Recommended Dosage of Mexiletine
The recommended dosage of mexiletine is 200-300 mg every 8 hours with food or antacid, with a maximum daily dose of 1200 mg. 1
Initial Dosing and Titration
- Start with 200 mg every 8 hours when rapid control of arrhythmia is not essential 1
- Allow a minimum of 2-3 days between dose adjustments, with adjustments made in 50 or 100 mg increments 1
- For rapid control of ventricular arrhythmia, an initial loading dose of 400 mg followed by 200 mg after 8 hours may be administered 1
- Therapeutic effect typically begins within 30 minutes to 2 hours after administration 1
Maintenance Dosing
- Most patients achieve satisfactory control with 200-300 mg given every 8 hours 1, 2
- If satisfactory response is not achieved at 300 mg every 8 hours and the patient tolerates mexiletine well, a dose of 400 mg every 8 hours may be tried 1
- Some patients may be transferred to a 12-hour dosing schedule for convenience, with a maximum of 450 mg every 12 hours 1
Special Populations and Considerations
- Patients with severe liver disease may require lower doses and must be monitored closely 1
- Patients with marked right-sided congestive heart failure may need reduced doses due to decreased hepatic metabolism 1
- Patients with renal failure generally require the usual doses of mexiletine 1
Monitoring and Dose Adjustment
- Clinical and electrocardiographic evaluation (including Holter monitoring if necessary) should be performed to determine the antiarrhythmic effect and guide titration 1
- Monitor for CNS side effects, which increase with total daily dose 1, 2
- Plasma level monitoring may be helpful, particularly when concomitant drugs might affect mexiletine levels 1
Common Adverse Effects
- Gastrointestinal effects (most common): nausea, vomiting 2, 3
- Central nervous system effects: tremor, dizziness, ataxia, paresthesias 2, 3
- Heat intolerance may occur due to mexiletine's effects on sodium channels involved in thermoregulation 4
Clinical Efficacy
- Mexiletine effectively suppresses premature ventricular contractions in 25-79% of patients at doses of 600-900 mg daily 3
- In studies of ambulatory patients with ventricular arrhythmias, mexiletine at 600 mg daily (200 mg every 8 hours) reduced premature ventricular complexes by approximately 64% 5
- For refractory ventricular arrhythmias, mexiletine is effective in 30-50% of patients who have failed other antiarrhythmic drugs 2
Important Precautions
- Adverse effects limit mexiletine use in approximately 20% of patients 2
- Unlike some other antiarrhythmics, mexiletine has minimal effects on hemodynamic variables and cardiac function, making it suitable for patients with left ventricular dysfunction 3
- Mexiletine appears to have a low proarrhythmic potential compared to some other antiarrhythmic agents 3