Mexiletine Side Effects

It is possible that some side effects of mexiletine may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to mexiletine: oral capsule, oral capsule extended release

Along with its needed effects, mexiletine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur while taking mexiletine:

Less common
  • Chest pain
  • fast or irregular heartbeat
  • shortness of breath
  • Convulsions (seizures)
  • fever or chills
  • unusual bleeding or bruising

Some side effects of mexiletine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
  • Dizziness or lightheadedness
  • heartburn
  • nausea and vomiting
  • nervousness
  • trembling or shaking of the hands
  • unsteadiness or difficulty in walking
Less common
  • Blurred vision
  • confusion
  • constipation or diarrhea
  • headache
  • numbness or tingling of fingers and toes
  • ringing in the ears
  • skin rash
  • slurred speech
  • trouble in sleeping
  • unusual tiredness or weakness

For Healthcare Professionals

Applies to mexiletine: oral capsule


Generally, mexiletine has been well tolerated. Side effects usually have been reversible and dose-related. The most common side effects associated with mexiletine therapy have been gastrointestinal and nervous system effects. The incidence of side effects increases at serum levels greater than 2.0 mcg/mL.


A case of mexiletine esophageal ulceration has been reported. Mexiletine was continued following a dosage reduction and an increase in the dosing interval.

Gastrointestinal side effects have occurred most frequently. Nausea, anorexia, constipation and dyspepsia have been reported in 10% to 40% of patients, primarily during the first 3 to 4 weeks of therapy. Administration with food usually reduced gastrointestinal side effects. Diarrhea was reported in 7% of patients. Dysphagia, salivary changes, altered taste, changes in oral mucosa, hiccups, peptic ulcer disease, upper GI bleeding, and esophageal ulceration have been reported rarely.

Nervous system

Nervous system side effects have included fine hand tremor (10%), dizziness (up to 25%), and difficulties with coordination (10.2%). These symptoms may be the first signs of toxicity. Ataxia, dysarthria, drowsiness, paresthesias, nervousness, speech difficulties, depression, and confusion have been reported less frequently. Short-term memory loss, malaise, seizures, and loss of consciousness have occurred.


Rare cases of torsades de pointes have been associated with mexiletine. New or worsened congestive heart failure has been reported in 1% to 3% of patients.

A case of new first-degree AV heart block and left bundle branch block associated with elevated mexiletine serum levels (34 mcg/mL) was reported.

Cardiovascular symptoms of palpitation and chest pain have occurred in up to 7.5% of patients. A proarrhythmic effect has been reported in approximately 10% of patients and angina 1.7%. Mexiletine has little effect on cardiac contractility. Syncope, hypotension, hypertension, bradycardia, conduction disturbances, atrial arrhythmias, edema, and congestive heart failure have occurred.


Hematologic side effects are rare and have included reports of thrombocytopenia, which is thought to be due to an IgM cold agglutinin.


A generalized pruritic, erythematous, papular rash has been reported in a 77-year-old man.

Hypersensitivity rashes have been reported rarely.


Hepatic side effects have been rare. Isolated cases of mild reversible elevations in liver function tests which resolved after two to three weeks after stopping mexiletine have occurred. Rare cases of severe hepatitis or acute hepatic necrosis have been reported.


Respiratory abnormalities including dyspnea have occurred in 3.7% to 5.7% of patients.

A case of fatal diffuse interstitial pulmonary fibrosis has been associated with mexiletine in a 75-year-old man who had previously taken procainamide and disopyramide. Symptoms of dyspnea preceded chest X-ray abnormalities by months. The diagnosis was made following pulmonary function tests, chest CT scan, and an open lung biopsy.


Ocular side effects including diplopia, nystagmus, and blurred vision have been reported in up to 7.5% of patients.


Dermatologic side effects have been uncommon, however, rash has been reported in up to 4.2% of patients. Rare cases of exfoliative dermatitis and Stevens-Johnson Syndrome have occurred. Diaphoresis, hot flashes, and dry skin have been reported.


Genitourinary side effects including urinary hesitancy and retention have occurred rarely. Impotence and decreased libido have been reported.


Psychiatric side effects including psychosis and hallucinations have been reported.

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