Appropriate Amiodarone Loading Dose
For oral loading, administer 600-800 mg daily in divided doses until a total of 10 grams has been given (typically 2-4 weeks), then transition to maintenance dosing of 200-400 mg daily. 1, 2
Oral Loading Regimens by Clinical Context
Standard Outpatient Loading
- Start with 600-800 mg daily in divided doses until cumulative dose of 10 grams is reached 1, 2
- This typically requires 2-4 weeks of loading 2
- After loading is complete, reduce to maintenance dose of 200 mg daily for atrial fibrillation or 200-400 mg daily for ventricular arrhythmias 1, 2
High-Dose Inpatient Loading (Unstable Patients)
- For critically ill patients with frequent refractory ventricular arrhythmias, use 800-1600 mg daily in divided doses until 10 grams total is administered 1, 2
- Higher initial doses (up to 1200 mg daily) may be considered with close inpatient monitoring, though this increases adverse effect risk 2
- This aggressive approach can achieve arrhythmia control within 1-6 days in most patients 3
Intravenous Loading Protocol
First 24 Hours
- Administer approximately 1000 mg over the first 24 hours using the following regimen 4:
- Loading infusion: 150 mg over 10 minutes
- Slow loading infusion: 1 mg/min for 6 hours (360 mg)
- Maintenance infusion: 0.5 mg/min for remaining 18 hours (540 mg)
- For breakthrough ventricular fibrillation or unstable ventricular tachycardia, give supplemental 150 mg boluses over 10 minutes 1, 4
Beyond 24 Hours
- Continue maintenance infusion at 0.5 mg/min (720 mg per 24 hours) 4
- This rate can be safely continued for 2-3 weeks regardless of age, renal function, or left ventricular function 4
- Mean daily doses above 2100 mg are associated with increased hypotension risk 4
Critical Administration Requirements
Route and Monitoring
- Administer IV amiodarone through a central venous catheter whenever possible to avoid peripheral vein phlebitis 4
- Use concentrations ≤2 mg/mL for peripheral administration; concentrations >2 mg/mL require central access 4
- Use volumetric infusion pump (never drop counters) as surface tension changes can cause up to 30% underdosing 4
- Administer through in-line filter 4
Contraindications and Precautions
- IV amiodarone is contraindicated in patients with bradycardia or second/third-degree heart block without a pacemaker 5, 4
- In patients with baseline heart rate <60 bpm, use extreme caution and consider alternative agents unless immediately life-threatening 5
- Continuous ECG monitoring is mandatory during IV administration 5
- If bradycardia develops (decrease of ≥10 bpm), reduce infusion rate immediately 5
Transitioning from IV to Oral Therapy
Duration-Based Conversion
The oral dose depends on duration of IV therapy 1, 2:
- IV <1 week: Transition to 800-1600 mg oral daily 1, 2
- IV 1-3 weeks: Transition to 600-800 mg oral daily 1, 2
- IV >3 weeks: Transition to 400 mg oral daily 1, 2
This accounts for tissue accumulation during IV therapy, as patients receiving longer IV courses have already achieved significant drug loading 2
Common Pitfalls and Monitoring
Drug Interactions
- Reduce digoxin dose by 50% when starting amiodarone, as digoxin levels predictably double 5
- Reduce warfarin dose by one-third to one-half and monitor INR weekly for first 6 weeks, as interaction effects peak at 7 weeks 5
- Avoid grapefruit juice, which increases amiodarone plasma levels 5
Toxicity Surveillance
- Monitor for bradycardia, QT prolongation, and hypotension during loading 1, 2
- Watch for pulmonary toxicity (cough, dyspnea) which can develop rapidly without warning 1
- Check liver and thyroid function every 6 months during maintenance 5
- Use the lowest effective dose to minimize toxicity, as adverse effects correlate with total drug exposure 1, 6
Key Safety Consideration
The extremely long half-life (58 days average, range 15-100 days) means full antiarrhythmic effect may take days to weeks despite adequate serum levels 2, 5. This also means toxicity can persist long after discontinuation.