What is the recommended dose and frequency of amiodarone for atrial fibrillation?

Amiodarone Dosing for Atrial Fibrillation

For atrial fibrillation, amiodarone should be administered with an oral loading dose of 800 mg daily for 1 week, followed by 600 mg daily for 1 week, then 400 mg daily for 4-6 weeks, with a maintenance dose of 200 mg daily. 1

Intravenous Administration for Acute Setting

When rapid heart rate control is needed in the acute setting:

• Initial dose: 150 mg IV over 10 minutes
• Maintenance infusion: 0.5 to 1 mg/min IV 2
• Onset of action: May take days for full effect
• Class recommendation: Class IIa, Level of Evidence C

Oral Administration Protocol

Loading Phase

• Week 1: 800 mg daily in divided doses
• Week 2: 600 mg daily in divided doses
• Weeks 3-6: 400 mg daily in divided doses
• Total loading: Continue until approximately 10 g total dose is reached 2, 1

Maintenance Phase

• Long-term dose: 200 mg daily 2, 1
• Duration: Indefinite for persistent AF requiring rhythm control

Special Considerations

Transitioning from IV to Oral Therapy

• If IV amiodarone used <1 week: Start 800-1600 mg oral daily
• If IV amiodarone used 1-3 weeks: Start 600-800 mg oral daily
• If IV amiodarone used >3 weeks: Start 400 mg oral daily 2, 1

Efficacy Monitoring

• Amiodarone has a long half-life (15-100 days, average 30 days) 3
• Maximum effects may not be seen for 90-150 days 3
• Antiarrhythmic protection may persist for up to 150 days after discontinuation 3

Side Effects and Monitoring

Major Side Effects

• Hypotension (especially with IV administration)
• Bradycardia and heart block (1-3% of patients)
• Pulmonary toxicity (0.3% annual rate)
• Thyroid dysfunction (both hypo- and hyperthyroidism)
• QT interval prolongation
• Corneal deposits and optic neuropathy
• Skin discoloration
• Warfarin interaction (requires dose reduction) 2, 1

Monitoring Protocol

• Baseline: Complete history, physical exam, chest radiograph, thyroid studies, liver function tests, pulmonary function tests
• Follow-up: Thyroid studies, liver function tests, and directed physical exam every 6 months
• As needed: Chest radiograph, pulmonary function tests if respiratory symptoms develop
• Warfarin adjustment: Reduce warfarin dose by one-third to one-half when co-administered 1

Clinical Efficacy

• Amiodarone is highly effective for maintaining sinus rhythm, with 62% of patients remaining in sinus rhythm at 1 year compared to 23% on class I agents 1
• Maintenance doses of 200-400 mg/day are typically effective for controlling atrial fibrillation 3, 4
• Success rates of 79% have been reported in patients with AF refractory to other agents 4

Important Caveats

• Chronic AF lasting >1 year is associated with lower success rates for maintaining sinus rhythm (57% vs. higher rates in more recent onset) 4
• Left atrial size, age, gender, and etiology of AF are not reliable predictors of amiodarone efficacy 4
• In minimally symptomatic AF patients already on anticoagulation, the risks of long-term amiodarone may outweigh benefits 1

Amiodarone's long half-life and delayed onset of action require patience when initiating therapy, but its high efficacy makes it valuable for AF patients who have failed other treatments.