What is the initial bolus dose of amiodarone for atrial fibrillation?

Amiodarone Initial Bolus Dose for Atrial Fibrillation

The initial bolus dose of amiodarone for atrial fibrillation is 150 mg administered intravenously over 10 minutes, followed by 1 mg/min for 6 hours, then 0.5 mg/min thereafter. 1

Dosing Protocol for Atrial Fibrillation

The FDA-approved dosing regimen for intravenous amiodarone consists of:

1. Initial Load: 150 mg in 100 mL (in D5W) infused over 10 minutes
2. Followed by: 1 mg/min for 6 hours
3. Followed by: 0.5 mg/min thereafter

This provides approximately 1000 mg over the first 24 hours of therapy 1.

Alternative Dosing Approaches

While the FDA-approved regimen is the standard approach, clinical guidelines suggest some variations:

• An alternative approach is initial administration of 5-7 mg/kg over 30-60 minutes, followed by 1.2-1.8 g/day continuous IV or divided oral doses until reaching a total of 10 g 2
• Some studies have used bolus doses ranging from 3 to 7 mg/kg body weight followed by infusions ranging from 900 to 3000 mg/day 3
• Higher dose regimens (>1500 mg/day) have shown superior efficacy compared to placebo in converting recent-onset atrial fibrillation to sinus rhythm 3

Efficacy Considerations

• Most conversions to normal sinus rhythm occur after 6-8 hours of therapy initiation 3
• Predictors of successful conversion include:
  • Shorter duration of atrial fibrillation
  • Smaller left atrial size
  • Higher amiodarone dose 3
• In patients with rapid ventricular rates (>135 bpm), a single bolus of 450 mg has been shown to be more effective than digoxin for heart rate control and conversion to sinus rhythm 4

Monitoring and Safety Considerations

When administering the initial bolus dose, monitor for:

• Hypotension: If it occurs, slow the infusion; add vasopressor drugs, positive inotropic agents, or volume expansion as needed 1
• Bradycardia and AV block: Slow the infusion or discontinue if these occur 1
• QT interval prolongation: Regular ECG monitoring is recommended 2

Contraindications

Intravenous amiodarone is contraindicated in patients with:

• Known hypersensitivity to any components of amiodarone, including iodine
• Cardiogenic shock
• Marked sinus bradycardia
• Second- or third-degree AV block unless a functioning pacemaker is available 1

Clinical Pearls

• Maintain potassium and magnesium levels above 4.0 mEq/L before and during therapy to prevent electrolyte imbalances 2
• Unlike beta-blockers, digitalis, and calcium channel blockers, amiodarone can be safely administered in patients with Wolff-Parkinson-White syndrome 2
• Amiodarone has a long half-life (average 58 days), which affects both its efficacy and side effect profile 2
• When transitioning from IV to oral therapy, adjust the oral loading dose based on the duration of previous IV therapy 2