Amiodarone Dosing for Atrial Fibrillation
For atrial fibrillation, start with an oral loading dose of 600-800 mg daily in divided doses until a total of 10 grams has been administered (typically 1-2 weeks), then reduce to a maintenance dose of 200 mg daily. 1
Oral Dosing Regimen
Loading Phase
- Administer 600-800 mg daily in divided doses (typically 2-3 times per day) until reaching a cumulative total of 10 grams 1, 2
- This loading phase typically requires 1-2 weeks depending on the daily dose used 2
- Alternative higher loading doses of 800-1600 mg/day may be used but are associated with more side effects 1
Maintenance Phase
- Reduce to 200 mg once daily after completing the 10-gram loading dose 1, 2
- Some patients may require 200-400 mg daily for optimal rhythm control 1
- Lower maintenance doses (200 mg daily or less) are associated with fewer side effects while maintaining efficacy 1
Intravenous Dosing (When Immediate Treatment Required)
Initial Loading
- 150 mg IV over 10 minutes, followed by 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours 1, 3
- Target approximately 1000 mg over the first 24 hours 3
Maintenance Infusion
- Continue at 0.5 mg/min (720 mg/24 hours) after the first 24 hours 3
- Can be continued for 2-3 weeks regardless of age, renal function, or left ventricular function 3
Breakthrough Episodes
- Administer 150 mg supplemental infusion over 10 minutes for breakthrough arrhythmias 3
Transitioning from IV to Oral
Begin oral amiodarone at 600-800 mg daily while continuing the IV infusion at 0.5 mg/min, particularly for patients who have received IV therapy for 1-3 weeks 2
- Continue oral loading until the 10-gram total is reached, then transition to 200-400 mg daily maintenance 2
- Monitor closely for bradycardia (occurs in 4.9% on IV, 1-3% on oral), hypotension (16% with IV), and AV block during the transition 2
Critical Monitoring Requirements
Cardiovascular Monitoring
- Check ECG for QT prolongation, bradycardia, and heart block before and during therapy 1, 2
- Monitor heart rate every 4-6 hours initially, then at least daily 2
- Continuous telemetry for at least 24 hours after IV discontinuation 2
Drug Interactions Requiring Dose Adjustments
- Reduce warfarin dose by 30-50% and check INR within 3-5 days, as amiodarone significantly increases INR 2
- Reduce digoxin dose by 50% immediately, as amiodarone doubles digoxin levels 2
- Reduce doses of beta-blockers and calcium channel blockers as amiodarone's rate-control effect develops 2
Efficacy Data
Amiodarone is more effective than class I agents or sotalol for maintaining sinus rhythm in atrial fibrillation. 1, 2
- In the CTAF study, 69% of patients on amiodarone maintained sinus rhythm versus 39% on propafenone or sotalol over 16 months 1
- In the AFFIRM study, 62% on amiodarone remained in sinus rhythm at 1 year compared to 23% on class I agents 1, 2
- Median time to AF recurrence was 487 days with amiodarone versus 74 days with sotalol 2
Common Pitfalls and Safety Considerations
Adverse Effects to Monitor
- Photosensitivity, pulmonary toxicity, polyneuropathy, GI upset, bradycardia, hepatic toxicity, thyroid dysfunction, and eye complications are potential long-term concerns 1
- Torsades de pointes is rare with amiodarone compared to other antiarrhythmics 1
- Approximately 18% of patients discontinue amiodarone due to side effects during long-term therapy 1
Administration Precautions for IV Formulation
- Use concentrations ≤2 mg/mL for peripheral IV to minimize phlebitis risk; higher concentrations require central venous access 3
- Must use volumetric infusion pump, not drop counters, as drop size reduction can cause up to 30% underdosing 3
- Administer in glass or polyolefin bottles only; avoid evacuated glass containers 3