Mexiletine Side Effects

Some side effects of mexiletine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to mexiletine: oral capsule

If you experience any of the following serious side effects, stop taking mexiletine and seek emergency medical attention:

• an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);

• a new or a worsening irregular heartbeat pattern;

• wheezing, coughing, chest pain, or chest discomfort;

• unusual bruising or bleeding; or

• fever, sore throat, a sore mouth, mouth ulcers, or an infection.

Other, less serious side effects may be more likely to occur. Continue to take mexiletine and talk to your doctor if you experience

• dizziness, lightheadedness, or tiredness;

• poor coordination;

• dry mouth;

• upset stomach, heartburn, vomiting, or decreased appetite;

• diarrhea or constipation;

• headache or blurred vision;

• weakness;

• numbness, tingling, or tremor (shaking);

• ringing in your ears;

• a rash; or

• depression.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to mexiletine: oral capsule

General

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.

Gastrointestinal

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.

Cardiovascular

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

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

Hypersensitivity

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

Hypersensitivity rashes have been reported rarely.

Hepatic

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

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

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

Dermatologic

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

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

Psychiatric

Psychiatric side effects including psychosis and hallucinations have been reported.

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