Flecainide 200 mg Daily PRN for Atrial Fibrillation
Flecainide 200 mg as a single oral dose taken on an as-needed basis ("pill-in-the-pocket" approach) is appropriate and guideline-recommended for selected patients with paroxysmal atrial fibrillation, but only after safety has been demonstrated in a monitored hospital setting and only in patients without structural heart disease. 1
Patient Selection Criteria
Before considering PRN flecainide, you must confirm the patient meets ALL of the following criteria:
Absolute Requirements
- No structural heart disease (no coronary artery disease, heart failure, significant left ventricular dysfunction, or left ventricular hypertrophy) 1, 2
- No sinus or AV node dysfunction 1, 3
- No bundle-branch block 1
- No QT interval prolongation (baseline QTc must be <500 ms) 1, 3, 4
- No Brugada syndrome 1, 3
- Paroxysmal AF only (not chronic atrial fibrillation, which has NOT been adequately studied and is NOT recommended) 2
Critical Safety Step
The first dose MUST be administered in a monitored hospital setting to observe for:
- Conversion-related bradycardia from sinus or AV node dysfunction 1
- Atrial flutter with 1:1 AV conduction (a potentially life-threatening complication) 1, 3
- Hypotension 1
- Excessive QRS widening (>150% baseline) 1
Only after demonstrating safety in hospital can the patient self-administer at home. 1
Mandatory Concomitant Therapy
You must prescribe a beta blocker or nondihydropyridine calcium channel antagonist (diltiazem or verapamil) BEFORE initiating pill-in-the-pocket flecainide. 1, 3
- The AV nodal blocking agent should be given at least 30 minutes before the flecainide dose 1
- Alternatively, maintain continuous background AV nodal blockade 1
- This prevents the potentially fatal complication of atrial flutter with 1:1 AV conduction, which can cause extremely rapid ventricular rates 1, 3, 2
Dosing Protocol
Single oral dose: 200-300 mg taken at onset of symptomatic AF 1, 3
- The 200 mg dose you mentioned is within guideline-recommended range 1, 3
- This approach is "marginally less effective than hospital-based cardioversion" but provides practical control and reassurance 1
- Conversion typically occurs within hours if effective 1
Why This Matters: The CAST Trial Context
The Cardiac Arrhythmia Suppression Trial (CAST) demonstrated that flecainide increased mortality (5.1% vs 2.3% placebo) in patients with prior myocardial infarction and ventricular arrhythmias. 2, 5, 6 This finding does NOT apply to appropriately selected patients without structural heart disease using flecainide for supraventricular arrhythmias. 5, 6, 7
The CAST results led to widespread but inappropriate fear of flecainide across all patient populations, resulting in underutilization in patients who would safely benefit. 5, 7
Common Pitfalls to Avoid
- Never use in chronic atrial fibrillation - this population had 10.5% rate of VT/VF in case series, versus 0.4% in paroxysmal AF 2, 8
- Never use without AV nodal blockade - risk of 1:1 atrial flutter conduction 1, 3, 2
- Never use in structural heart disease - this is the CAST population where mortality increased 2, 5
- Watch for CYP2D6 interactions - quinidine, fluoxetine, and tricyclics can dramatically increase flecainide levels (7-10% of population lacks this enzyme genetically) 3
- Correct electrolytes first - hypokalemia and hypomagnesemia amplify proarrhythmic risk 4
Efficacy Data
In appropriately selected patients with paroxysmal supraventricular tachycardia, flecainide achieved symptomatic improvement in 87% of patients. 8 For paroxysmal AF specifically, 73% improved symptomatically. 8 Flecainide has proven more effective than other antiarrhythmic drugs for acute termination of recent-onset AF. 7
Monitoring After Initiation
Once pill-in-the-pocket use is established: