Mexiletine HCl

A to Z Drug Facts

 Action Reduces rate of rise of action potential; decreases effective refractory period in Purkinje fibers; has local anesthetic actions.

 Indications Treatment of documented life-threatening ventricular arrhythmias such as sustained ventricular arrhythmias. Unlabeled use(s): Prevention of ventricular arrhythmias in acute phase of MI; reduction of pain, dysesthesia and paresthesia associated with diabetic neuropathy.

 Contraindications Preexisting second-or third-degree atrioventricular block (if pacemaker is not present); cardiogenic shock.

 Route/Dosage

Ventricular Arrhythmias

ADULTS: PO 200 mg q 8 hr initially, increasing up to 400 mg q 8 hr if necessary maximum 1200 mg/day). Adjust dose by 50–100 mg increments q 2–3 days. For rapid control of ventricular arrhythmias, give loading dose of 400 mg followed by 200 mg in 8 hr. With dose £ 300 mg q 8 hr, may give total daily dose q 12 hr (maximum 450 mg q 12 hr).

 Interactions

Aluminum-magnesium hydroxide, atropine, narcotics: May slow absorption. Cimetidine: May increase or decrease mexiletine plasma levels. Hydantoins, rifampin: May increase mexiletine clearance. Metoclorpramide: May accelerate absorption. Theophylline: May increase serum theophylline levels.

 Lab Test Interferences May result in abnormal liver function tests, positive ANA titer or thrombocytopenia.

 Adverse Reactions

CV: Palpitations; chest pain; increased ventricular arrhythmias or premature ventricular contractions; angina or angina-like pain; CHF. CNS: Dizziness; lightheadedness; tremor; nervousness; coordination difficulties; hanges in sleep habits; headache; paresthesias or numbness; weakness; fatigue; peech difficulties; confusion; depression. EENT: Blurred vision; tinnitus. GI: Nausea; constipation; abdominal pain; vomiting; diarrhea; anorexia; heartburn; ry mouth; changes in appetite. HEPA: Hepatitis; hepatic necrosis. RESP: Shortness of breath. OTHER: Fever; rash; nonspecific edema; arthralgias.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk. Children: Safety and efficacy not established. Cardiovascular effects: Has proarrhythmic effect; therapy should be initiated in hospital. Convulsions: Have occurred; use drug with caution in patients with known seizure disorder. Hepatic impairment: Use drug with caution in patients with hepatic impairment. Reduce dosage in patients with severe liver disease. Urinary pH: Marked alterations in urinary pH may alter mexiletine elimination; avoid drugs or diets that alter pH.

 Administration/Storage

• Administer with food or antacids to reduce GI distress.
• When transferring from lidocaine, stop lidocaine when first oral dose is administered.
• Store at room temperature.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note history of blood dyscrasias and second- or third-degree heart block without pacemaker.
• Maintain IV during conversion from lidocaine until suppression of arrhythmia appears satisfactory.
• Perform continuous ECG monitoring. Evaluate when desired antiarrhythmic effect has been obtained.
• Monitor BP continuously throughout therapy.
• Monitor I&O.
• Monitor drug serum levels to evaluate for toxic or subtherapeutic dosage regimens.
• Monitor serum electrolytes and liver enzymes periodically throughout therapy.
• If worsening of arrhythmia or CNS symptoms occurs, notify physician.

 Patient/Family Education

• Instruct patient to take medication with food or antacid.
• Teach patient to monitor pulse rate. Advise patient to notify physician if pulse rate is < 50 bpm or becomes irregular.
• Explain that medication may cause dizziness and lightheadedness. Caution patient to take appropriate safety precautions.
• Remind patient to carry identification describing cardiac disease and medication regimen.
• Instruct patient to report these symptoms to physician: unexplained general tiredness, jaundice, fever, sore throat, bruising or bleeding.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts