What is the recommended dosing and infusion rate of amiodarone (anti-arrhythmic medication) for an adult patient in ventricular fibrillation (VF) who is unresponsive to initial defibrillation attempts and cardiopulmonary resuscitation (CPR)?

Amiodarone Dosing and Infusion Rate in Ventricular Fibrillation

Initial Bolus Dose for Cardiac Arrest

For adult patients in ventricular fibrillation unresponsive to CPR and defibrillation, administer 300 mg IV/IO as a rapid bolus, followed by a second dose of 150 mg IV/IO if VF persists. 1, 2

Dosing Algorithm for VF/Pulseless VT:

• First dose: 300 mg IV/IO administered as a rapid bolus (can be given over 10 minutes if mixed in 100 mL D5W to minimize hypotension) 1, 2
• Second dose: 150 mg IV/IO if VF/pulseless VT persists after the initial dose 1, 2
• Timing: Amiodarone should only be given after multiple defibrillation attempts, epinephrine administration, and continued high-quality CPR 1
• Maximum during arrest: Do not exceed 300 mg for the initial dose and only one 150 mg supplemental dose during the cardiac arrest 1

Post-Resuscitation Infusion Protocol

After successful resuscitation or for hemodynamically stable ventricular arrhythmias, transition to a continuous infusion following the standard loading protocol. 3, 2

Standard 24-Hour Infusion Regimen:

• Loading infusion: 150 mg over 10 minutes (for rapid loading) 3, 4, 2
• First 6 hours: 1 mg/min (360 mg total) 3, 4, 2
• Next 18 hours: 0.5 mg/min (540 mg total) 3, 4, 2
• Total first 24 hours: Approximately 1000 mg 3, 4, 2
• Maintenance beyond 24 hours: Continue at 0.5 mg/min (720 mg per 24 hours) for up to 2-3 weeks 2

Breakthrough Arrhythmias During Infusion:

• Supplemental boluses: 150 mg IV mixed in 100 mL D5W infused over 10 minutes to minimize hypotension 2
• Maximum infusion rate: Do not exceed 30 mg/min initial infusion rate 2

Critical Administration Requirements

Amiodarone must be delivered by volumetric infusion pump through a central venous catheter whenever possible, with continuous ECG monitoring. 4, 2

Administration Specifications:

• Concentration limits: Do not exceed 2 mg/mL for peripheral IV access; concentrations >2 mg/mL require central venous catheter due to high incidence of phlebitis 2
• Infusion equipment: Use volumetric infusion pump (not drop counters, which can underdose by up to 30%) 2
• In-line filter: Required during administration 2
• Diluent: Must use D5W; do not use evacuated glass containers for admixing 2
• Container type: For infusions >1 hour, use glass or polyolefin bottles only 2

Monitoring and Safety Considerations

Hypotension occurs in approximately 26% of patients and is the most common adverse effect, primarily from vasoactive solvents in the IV formulation. 1, 5

Mandatory Monitoring:

• Continuous ECG: Monitor for bradycardia (4.9% incidence), heart block, QT prolongation, and hypotension (16-26% incidence) 1, 4, 5
• Bradycardia management: If heart rate decreases significantly, reduce infusion rate immediately 4
• Blood pressure: Administer vasopressors before amiodarone when possible to prevent hypotension 1

Contraindications:

• Absolute: Second- or third-degree AV block or sick sinus syndrome without pacemaker 3
• Relative: Severe sinus node dysfunction, marked sinus bradycardia 3

Evidence Quality and Clinical Context

Amiodarone is a Class IIb recommendation (benefit-to-risk ratio less well established) for shock-refractory VF/pulseless VT, but evidence shows it improves short-term survival to hospital admission compared to placebo or lidocaine. 1

Key Evidence Points:

• The dosing recommendations are based on the ACLS guidelines from the American Heart Association, which represent the standard of care for cardiac arrest management 1
• Studies demonstrate that amiodarone substantially improves survival and hospital admission rates in patients with shock-resistant, out-of-hospital ventricular fibrillation 3
• The 300 mg/150 mg bolus protocol is specifically designed for the cardiac arrest setting and differs from the slower loading protocol used for stable ventricular arrhythmias 1, 2

Common Pitfalls to Avoid

• Do not delay defibrillation or epinephrine to administer amiodarone—it is only given after these interventions have been attempted 1
• Do not use drop counter infusion sets—they can underdose by up to 30% 2
• Do not infuse concentrations >2 mg/mL peripherally—this causes severe phlebitis 2
• Do not confuse with amrinone—fatal complications can occur if drugs are interchanged 3
• Do not exceed recommended bolus doses during arrest—higher doses increase hypotension risk without improving outcomes 1, 2