Mexiletine Hydrochloride Capsules are indicated for the treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia, that, in the judgement of the physician, are life-threatening.
Because of the proarrhythmic effects of mexiletine, its use with lesser arrhythmias is generally not recommended.Treatment of patients with asymptomatic ventricular premature contractions should be avoided.Initiation of mexiletine treatment, as with other antiarrhythmic agents used to treat life-threatening arrhythmias, should be carried out in the hospital.Antiarrhythmic drugs have not been shown to enhance survival in patients with ventricular arrhythmias.
Mexiletine hydrochloride is contraindicated in the presence of cardiogenic shock or pre-existing second- or third-degree AV block (if no pacemaker is present). WARNINGS Mortality: In the National Heart, Lung and Blood Institute’s Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multicentered, randomized, double-blind study in patients with asymptomatic non-life-threatening ventricular arrhythmias who had a myocardial infarction more than six days but less than two years previously, an excessive mortality or non-fatal cardiac arrest rate (7.7%) was seen in patients treated with encainide or flecainide compared with that seen in patients assigned to carefully matched placebo-treated groups (3.0%).
The average duration of treatment with encainide or flecainide in this study was ten months. The applicability of the CAST results to other populations (e.g.
those without recent myocardial infarction) is uncertain.
Considering the known proarrhythmic properties of mexiletine and the lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening arrhythmias, the use of mexiletine as well as other antiarrhythmic agents should be reversed for patients with life-threatening ventricular arrhythmia. Acute Liver Injury: In post-marketing experience abnormal liver function tests have been reported, some in the first few weeks of therapy with mexiletine hydrochloride.Most of these have been observed in the setting of congestive heart failure or ischemia and their relationship to mexiletine has not been established.