Last reviewed 2026-04-20 · How we verify

MEXILETINE HYDROCHLORIDE

Mexiletine, an oral antiarrhythmic, reduces ventricular arrhythmias by inhibiting sodium currents and altering refractory periods.

Mexiletine Hydrochloride is an orally administered antiarrhythmic drug currently on the market, primarily indicated for the treatment of ventricular arrhythmias. Its key strength lies in its mechanism of action, which effectively reduces ventricular arrhythmias by inhibiting sodium currents and altering refractory periods. The primary risk to consider is the key composition patent expiry in 2028, which could lead to increased competition from generic versions.

At a glance

Mechanism of action

Mexiletine works by blocking sodium channels in heart cells, which helps to stabilize the electrical activity of the heart. This reduces the risk of abnormal heart rhythms, particularly those that can be life-threatening.

Approved indications

• Ventricular Arrhythmias

Boxed warnings

• BOXED WARNING 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 reserved for patients with life-threatening ventricular arrhythmia. Acute Liver Injury In postmarketing 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 hydrochloride has not been established.

Common side effects

• upper gastrointestinal distress
• lightheadedness
• tremor
• coordination difficulties
• palpitations
• chest pain
• increased ventricular arrythmia/PVCs
• nausea/vomiting/heartburn
• dizziness/lightheadedness
• tremor
• nervousness
• coordination difficulties

Drug interactions

• fluvoxamine
• propafenone
• phenytoin, rifampin, phenobarbital
• cimetidine
• theophylline
• magnesium-aluminum hydroxide

Key clinical trials

• The Efficacy and Safety of Once Daily Mexiletine PR in Patients With Myotonic Dystrophy Type 1 and Type 2 (PHASE3)
• An Open-Label Extension Study to Evaluate the Long-Term Safety and Efficacy of Once Daily Mexiletine PR in Patients With Myotonic Dystrophy Type 1 and Type 2 Who Have Completed MEX-DM-302 Study. (PHASE3)
• An Open-Label, Randomized, Cross-Over Study to Investigate the Efficacy and Safety of Mexiletine PR Compared to Mexiletine IR (PHASE3)
• Clinical Trial of Mexiletine Hydrochloride for Spinal and Bulbar Muscular Atrophy (PHASE2, PHASE3)
• Study to Investigate the Efficacy and Safety of Mexiletine in Patients With Myotonic Dystrophy Type 1 and Type 2 (PHASE3)
• A Phase II/III Double-Blind Study of Amitriptyline and Mexiletine for Painful Neuropathy in HIV Infection (PHASE2)
• Patient Assisted Intervention for Neuropathy: Comparison of Treatment in Real Life Situations (PHASE4)
• Clinical Efficacy Trial of Mexiletine for Myotonic Dystrophy Type 1 (PHASE2)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• MEXILETINE HYDROCHLORIDE CI brief — competitive landscape report
• MEXILETINE HYDROCHLORIDE updates RSS · CI watch RSS