What is flecainide and how is it used?

Flecainide: Clinical Uses, Efficacy, and Safety Considerations

Flecainide is a Class Ic antiarrhythmic medication primarily indicated for the prevention of paroxysmal supraventricular tachycardias (PSVT) and paroxysmal atrial fibrillation/flutter (PAF) in patients without structural heart disease. 1

Indications and Mechanism

• FDA-approved indications:

  • Prevention of paroxysmal supraventricular tachycardias (PSVT), including:
    • Atrioventricular nodal reentrant tachycardia
    • Atrioventricular reentrant tachycardia
    • Other supraventricular tachycardias with disabling symptoms
  • Prevention of paroxysmal atrial fibrillation/flutter with disabling symptoms
  • Prevention of documented life-threatening ventricular tachycardia 1

• Mechanism of action: Class Ic antiarrhythmic that markedly prolongs cardiac conduction with minimal effect on repolarization 2

Efficacy

• Highly effective for PSVT, with 80-90% efficacy rate (increasing to >90% when combined with a beta-blocker) 3
• Approximately 70-75% effective for paroxysmal atrial fibrillation 3
• More effective than quinidine and possibly more effective than disopyramide, mexiletine, tocainide, and propafenone in suppressing ventricular ectopic activity 4

Dosing and Administration

• Initial dose: 50 mg every 12 hours 3
• Maximum maintenance dose: 150 mg every 12 hours 3
• Renal impairment (CrCl ≤35 mL/min): Reduce to 100 mg once daily or 50 mg twice daily with frequent plasma level monitoring 3
• Target plasma levels: 0.2-1.0 mcg/mL (levels >0.7-1.0 mcg/mL require close monitoring) 3

Critical Contraindications

Flecainide should NOT be used in patients with:

• Structural heart disease or coronary artery disease 5, 3
• Significant ventricular dysfunction 5, 3
• Recent myocardial infarction 1
• Cardiogenic shock 3
• Sinus or AV conduction disease (without pacemaker) 3
• Brugada syndrome 3
• Atrial flutter (unless concomitant AV nodal therapy is used) 3

Adverse Effects

Cardiac Effects

• Proarrhythmic effects in 7-8% of patients (higher in those with serious ventricular tachycardia and reduced myocardial function) 4, 6
• QRS prolongation 3
• PR interval prolongation 3
• Negative inotropic effects 3
• New or worsened heart failure 3

Non-cardiac Effects

• Dizziness (most common) 3, 6
• Visual disturbances and difficulty focusing 4, 6
• Headaches 3

High-Risk Populations

Increased risk of flecainide toxicity in patients with:

• Renal impairment (CrCl ≤35 mL/min) 3, 7
• Hepatic dysfunction 3
• Heart failure 3
• Concomitant amiodarone therapy (requires 50% dose reduction) 3
• Electrolyte disturbances 3
• Female gender 3
• Coronary artery disease 3
• Previous myocardial infarction 3

Monitoring Requirements

• Baseline: ECG before initiation 3
• Follow-up: ECG after 3-5 days of therapy, at each dose change, and at regular intervals thereafter 3
• Plasma level monitoring: Particularly important in high-risk patients 3

Special Populations

Pregnancy

• Can be effective for ongoing management in pregnant patients with highly symptomatic SVT 5
• Should be avoided in the first trimester when risk of congenital malformations is greatest 5

Pediatric Patients

• All use should be directly supervised by a pediatric cardiologist 3

Management of Flecainide Toxicity

• First-line treatment: Sodium bicarbonate therapy (1-2 mEq/kg IV bolus followed by continuous infusion) 3
• Additional measures:
  • Continuous cardiac monitoring
  • Maintaining adequate oxygenation
  • Correcting electrolyte abnormalities
  • Calcium gluconate (1-2 g IV) to stabilize myocardial cell membranes 3

Drug Interactions

• Amiodarone: Reduce flecainide dose by 50% 3
• Digoxin: Monitor digoxin concentrations 3

Flecainide remains a valuable antiarrhythmic agent when used in appropriately selected patients without structural heart disease, with careful monitoring and dose adjustments based on individual patient factors.