What is the correct dosing for flecainide?

Flecainide Dosing Guidelines

The standard dosing for flecainide is 50-100 mg twice daily initially, with a maximum maintenance dose of 150 mg twice daily (300 mg/day) for most patients with supraventricular arrhythmias. 1

Initial Dosing and Titration

• Starting dose: 50 mg every 12 hours for patients with paroxysmal supraventricular tachycardia (PSVT) and paroxysmal atrial fibrillation (PAF) 1
• Titration: Increase in increments of 50 mg twice daily every four days until efficacy is achieved 1
• Maximum recommended dose: 300 mg/day for patients with paroxysmal supraventricular arrhythmias 1
• For sustained ventricular tachycardia (VT), the starting dose is higher at 100 mg every 12 hours, with a maximum of 400 mg/day 1

Special Population Considerations

Renal Impairment

• For severe renal impairment (creatinine clearance ≤35 mL/min):
  • Reduce dose to 100 mg once daily or 50 mg twice daily 2, 1
  • Frequent plasma level monitoring is required 2

Pediatric Dosing

• Under six months of age: approximately 50 mg/m² body surface area daily, divided into 2-3 doses 2, 1
• Over six months of age: initial dose may be increased to 100 mg/m² per day 1
• Maximum recommended dose: 200 mg/m² per day 1

Drug Interactions

• When co-administered with amiodarone, reduce flecainide dose by 50% 2
• Monitor digoxin concentrations when used concomitantly 2

Monitoring Requirements

ECG Monitoring

• Baseline ECG before initiation
• Follow-up ECG after 3-5 days of therapy
• ECG at each dose change and regular intervals thereafter 2
• Discontinue or reduce dose if:
  • QRS duration increases >25% from baseline
  • PR interval increases to ≥0.3 seconds
  • QRS duration exceeds 200 ms 2

Plasma Level Monitoring

• Target trough plasma levels: 0.2-1.0 mcg/mL
• Levels above 0.7-1.0 mcg/mL require close monitoring 2
• In children, the usual therapeutic level is 200-500 ng/mL (up to 800 ng/mL may be required in some cases) 1

Important Contraindications

Flecainide is absolutely contraindicated in:

• Structural heart disease
• Coronary artery disease
• Reduced left ventricular ejection fraction
• Cardiogenic shock
• Sinus or AV conduction disease (without pacemaker)
• Brugada syndrome
• Atrial flutter without concomitant AV nodal blocking therapy 2

Safety Considerations

• Flecainide has a long half-life (12-27 hours), so steady-state plasma levels may not be achieved until 3-5 days of therapy 1
• Proarrhythmic effects are more common in patients with structural heart disease 3
• Common adverse effects include dizziness, visual disturbances, and headaches 3, 4
• More frequent monitoring is needed in elderly patients and those on interacting medications 2

Efficacy Considerations

• Flecainide appears particularly effective for PSVT with 87% of patients showing symptomatic improvement 3
• For PAF, 73% of patients show symptomatic improvement 3
• Higher doses (150 mg twice daily) demonstrate greater efficacy, with 86% of PSVT patients and 61% of PAF patients experiencing no tachycardia recurrence 5

Flecainide's dosing must be carefully managed with appropriate monitoring to balance efficacy against potential risks, particularly in patients with any cardiac abnormalities or renal impairment.