What is the maximum dose of flecainide (anti-arrhythmic medication) for adults?

Maximum Dose of Flecainide

The maximum dose of flecainide for adults is 300 mg per day (150 mg every 12 hours) for supraventricular arrhythmias including atrial fibrillation and paroxysmal supraventricular tachycardia, and 400 mg per day (200 mg every 12 hours) for sustained ventricular tachycardia. 1, 2

Dosing by Indication

Supraventricular Arrhythmias (Atrial Fibrillation, PSVT)

• Starting dose: 50 mg every 12 hours 1, 2
• Titration: Increase by 50 mg twice daily every 4 days until efficacy is achieved 1, 2
• Maximum maintenance dose: 150 mg every 12 hours (300 mg/day total) 1, 2

The ACC/AHA/HRS guidelines explicitly state that PR and QRS intervals should be monitored during titration, and plasma trough levels should be kept below 0.7-1.0 mcg/mL 1, 3. This maximum of 300 mg/day applies to paroxysmal atrial fibrillation, atrial flutter (with concomitant AV nodal blockade), and other paroxysmal supraventricular arrhythmias 1, 2.

Sustained Ventricular Tachycardia

• Starting dose: 100 mg every 12 hours 2
• Titration: Increase by 50 mg twice daily every 4 days 2
• Maximum maintenance dose: 200 mg every 12 hours (400 mg/day total) 2

The FDA label emphasizes that most patients with sustained VT do not require more than 150 mg every 12 hours (300 mg/day), but the absolute maximum is 400 mg/day 2. Critically, higher initial doses and rapid titration in VT patients increase proarrhythmic events and congestive heart failure, particularly in the first few days 2.

Acute Cardioversion Dosing

For single-dose pharmacological cardioversion of recent-onset atrial fibrillation:

• Oral: 200-300 mg as a single dose 1, 3
• Intravenous: 2 mg/kg over 10 minutes 1

The "pill-in-the-pocket" approach using these single doses is reasonable once safety has been demonstrated in a monitored setting 3.

Critical Dosing Considerations

Renal Impairment

• Severe renal impairment (CrCl ≤35 mL/min): Initial dose should be 100 mg once daily (or 50 mg twice daily) with frequent plasma level monitoring required 2

Drug Interactions Requiring Dose Reduction

• With amiodarone: Reduce flecainide dose by 30-50% 1
• With dronedarone: Reduce flecainide dose by 50% 1

Monitoring Requirements

Flecainide has a long half-life of 12-27 hours, and steady-state plasma levels may not be achieved until 3-5 days of therapy at a given dose 2. Therefore, dose increases should occur no more frequently than every 4 days 2.

Absolute Contraindications to Any Dose

Never use flecainide in patients with:

• Structural heart disease, including coronary artery disease, heart failure, or significant left ventricular dysfunction 1, 3
• Sinus or AV conduction disease without a pacemaker 1
• Brugada syndrome 1
• Atrial flutter without concomitant AV nodal blocking therapy (risk of 1:1 AV conduction) 1

The contraindication in structural heart disease stems from the CAST trial, which demonstrated increased mortality with Class IC antiarrhythmics in post-MI patients 3.

Common Pitfalls

Watch for atrial flutter with 1:1 AV conduction - this potentially life-threatening complication requires concomitant AV nodal blocking agents (beta-blockers, calcium channel blockers, or digoxin) 1, 3. Flecainide can slow atrial flutter rate enough to allow 1:1 conduction through the AV node, paradoxically increasing ventricular rate 1.

CYP2D6 metabolism variability - Flecainide is metabolized by CYP2D6, which is genetically absent in 7-10% of the population and can be inhibited by quinidine, fluoxetine, and tricyclic antidepressants, dramatically increasing plasma concentrations 3.