05), hours with occurrence of AIVR (<0.05), runs (<0.01) and Ron T beats (<0.05) was smaller in the mexiletine than in the placebo group. Serum levels of mexiletine tended to be low throughout the study. The half-life of the elimination was 13.7±7.2 h (means±S.D.). Adverse effects were infrequent, and the treatment was well-tolerated. Combined iv. and oral mexiletine prophylaxis significantly suppressed repetitive ventricular tachyarrhythmias and RonT beats. However, no clinical benefit from mexiletine treatment could be shown in a coronary care unit with a low frequency of primary ventricular fibrillation. [ABSTRACT FROM PUBLISHER]