Amiodarone Loading Protocol for Slow Oral Administration
The recommended oral amiodarone loading regimen is 800 mg daily for 1 week, followed by 600 mg daily for 1 week, 400 mg daily for 4-6 weeks, and then a maintenance dose of 200 mg daily. 1
Loading Dose Protocol
Initial Loading Phase
- Week 1: 800 mg daily in divided doses
- Week 2: 600 mg daily in divided doses
- Weeks 3-6/8: 400 mg daily in divided doses
Maintenance Phase
- Long-term: 200 mg daily 1
Clinical Considerations
Efficacy Timeline
- The slow loading approach results in therapeutic effects developing over 1-3 weeks 1
- Maximum antiarrhythmic effects may not be fully achieved until 90-150 days of treatment 2
- This gradual onset is due to amiodarone's long half-life (approximately 30 days, range 15-100 days) 2
Monitoring During Loading
- ECG monitoring for:
- QT interval prolongation
- Bradycardia
- Heart block
- Regular assessment of:
- Vital signs
- Symptoms of toxicity (pulmonary, thyroid, liver)
Alternative Loading Approaches
For patients requiring more rapid effect:
- Higher-dose oral loading: Some studies have used 50 mg/kg/day for 3 days, then 30 mg/kg/day for 2 days, followed by maintenance therapy 3
- Combined IV/oral loading: Can shorten time to optimal arrhythmia control (20±18 days vs 105±83 days with oral loading alone) 4
Special Considerations
Dose Adjustments
- Reduce warfarin dose by 50% when co-administered with amiodarone 1
- Reduce digoxin dose by 30-50% when co-administered with amiodarone 1
- Patients with renal or hepatic dysfunction may require dose adjustments
Monitoring Requirements
- ECG: Baseline and periodic monitoring
- Thyroid function tests: Every 6 months
- Liver function tests: Every 6 months
- Pulmonary function tests: Baseline and as clinically indicated
- Ophthalmologic examination: Baseline and periodically
Efficacy and Outcomes
- Amiodarone maintains sinus rhythm in approximately 65% of patients with atrial fibrillation at 16 months, compared to 37% with sotalol or propafenone 5
- For ventricular arrhythmias, success rates of 79-92% have been reported with maintenance doses of 100-400 mg/day 6, 7
Potential Adverse Effects
- Cardiovascular: Bradycardia, QT prolongation, heart block
- Pulmonary: Interstitial pneumonitis, fibrosis
- Endocrine: Hypo/hyperthyroidism
- Dermatologic: Photosensitivity, skin discoloration
- Neurologic: Peripheral neuropathy, tremor, ataxia
- Ophthalmologic: Corneal microdeposits, optic neuropathy
- Gastrointestinal: GI upset, constipation
The slow loading protocol balances the need to achieve therapeutic levels with minimizing adverse effects. While faster loading protocols exist, the standard approach provides a reasonable timeline for most non-emergent situations while minimizing risk of toxicity.