What is the recommended dosing for Flecainide (antiarrhythmic medication) in patients with atrial fibrillation or supraventricular tachycardia?

Flecainide Dosing for Atrial Fibrillation and Supraventricular Tachycardia

For patients with atrial fibrillation or supraventricular tachycardia, the recommended flecainide dosing is 50-100 mg twice daily initially, with gradual increases up to 200-300 mg daily in divided doses, based on response and tolerability. 1

Initial Dosing and Titration

For Paroxysmal Supraventricular Tachycardia (PSVT):

• Starting dose: 50 mg every 12 hours 1
• Titration: Increase in increments of 50 mg twice daily every four days until efficacy is achieved 1
• Maximum recommended dose: 300 mg/day 1

For Paroxysmal Atrial Fibrillation (PAF):

• Starting dose: 50 mg every 12 hours 1
• Titration: Increase in increments of 50 mg twice daily every four days until efficacy is achieved 1
• Substantial efficacy improvement often seen when increasing from 50 mg to 100 mg twice daily 1
• Maximum recommended dose: 300 mg/day 1

Monitoring and Dose Adjustment

• Wait at least 3-5 days between dose adjustments to allow steady-state plasma levels to be achieved 1
• Monitor for QRS widening, which should not exceed 150% of pretreatment QRS duration 2
• For patients not adequately controlled with twice-daily dosing, consider dosing at 8-hour intervals 1
• Once adequate arrhythmia control is achieved, consider dose reduction to minimize side effects 1

Special Populations

Patients with Renal Impairment:

• Reduce dose and monitor plasma levels more frequently 1

Children:

• Under 6 months: Initial dose of approximately 50 mg/m² body surface area daily, divided into 2-3 doses 1
• Over 6 months: Initial dose may be increased to 100 mg/m² per day 1
• Maximum recommended dose: 200 mg/m² per day 1
• Therapeutic plasma level in children: 200-500 ng/mL (up to 800 ng/mL may be required in some cases) 1

Efficacy

• Flecainide is effective in postponing the first recurrence of AF and reducing overall time spent in AF 2
• In clinical trials, flecainide demonstrated 87% symptomatic improvement in PSVT patients and 73% in PAF patients 3
• Higher doses (150 mg twice daily) resulted in 86% of PSVT patients and 61% of PAF patients having no tachycardia recurrence 4

Safety Considerations and Contraindications

Contraindications:

• Structural heart disease
• Coronary artery disease
• Left ventricular dysfunction
• Recent myocardial infarction 5

Monitoring for Adverse Effects:

• Cardiac adverse effects: proarrhythmic events, worsening heart failure, sinus pauses 3
• Common non-cardiac side effects: abnormal vision, dizziness, headaches 3
• Higher risk of cardiac side effects in patients with chronic atrial fibrillation and structural heart disease 3

Practical Considerations

• Initiate therapy in an outpatient setting for patients without structural heart disease 2
• For patients with sustained ventricular tachycardia, initiate in-hospital with rhythm monitoring 1
• Consider switching to another antiarrhythmic drug if flecainide does not provide adequate symptom control 5
• Long-term safety profile is favorable in patients without structural heart disease, with studies showing 93% probability of 12-month safe and effective treatment for PSVT 6

Key Pitfalls to Avoid

1. Never use flecainide in patients with structural heart disease due to increased risk of proarrhythmia
2. Avoid rapid dose escalation - always wait at least 4 days between dose increases
3. Do not exceed maximum recommended daily dose of 300 mg for supraventricular arrhythmias
4. Monitor for QRS widening as a sign of potential toxicity
5. Be aware that flecainide can convert atrial fibrillation to atrial flutter with rapid ventricular conduction

Flecainide has proven to be both effective and safe for long-term management of supraventricular arrhythmias in patients without structural heart disease, with most patients maintained on a median dose of 100 mg twice daily 7.