What is the use and dosage of Tambocor (flecainide) in treating irregular heartbeat?

Tambocor (Flecainide) for Irregular Heartbeat

Flecainide is a Class IC antiarrhythmic drug primarily used for cardioversion and maintenance of sinus rhythm in atrial fibrillation (AF) and paroxysmal supraventricular tachycardia (PSVT), but should only be used in patients without structural heart disease, coronary artery disease, or heart failure due to significant proarrhythmic risk. 1

Primary Indications

Atrial Fibrillation

• First-line agent for patients with no or minimal structural heart disease 1
• Effective for both acute cardioversion and chronic rhythm maintenance 1
• For recent-onset AF, flecainide achieves cardioversion in 57-68% at 2-4 hours and 75-91% at 8 hours 1
• Oral administration typically produces response within 3 hours; IV within 1 hour 1

Paroxysmal Supraventricular Tachycardia (PSVT)

• Particularly effective for supraventricular tachycardia involving accessory bypass tracts (84-92% success rate) 2
• Recommended starting therapy for patients with disabling symptoms 1

Dosing Regimens

For PSVT and Paroxysmal AF 3

• Starting dose: 50 mg every 12 hours
• Titration: Increase by 50 mg twice daily every 4 days until efficacy achieved
• Maximum dose: 300 mg/day
• Substantial efficacy increase when escalating from 50 mg to 100 mg twice daily 3

For Sustained Ventricular Tachycardia 3

• Starting dose: 100 mg every 12 hours
• Titration: Increase by 50 mg twice daily every 4 days
• Usual effective dose: 150 mg every 12 hours (300 mg/day)
• Maximum dose: 400 mg/day
• Must initiate in-hospital with rhythm monitoring 3

Acute Cardioversion Dosing 1

• Oral: 200-300 mg single dose
• IV: 1.5-3.0 mg/kg over 10-20 minutes
• "Pill-in-the-pocket" approach: 200-300 mg oral dose for self-administration after safety established in hospital 1

Renal Impairment Adjustments 3

• Severe impairment (CrCl ≤35 mL/min): 100 mg once daily initially, with frequent plasma level monitoring
• Moderate impairment: 100 mg every 12 hours with plasma level monitoring
• Dosage increases should be made cautiously, allowing >4 days between adjustments

Critical Safety Considerations

Absolute Contraindications

• Structural heart disease (coronary artery disease, reduced left ventricular ejection fraction, heart failure) 1
• This restriction stems from increased mortality risk demonstrated in post-MI patients 1

Major Adverse Effects 1

• Hypotension during acute administration
• Atrial flutter with rapid 1:1 AV conduction - requires concomitant AV nodal blockade 1
• Proarrhythmia - particularly ventricular arrhythmias in susceptible patients 2, 4
• QRS prolongation - discontinue if QRS widens ≥25% from baseline 1
• Bradyarrhythmias in patients with pre-existing sinus node disease 4

Monitoring Requirements 1, 3

• ECG monitoring at initiation and with dose increases
• Watch for QRS duration increase >25% from baseline
• Steady-state plasma levels achieved after 3-5 days (half-life 12-27 hours) 3
• Therapeutic plasma levels: 200-500 ng/mL in children; similar monitoring useful in adults 3

Clinical Positioning

When to Use Flecainide

According to ACC/AHA/ESC guidelines, flecainide is positioned as: 1

• First choice for patients with no/minimal heart disease and paroxysmal AF
• Alternative option (after dofetilide/sotalol) for patients with hypertension without substantial left ventricular hypertrophy
• Possible option for coronary artery disease patients (though guidelines show conflicting placement - use extreme caution)

Comparative Efficacy

• Approximately doubles likelihood of maintaining sinus rhythm compared to placebo 1
• More effective than other AADs for acute termination of recent-onset AF 5
• Equivalent to other AADs (except amiodarone) for chronic suppression 5
• Inferior to amiodarone for long-term rhythm maintenance but better tolerated 1

Important Clinical Pitfalls

Rate Control Requirement

Always provide concomitant AV nodal blockade (beta-blocker, calcium channel blocker, or digoxin) because flecainide can convert AF to atrial flutter with paradoxically faster ventricular rates due to 1:1 AV conduction 1

Drug Interactions 3

• Amiodarone: Reduce flecainide dose by 50% and monitor closely
• Warfarin: May alter anticoagulation intensity when added or withdrawn 1

Underutilization Issue

Despite favorable safety profile in appropriate patients, flecainide remains underutilized due to misperceived proarrhythmic risk from the CAST trial, which studied post-MI patients - a population now contraindicated for flecainide use 5

Loading Dose Warning

Do not use loading doses - associated with increased proarrhythmic events and heart failure, particularly in first few days 3