Flecainide Dosing for Arrhythmias
For supraventricular arrhythmias including atrial fibrillation and PSVT, start flecainide at 50 mg every 12 hours and titrate upward by 50 mg twice daily every 4 days to a maximum of 150 mg every 12 hours (300 mg/day total), while for sustained ventricular tachycardia, initiate at 100 mg every 12 hours with the same titration schedule up to a maximum of 400 mg/day. 1, 2
Standard Maintenance Dosing
Supraventricular Arrhythmias (Atrial Fibrillation, Atrial Flutter, PSVT)
- Initial dose: 50 mg every 12 hours (100 mg/day total) 1, 2
- Titration: Increase by 50 mg twice daily every 4 days until efficacy is achieved 1, 2
- Usual effective range: 50-200 mg every 12 hours 1
- Maximum dose: 150 mg every 12 hours (300 mg/day total) 1, 2
- Most patients achieve adequate control at 100-200 mg twice daily 3, 4
Sustained Ventricular Tachycardia
- Initial dose: 100 mg every 12 hours 2
- Titration: Increase by 50 mg twice daily every 4 days 2
- Usual effective range: Most patients controlled with ≤150 mg every 12 hours 2
- Maximum dose: 200 mg every 12 hours (400 mg/day total) 2
- Critical warning: Must initiate in-hospital with continuous rhythm monitoring due to increased proarrhythmic risk and heart failure, particularly in first few days 2
Acute Cardioversion ("Pill-in-the-Pocket") Dosing
For pharmacological cardioversion of recent-onset atrial fibrillation:
- Oral single dose: 200-300 mg 3, 1
- Intravenous: 1.5-3.0 mg/kg administered over 10-20 minutes 3, 1
- This approach is reasonable only after safety has been demonstrated in a monitored setting 1
Critical Titration Principles
Flecainide has a long half-life (12-27 hours), requiring 3-5 days to reach steady-state plasma levels. 2 Therefore:
- Never increase dosage more frequently than every 4 days 2
- The optimal effect of a given dose may not be apparent for 2-3 days 2
- Avoid loading doses, as rapid titration increases proarrhythmic events and heart failure risk 2
Dose Adjustments for Special Populations
Severe Renal Impairment (CrCl ≤35 mL/min/1.73 m²)
- Initial dose: 100 mg once daily (or 50 mg twice daily) 2
- Frequent plasma level monitoring is mandatory 2
- Dosage increases should be made very cautiously after plasma levels plateau (>4 days) 2
Moderate Renal Disease
Concurrent Amiodarone Therapy
Therapeutic Monitoring
Target Plasma Levels
- Therapeutic range: 0.2-1.0 mcg/mL (trough levels) 2
- Increased adverse event risk: Levels >1.0 mcg/mL 2
- Monitor PR and QRS intervals during titration 1
When Plasma Monitoring is Required
- Severe renal failure 2
- Severe hepatic disease 2
- Concurrent amiodarone therapy 2
- Congestive heart failure 2
- Moderate renal disease 2
Absolute Contraindications
Never use flecainide in patients with:
- Structural heart disease (coronary artery disease, heart failure, significant LV dysfunction) - associated with increased mortality per CAST trial 1
- Sinus or AV node dysfunction 1
- Brugada syndrome 1
- Atrial flutter without concomitant AV nodal blocking therapy 1
Critical Safety Warnings
Proarrhythmic Risk
- Atrial flutter with 1:1 AV conduction is a potentially life-threatening complication requiring concomitant AV nodal blocking agents (beta-blockers or calcium channel blockers) 1
- Higher initial doses and rapid titration increase proarrhythmic events, especially in first few days 2
Drug Interactions
- Flecainide is metabolized by CYP2D6, which is genetically absent in 7-10% of the population 1
- CYP2D6 inhibitors (quinidine, fluoxetine, tricyclic antidepressants) can dramatically increase plasma concentrations 1
- Monitor closely with amiodarone, digoxin, ritonavir, saquinavir, and tipranavir 1
Cardiac Function Monitoring
- Use cautiously in patients with history of heart failure or myocardial dysfunction 2
- Watch for new or worsened heart failure, particularly in patients with chronic atrial fibrillation and structural heart disease 5
Efficacy by Arrhythmia Type
Based on clinical trial data: