Oral Amiodarone Loading Regimen
The recommended oral amiodarone loading regimen is 600-800 mg daily for 7 days (total 4.2-5.6g), followed by a maintenance dose of 200-400 mg daily. 1
Standard Loading Protocol
The loading dose of oral amiodarone follows a specific regimen to rapidly achieve therapeutic levels:
- Initial loading phase: 600-800 mg daily in divided doses for 7 days 1
- Total loading dose: 4.2-5.6 grams
- Weight-independent dosing (standard for most patients)
- May be given as twice daily dosing (e.g., 400 mg twice daily) to improve tolerability
Conversion from IV to Oral Therapy
When transitioning from intravenous to oral amiodarone, the loading dose should be adjusted based on the duration of previous IV therapy 1:
| Duration of IV Use | Recommended Oral Amiodarone Dose |
|---|---|
| <1 week | 800-1600 mg daily |
| 1-3 weeks | 600-800 mg daily |
| >3 weeks | 400 mg daily |
Maintenance Dosing
After completing the loading phase:
- Standard maintenance dose: 200-400 mg daily 1
- Lower doses (200 mg daily) are often effective with fewer side effects
- Due to the extremely long half-life (average 58 days), the full therapeutic effect may take weeks to develop
Important Considerations
Bioavailability: Amiodarone has variable bioavailability (22-95%) that is enhanced when taken with food 1
Drug interactions: Amiodarone inhibits multiple CYP450 enzymes and P-glycoprotein, requiring dose adjustments of concomitant medications 1:
- Warfarin: Reduced clearance, potentially increasing INR
- Digoxin: Levels may double due to inhibition of renal tubular secretion
- Statins: Limit simvastatin to 20 mg daily when used with amiodarone
Monitoring during loading phase:
- QT interval prolongation
- Bradycardia
- Gastrointestinal side effects
- Neurological effects
Common Pitfalls and Caveats
- Side effects are dose-dependent: Higher loading doses (>1,800 mg/day) have been studied 2 but are associated with increased risk of side effects
- Early side effects: Nearly all patients on high maintenance doses (600 mg daily) develop side effects 3, which is why current guidelines recommend lower maintenance doses
- Electrolyte management: Potassium and magnesium levels should be maintained above 4.0 mEq/L before and during therapy 1
- Administration timing: Taking amiodarone with food improves absorption and may reduce gastrointestinal side effects
- Long half-life: Due to amiodarone's extremely long half-life, effects persist long after discontinuation, and drug should be tapered rather than stopped abruptly 1
The loading regimen described above represents the current standard of care based on guidelines from the American Heart Association, with consideration of the medication's unique pharmacokinetic properties and side effect profile.