Second Dose of Amiodarone: 150 mg IV/IO
The second dose of amiodarone for refractory ventricular fibrillation is 150 mg IV/IO.
Dosing Algorithm for Refractory VF
After the patient has received the initial 300 mg amiodarone dose and continues to have refractory VF despite multiple defibrillations and epinephrine, the evidence-based approach is straightforward:
Administer amiodarone 150 mg IV/IO as a single supplemental dose 1. This is the standard recommendation from the 2010 AHA ACLS Guidelines, which explicitly states: "An initial dose of 300 mg IV/IO can be followed by 1 dose of 150 mg IV/IO" 1.
Administration Details
- Route: IV or intraosseous (IO) - both are acceptable
- Preparation: Mix 150 mg in 100 mL D5W
- Infusion time: Give over 10 minutes to minimize hypotension 2
- Timing: Administer when VF/pulseless VT persists or recurs after the initial 300 mg dose
Important Caveats
This is the only recommended second dose - guidelines specify "1 dose of 150 mg," not multiple repeat doses 1. The maximum recommended dose in the first 24 hours should not exceed approximately 2100 mg total, as higher doses are associated with increased risk of hypotension 3.
Monitor for hypotension and bradycardia, which are the most common adverse effects requiring intervention 1, 2. The formulation containing polysorbate 80 (older formulation) causes more hypotension than the captisol-based formulation, though both are effective 4.
Clinical Context
While amiodarone improves short-term survival to hospital admission compared to placebo or lidocaine 1, 5, no antiarrhythmic drug has been proven to increase survival to hospital discharge or favorable neurologic outcome 1, 4, 6. The primary goal is to facilitate successful defibrillation and prevent recurrent arrhythmias, not to pharmacologically convert VF 4.
Do not delay CPR or defibrillation to establish vascular access for amiodarone - these interventions have stronger evidence for improving survival 4.
Alternative if Amiodarone Unavailable
If amiodarone is not available, lidocaine may be considered as an alternative, though it has inferior evidence 1. Initial lidocaine dose is 1 to 1.5 mg/kg IV, with additional doses of 0.5 to 0.75 mg/kg at 5-10 minute intervals up to a maximum of 3 mg/kg 1.