Reviewed on 4/1/2022

What Is Mexiletine and How Does It Work?

Mexiletine is a prescription medicine used to treat the symptoms of irregular heartbeats (ventricular tachycardia).

  • Mexiletine is available under the following different brand names: Mexitil

What Are Dosages of Mexiletine?

Adult dosage


  • 150mg
  • 200mg
  • 250mg

Ventricular Arrhythmias (Life-Threatening)

Adult dosage

  • Initial: 200 mg orally every 8 hours; may load with 400 mg followed by 200 mg orally every 8 hours if necessary for rapid control of the ventricular arrhythmia
  • Dose range: 200-300 mg orally every 8 hours
  • May increase to 400 mg every 8 hours; not to exceed 1200 mg/day
  • Take with food or antacid
  • Therapeutic range: 0.5-2 mg/L
  • Pediatric dosage
  • Not FDA approved
  • The usual dose for arrhythmias: 2.5-5 mg/kg orally every 8 hours

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Are Side Effects Associated with Using Mexiletine?

Common side effects of Mexiletine include:

Serious side effects of Mexiletine include:

  • hives,
  • difficulty breathing,
  • swelling of the face, lips, tongue, or throat,
  • abnormal liver function tests,
  • chest pain,
  • new or a worsening irregular heartbeats pattern, and
  • liver problems--nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, and jaundice (yellowing of the skin or eyes).

Rare side effects of Mexiletine include:

  • none 

This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.


In the U.S., 1 in every 4 deaths is caused by heart disease. See Answer

What Other Drugs Interact with Mexiletine?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns.

What Are Warnings and Precautions for Mexiletine?


  • Hypersensitivity to mexiletine
  • Cardiogenic shock, preexisting second- or third-degree AV block without pacemaker

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Mexiletine?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Mexiletine?”


  • Use caution in CHF, hypotension, history of seizures
  • Monitor and adjust the dose to prevent QTc prolongation
  • Patients with second or third-degree heart block may be treated if continuously monitored; use caution when used in such patients or patients with pre-existing sinus node dysfunction or intraventricular conduction abnormalities
  • Use in less severe arrhythmias not recommended; avoid in treatment of asymptomatic ventricular premature contractions or conduction disturbances
  • Some abnormal liver function tests reported in the first few weeks of therapy; most have been observed in settings of congestive heart failure or ischemia; patients with liver disease should be followed carefully while receiving therapy; caution should also be observed in patients with hepatic dysfunction secondary to congestive heart failure
  • Rare instances of severe liver injury, including hepatic necrosis, reported in association with treatment; recommended that patients in whom an abnormal liver test has occurred, or who have signs or symptoms suggesting liver dysfunction, be carefully evaluated; if the persistent or worsening elevation of hepatic enzymes is detected, consider discontinuing therapy
  • Before use electrolyte imbalances (especially hypokalemia or hypomagnesemia) must be corrected
  • Avoid concurrent drug therapy or dietary regimens which may markedly alter urinary pH during therapy; the minor fluctuations in urinary pH associated with normal diet do not affect the excretion of the drug
  • Marked leukopenia, agranulocytosis, and mild depressions of leukocytes and thrombocytopenia reported (rare); If significant hematologic changes are observed, the patient should be carefully evaluated, and, if warranted, therapy should be discontinued; blood counts usually return to normal within one month of discontinuation

Pregnancy and Lactation

  • Use with caution if the benefits outweigh the risks during pregnancy.
  • Lactation
    • Enters breast milk at concentrations comparable to maternal plasma (AAP Committee states compatible w/ nursing) 


Heart Disease: Symptoms, Signs, and Causes See Slideshow
Medscape. Mexiletine.

Health Solutions From Our Sponsors