Mexiletine in treatment of ventricular arrhythmias. A long-term follow-up

Effectiveness and safety of mexiletine in patients at risk for (recurrent) ventricular arrhythmias: a systematic review

While mexiletine has been used for over 40 years for prevention of (recurrent) ventricular arrhythmias and for myotonia, patient access has recently been critically endangered. Here we aim to demonstrate the effectiveness and safety of mexiletine in the treatment of patients with (recurrent) ventricular arrhythmias, emphasizing the absolute necessity of its accessibility. Studies were included in this systematic review (PROSPERO, CRD42020213434) if the efficacy or safety of mexiletine in any dose was evaluated in patients at risk for (recurrent) ventricular arrhythmias with or without comparison with alternative treatments (e.g. placebo). A systematic search was performed in Ovid MEDLINE, Embase, and in the clinical trial registry databases ClinicalTrials.gov and ICTRP. Risk of bias were assessed and tailored to the different study designs. Large heterogeneity in study designs and outcome measures prompted a narrative synthesis approach. In total, 221 studies were included reporting on 8970 patients treated with mexiletine. Age ranged from 0 to 88 years. A decrease in ventricular arrhythmias of >50% was observed in 72% of the studies for pre-mature ventricular complexes, 64% for ventricular tachycardia, and 33% for ventricular fibrillation. Electrocardiographic effects of mexiletine were small; only in a subset of patients with primary arrhythmia syndromes, a relative (desired) QTc decrease was reproducibly observed. As for adverse events, gastrointestinal complaints were most frequently observed (33% of the patients). In this systematic review, we present all the currently available knowledge of mexiletine in patients at risk for (recurrent) ventricular arrhythmias and show that mexiletine is both effective and safe.

Long-term clinical experience with mexiletine

Mexiletine was given to 12 patients for different periods of time varying from 4 to 96 months, with a mean of 47.8 months. At the latest follow-up in August 1983, five patients had been taking mexiletine for 74 to 96 months (mean 85 months). Mexiletine was well tolerated and serious side effects were not seen. In particular, there was no rise in antinuclear factor titer. The serum level of mexiletine was easily maintained within the therapeutic range, and most side effects correlated closely with the drug level. It is concluded that mexiletine can be administered for a long time as a safe alternative to other antiarrhythmic drugs.

Comparison of newer antiarrhythmic agents

In the past decade a number of new antiarrhythmic drugs ahve been introduced. They have been extensively used in the acute phase of myocardial infarction. Few, if any, long-term comparative trials of these newer agents have been reported. Most of these newer agents have been shown to be able to reduce the frequency of ventricular arrhythmias but not the mortality rate. Beta blockers and some antiplatelet adhesive drugs, however, have reduced the mortality rate following myocardial infarction. There is a need for long-term properly stratified trials of these effective agents.