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Mexiletine

Brands and Forms

  • Mexitil
    • capsule: 150mg, 200mg, 250mg

Uses of Mexiletine

Mexiletine is used most commonly in general medicine to treat heart arrhythmias. In psychiatry, it can be used for treatment-resistant cases of Manic and Mixed Episodes in Bipolar Disorder.

How Mexiletine Works

Mexiletine is an antiarrhythmic medication.

Cautions when Using Mexiletine

Mexiletine should not be used in patients with 2nd and 3rd degree AV block (a type of heart conduction problem) who do not have pacemakers. It should also be avoided in cardiogenic shock.

Dosing of Mexiletine

The initial dose is 200mg every 8 hours, and it can be increased by 50-100mg each dose as quickly as every 3 days, to a maximum of 400mg every 8 hours (1200mg/day). Doses of 900mg/day or less can also be given in two daily doses 12 hours apart. Usually this is done only once an effective dose is established.

Onset of action

It may take a couple of weeks for the symptoms of a Manic or Mixed Episode to show a response to the medication.

Kidney impairment

Lower dose in individuals with severe kidney impairment.

Liver impairment

Lower dose in individuals with severe liver impairment.

Side-effects of Mexiletine

Below is a list of most of the reported side-effects of Mexiletine. Most of these side-effects occur in only a minority of individuals, and many also resolve with time while the medication is continued.

Cardiovascular: palpitations; chest pain; increased ventricular arrhythmias; angina; exacerbation of congestive heart failure (rare).

Central Nervous System: dizziness; lightheadedness; tremor; incoordination; headache; changes in sleep pattern; weakness; paresthesias; fatigue; speech difficulties; confusion; clouded consciousness; drowsiness; unsteadiness.

Dermatologic: rash

Eyes, Ears, Nose and Throat: blurred vision; visual disturbances; tinnitus; nystagmus.

Gastrointestinal: nausea; vomiting; heartburn; diarrhea; constipation; changes in appetite; dry mouth; abdominal pain; dyspepsia.

Hematologic: blood dyscrasias.

Musculoskeletal: arthralgia; myelofibrosis.

Respiratory: shortness of breath.

Psychiatric: anxiety; depressed mood.

Common side-effects of Mexiletine

Nausea, vomiting, heartburn, dizziness, lightheadedness, tremor, incoordination, headache, changes in sleep pattern, palpitations, chest pain.

Rare but serious side-effects of Mexiletine

Ventricular arrhythmias and worsening of congestive heart failure.

Mexiletine overdose

Dizziness, drowsiness, nausea, hypotension, sinus bradycardia, paresthesia, seizures, confusion, bundle branch block, AV heart block, asystole, ventricular tachyarrhythmias including ventricular fibrillation, respiratory arrest, coma.

Mexiletine and pregnancy

Category C: some animal studies show adverse effects at very high doses, but no controlled human studies have been done; should only be used in pregnancy if clearly needed and if benefits outweigh potential risks.

Medical Monitoring for Mexiletine

An electrocardiogram should be obtained prior to starting the medication, and then a few days after reaching a steady dose.

Drug Interactions with Mexiletine

  • Mexiletine blood concentrations can be increased by caffeine, Cimetidine, Fluvoxamine, and Propafenone.
  • Mexiletine blood concentrations can be decreased by Cimetidine, hydantoins, Rifampin, and Phenobarbital.
  • Mexiletine can increase Theophylline blood concentrations.