What is the recommended IV (intravenous) amiodarone loading dose and 24-hour infusion regimen for treating arrhythmias?

IV Amiodarone Loading Dose and 24-Hour Infusion Regimen

For chemical or electrical cardioversion of arrhythmias, administer 150 mg IV over 10 minutes as the loading dose, followed by 1 mg/min infusion for 6 hours (360 mg), then 0.5 mg/min for the remaining 18 hours (540 mg), with a maximum total dose of 2.2 g over 24 hours. 1, 2, 3

Standard Dosing Protocol

The recommended first 24-hour regimen consists of three distinct phases:

• Loading dose: 150 mg IV over 10 minutes 1, 2, 3
• Early maintenance: 1 mg/min for 6 hours (total 360 mg) 1, 2, 3
• Late maintenance: 0.5 mg/min for 18 hours (total 540 mg) 1, 2, 3
• Total 24-hour dose: Approximately 1050 mg, not to exceed 2.2 g 1, 2, 3

Supplemental Dosing for Breakthrough Arrhythmias

If breakthrough ventricular fibrillation or hemodynamically unstable ventricular tachycardia occurs during the infusion:

• Administer an additional 150 mg IV bolus over 10 minutes 3
• Mix in 100 mL D5W to minimize hypotension risk 3
• This supplemental dose can be repeated as needed while staying within the 2.2 g/24-hour maximum 3

Administration Requirements

Critical administration details to prevent complications:

• Use a volumetric infusion pump (never drop counters, which can underdose by up to 30%) 3
• Administer through a central venous catheter whenever possible 2, 3
• Use an in-line filter during administration 3
• For concentrations >2 mg/mL, a central line is mandatory to prevent phlebitis 3
• Maximum initial infusion rate: 30 mg/min 3
• Prepare in glass or polyolefin bottles with D5W (not evacuated glass containers) 3

Continuation Beyond 24 Hours

After the initial 24 hours, the maintenance infusion can be continued:

• Continue at 0.5 mg/min (720 mg per 24 hours) 3
• May increase rate to achieve effective arrhythmia suppression 3
• Can be safely continued for 2-3 weeks regardless of age, renal function, or left ventricular function 3
• Mean daily doses above 2100 mg are associated with increased hypotension risk 3

Monitoring Requirements During Infusion

Essential monitoring parameters include:

• Continuous cardiac monitoring for bradycardia and AV block 2
• Regular blood pressure monitoring for hypotension (occurs in 16% of patients) 1, 2
• ECG monitoring for QT prolongation 2
• Hypotension is the most common serious adverse effect during IV administration 1, 4

Clinical Context and Efficacy

The timing and dose are critical for efficacy:

• Cardioversion to sinus rhythm typically occurs after 6-8 hours 2
• Often requires ≥1000 mg total dose for successful conversion 2
• Conversion rates: 34-69% with bolus-only regimens, 55-95% with bolus plus continuous infusion 2, 5
• Higher doses (>1500 mg/day) are superior to placebo for recent-onset atrial fibrillation 5

Common Pitfalls to Avoid

• Do not use drop counter infusion sets - they can underdose by 30% due to altered surface properties 3
• Do not exceed 3 mg/mL concentration without a central line - peripheral vein phlebitis occurs frequently at higher concentrations 3
• Do not infuse faster than 30 mg/min initially - rapid infusions have caused hepatocellular necrosis and acute renal failure 3
• Do not use PVC containers for mixing - incompatibility may cause precipitation 3

Special Populations

Amiodarone is particularly valuable in specific clinical scenarios:

• Patients with structural heart disease where class IC drugs are contraindicated 2, 5
• Patients with left ventricular dysfunction 2, 5
• Hemodynamically stable monomorphic ventricular tachycardia 1
• Pre-excited atrial arrhythmias with rapid ventricular rates 1