Amiodarone Loading Dose for Life-Threatening Arrhythmias
For life-threatening arrhythmias, the recommended loading dose of amiodarone is 150 mg IV administered over 10 minutes (which may be repeated if necessary), followed by 1 mg/min for 6 hours, then 0.5 mg/min thereafter, with a total dose not exceeding 2.2 g over 24 hours. 1
Intravenous Loading Protocol
The FDA-approved intravenous loading protocol for amiodarone in life-threatening ventricular arrhythmias consists of approximately 1000 mg over the first 24 hours, delivered in three phases 1:
- Initial load: 150 mg IV over 10 minutes (in 100 mL D5W)
- Followed by: 1 mg/min infusion for 6 hours (360 mg)
- Followed by: 0.5 mg/min infusion thereafter (720 mg per 24 hours)
For breakthrough episodes of ventricular fibrillation or hemodynamically unstable ventricular tachycardia, repeat the initial 150 mg loading dose 1
The onset of antiarrhythmic effect occurs rapidly, typically in less than 30 minutes 2
Administration Considerations
Amiodarone must be delivered by a volumetric infusion pump, preferably through a central venous catheter dedicated to that purpose 1
Use an in-line filter during administration to prevent particulate matter 1
For concentrations greater than 2 mg/mL, a central venous catheter is required to minimize phlebitis 1
Amiodarone infusions exceeding 2 hours must be administered in glass or polyolefin bottles containing D5W 1
Do not exceed an initial infusion rate of 30 mg/min to avoid severe hypotension 1
Oral Loading Dose
For patients requiring oral loading (for stable ventricular arrhythmias), the recommended dose is 800 to 1,600 mg per day in divided doses until a total of 10 g has been administered 2, 3
After the loading phase, reduce to a maintenance dose of 200 to 400 mg per day 2, 3
Monitoring and Adverse Effects
The most common adverse reactions during IV amiodarone administration include 1:
- Hypotension (most common, occurring in approximately 26% of patients) 4
- Bradycardia and AV block
- Hepatocellular necrosis and acute renal failure (with excessively rapid infusion)
If hypotension occurs, slow the infusion rate and consider adding vasopressor drugs, positive inotropic agents, or volume expansion 1
If bradycardia or AV block develops, slow the infusion or discontinue administration 1
Patients with severe left ventricular dysfunction are at higher risk of developing significant hypotension during the loading phase 5
Clinical Considerations
Dose-response studies have demonstrated that higher loading doses (1000 mg/24 hours) are more effective than lower doses (125 mg/24 hours) in suppressing life-threatening ventricular arrhythmias 4
The time to first arrhythmic event increases and the number of supplemental boluses needed decreases with higher loading doses 4
For patients transitioning from IV to oral therapy, the oral dosing should be based on duration of IV therapy, with higher oral doses (800-1,600 mg daily) recommended for patients who received IV therapy for less than one week 3
Amiodarone shows considerable interindividual variation in response, so close monitoring with dose adjustment is essential 1