What is this medication?
Antiarrhythmic Agent, Class Ib
Mexiletine is indicated for treatment of ventricular arrhythmias.
“Alert: US Warning
The use of mexiletine as well as other antiarrhythmic agents should be reserved for patients with life-threatening ventricular arrhythmias only. Abnormal liver function tests have been reported, some in the first few weeks of therapy with mexiletine. Most of these have been observed in the setting of congestive heart failure or ischemia and their relationship to mexiletine has not been established."
How does this medication work?
Mexiletine is a Class IB antiarrhythmic that blocks sodium channels in cardiac myocytes and nerve cells reducing the rate of depolarization and increasing the effective refractory period/action potential duration ratio.
How should I take this medication?
Usual (Oral): Initial: 150 to 200 mg every 8 to 12 hours (may load with 400 mg if necessary); adjust dose as needed in 50 or 100 mg increments no more frequently than every 2 to 3 days up to 300 mg every 8 to 12 hours; usual dose: 150 to 300 mg every 8 to 12 hours (AHA/ACC/HRS [Al-Khatib 2017]); maximum dose: 1.2 g/day.
How to Use: Take with food. Try to take around the clock rather than 3 times daily to promote less variation in peak and trough serum levels.
What should I watch for while using this medication?
Before using mexiletine make sure your physician is aware of any allergies or medications you currently take, pre-existing medical conditions and activities you perform. Dyscrasia including leukopenia, agranulocytosis and thrombocytopenia have been reported with the use of mexiletine. Mexiletine can cause drug reactions with eosinophilia and systemic symptoms which include eosinophilia, fever, rash, and/or lymphadenopathy in association with other organ involvement, such as hepatitis, nephritis, hematologic abnormalities, myocarditis, or myositis, sometimes resembling an acute viral infection. Abnormal liver function tests have been reported within the first few weeks of using mexiletine. Proarrhythmia may occur with the use of mexiletine especially in those with life-threatening arrhythmias. Mexiletine should be used with caution in patients with conduction disturbances, electrolyte disturbances, heart failure, and seizure disorders.
What if I miss a dose?
If you miss a dose of medication, try to take it as soon as possible. However, if it is almost time for your next dose, take only that scheduled dose. Do not take double or extra doses.
How should I store this medication?
Keep out of the reach of children at all times. Store at room temperature, 59 to 86° F (15 to 30° C). Protect from light. Keep the container tightly closed. Properly dispose of any unused medication after the expiration date.
What are the possible side effects of using this medication?
Palpitations, chest pain, angina, dizziness/light-headedness, tremor, coordination difficulties, changes in sleep habits, weakness, nervousness, fatigue, speech difficulties, confusion/clouded sensorium, paresthesias/numbness, tinnitus, depression, nausea/vomiting/heartburn, diarrhea, constipation, changes in appetite, blurred vision/visual disturbances, headache, rash, dyspnea/respiratory, dry mouth, arthralgia, fever
Note this is not a complete list of side effects, only the most common.
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