Oral Amiodarone Loading Regimen
For ventricular arrhythmias, load with 800-1,600 mg per day in divided doses until a total of 10 grams has been given, then reduce to 200-400 mg daily; for atrial fibrillation, use 600-800 mg per day in divided doses until 10 grams total, then 200 mg daily. 1
Regimen Based on Indication
Ventricular Arrhythmias (Inpatient)
- Loading dose: 800-1,600 mg/day in divided doses
- Total loading: Continue until 10 grams cumulative dose achieved
- Maintenance: 200-400 mg/day 1
This typically takes 6-10 days at 1,200-1,600 mg/day or 10-13 days at 800 mg/day to reach the 10-gram threshold.
Atrial Fibrillation (Inpatient or Outpatient)
- Loading dose: 600-800 mg/day in divided doses
- Total loading: Continue until 10 grams cumulative dose achieved
- Maintenance: 200 mg/day 1
- Note: Higher initial dosages or IV dosing may be used in unstable inpatients
This approach takes approximately 12-17 days to achieve the 10-gram loading target.
Alternative High-Dose Single Loading Regimen
For recent-onset atrial fibrillation specifically, a single oral loading dose of 25-30 mg/kg body weight is highly effective (>85% conversion rate within 24 hours), with most conversions occurring after 6-8 hours. 2 This translates to approximately 1,800-2,100 mg for a 70-kg patient given as a single dose, followed by standard maintenance dosing of 10-15 mg/kg/day if conversion doesn't occur.
This single-dose approach is simpler, well-tolerated, and achieves faster conversion than divided dosing regimens for atrial fibrillation 2, though it's less commonly used in U.S. practice.
Transitioning from IV to Oral
When switching from IV amiodarone to oral therapy, the dose depends on duration of IV therapy 3:
- IV <1 week: Start 800-1,600 mg/day oral
- IV 1-3 weeks: Start 600-800 mg/day oral
- IV >3 weeks: Start 400 mg/day oral
Key Clinical Considerations
Divide daily doses to minimize gastrointestinal side effects (nausea, constipation). Most protocols use twice-daily or three-times-daily dosing during the loading phase.
Predictors of successful conversion include shorter arrhythmia duration, smaller left atrial size, and higher amiodarone doses 4. Patients meeting these criteria may respond to lower loading doses.
Adverse effects are dose-dependent and cumulative 1. The frequency of toxicity (pulmonary, thyroid, hepatic) correlates with total amiodarone exposure, making it critical to use the lowest effective dose and achieve therapeutic effect as quickly as possible before transitioning to maintenance.
Common Pitfalls
Underdosing during loading: The 10-gram cumulative target exists because amiodarone has a very long half-life (40-55 days) and extensive tissue distribution. Inadequate loading leads to delayed therapeutic effect.
Forgetting to reduce to maintenance: Continuing high loading doses beyond the 10-gram threshold significantly increases toxicity risk without additional benefit.
Not monitoring for bradycardia and QT prolongation: These are the most common acute adverse effects during oral loading 1.