What is the recommended dosing for flecainide (antiarrhythmic medication) in patients with atrial fibrillation?

Flecainide Dosing for Atrial Fibrillation

For atrial fibrillation, start flecainide at 50 mg every 12 hours and increase by 50 mg twice daily every 4 days as needed, up to a maximum of 150 mg every 12 hours (300 mg/day total). 1, 2, 3

Initial Dosing Strategy

• Begin with 50 mg twice daily (100 mg/day total) for patients with paroxysmal atrial fibrillation or paroxysmal supraventricular tachycardia 1, 3
• The FDA label specifies this starting dose for PSVT and PAF patients, with dose escalation every 4 days based on efficacy 3
• Do not use loading doses - flecainide has a long half-life (12-27 hours) and steady-state levels require 3-5 days at a given dose 3

Dose Titration

• Increase in 50 mg twice daily increments every 4 days until efficacy is achieved 1, 3
• The 2014 AHA/ACC/HRS guidelines specify a dosing range of 50-200 mg every 12 hours for maintenance therapy 1
• Maximum dose is 150 mg twice daily (300 mg/day total) for paroxysmal supraventricular arrhythmias including atrial fibrillation 1, 3
• A substantial increase in efficacy occurs when escalating from 50 mg to 100 mg twice daily without proportional increase in adverse effects 3

Acute Cardioversion Dosing

For pharmacological cardioversion of acute atrial fibrillation:

• Oral: 200-300 mg as a single dose 1
• Intravenous: 1.5-3.0 mg/kg over 10-20 minutes 1
• The "pill-in-the-pocket" approach (single oral dose for self-administration) is reasonable once safety has been demonstrated in a monitored setting 1

Monitoring Requirements

• Monitor PR and QRS intervals during dose titration - the ACC recommends checking these conduction parameters with each dose adjustment 2
• Measure trough plasma levels (obtained <1 hour pre-dose) and keep below 0.7-1.0 mcg/mL 2
• Obtain baseline ECG before initiation and repeat with dose changes 2, 3
• Initiate therapy in-hospital for patients with sustained ventricular tachycardia, though outpatient initiation is acceptable for supraventricular arrhythmias in selected patients 1, 3

Dose Adjustments for Special Populations

Renal impairment:

• For creatinine clearance ≤35 mL/min/1.73 m², start at 100 mg once daily (or 50 mg twice daily) 3
• Frequent plasma level monitoring is required to guide further adjustments 3

Pediatric dosing:

• Under 6 months: approximately 50 mg/M² body surface area daily, divided into 2-3 doses 3
• Over 6 months: may increase to 100 mg/M² per day 3
• Maximum: 200 mg/M² per day 3

Critical Contraindications

Absolute contraindications include:

• Structural heart disease (coronary artery disease, heart failure, significant left ventricular dysfunction) 1, 2
• Sinus or AV node dysfunction 1, 2
• Brugada syndrome 1, 2
• Atrial flutter without concomitant AV nodal blocking therapy 1, 2

Common Pitfalls

• Never use flecainide in patients with structural heart disease - this is associated with increased mortality as demonstrated in the CAST trial 1
• Avoid rapid dose escalation - increasing doses more frequently than every 4 days increases proarrhythmic risk, particularly in the first few days 3
• Watch for atrial flutter with 1:1 AV conduction - this potentially life-threatening complication requires concomitant AV nodal blocking agents 1, 2
• Flecainide is metabolized by CYP2D6, which is genetically absent in 7-10% of the population and can be inhibited by quinidine, fluoxetine, and tricyclics - these interactions can dramatically increase plasma concentrations 1

Efficacy Data

• In dose-response studies, 86% of patients with paroxysmal supraventricular tachycardia and 61% of patients with paroxysmal atrial fibrillation remained arrhythmia-free on 150 mg twice daily 4
• Long-term studies show 87% of patients remained free of symptomatic SVT over a mean follow-up of 3.9 years, with median dosage of 100 mg twice daily 5
• Complete response rates for paroxysmal atrial fibrillation range from 52-64% in clinical trials 6, 7, 8