Mexiletine: Its Role in the Management of Chronic Ventricular Arrhythmias

Abstract

Mexiletine is a class IB anti arrhythmic agent structurally similar to lidocaine but with the advantage of a high bioavailability and relatively long half‐life, making it useful for long‐term oral therapy of ventricular arrhythmias. Mexiletine can be used orally or intravenously. Orally, it has a high bioavailability, reaching peak plasma concentration between 2 and 4 hours after administration. The steady‐state therapeutic plasma concentration ranges from 0.5 to 2.5 fig/ml. These levels are obtained by doses of 200–300 mg every 6–8 hours. It is mostly metabolized by the liver and its metabolism and excretion are not significantly affected by renal failure. Mexiletine has very few deleterious drug interactions; more importantly, it does not affect digoxin blood levels. Its efficacy in controlling ventricular arrhythmias has been widely studied. The reported success rate varies from 84% to 52%. In our study of patients with symptomatic and refractory ventricular arrhythmias, the success rate with mexiletine was 55% initially and 33% at one year. Mexiletine appears to be most useful in combination with other anti arrhythmic agents such as propranolol, quinidine, procainamide, or amiodarone. Mexiletine has very few cardiac side effects. It was found not to have significant negative inotropic effects even in patients with congestive heart failure. Its major side effects, however, include gastric intolerance. Other less common side effects include central nervous system manifestations. Like all other antiarrhythmics, it can potentially aggravate ventricular arrhythmias in about 10% of patients but in most cases the proarrhythmic effect is not Clin cally significant.