What is the appropriate amiodarone dosing for an adult with shock‑refractory ventricular tachycardia who is hypotensive?

Amiodarone Dosing for Shock-Refractory Ventricular Tachycardia with Hypotension

For shock-refractory ventricular tachycardia with hypotension, administer amiodarone 300 mg IV/IO as a rapid infusion over 10 minutes, followed by a continuous infusion of 1 mg/min for 6 hours, then 0.5 mg/min thereafter, with a second bolus of 150 mg IV/IO available for breakthrough episodes. 1, 2

Initial Bolus Dosing

• The first-line dose is 300 mg IV/IO infused over 10 minutes for VF or pulseless VT unresponsive to CPR, defibrillation, and vasopressor therapy. 1
• The FDA-approved labeling specifies 150 mg in 100 mL D5W infused over 10 minutes as the initial load, which represents the same 150 mg dose but in a standardized dilution. 2
• An alternative dosing of 5 mg/kg has been studied (approximately 300-400 mg for average adults) and showed improved hospital admission rates compared to placebo or lidocaine in out-of-hospital cardiac arrest. 1

Continuous Infusion Protocol

• After the initial bolus, immediately start 1 mg/min for 6 hours (360 mg total over this period). 1, 2
• Then reduce to 0.5 mg/min for the remaining 18 hours (540 mg over this period). 1, 2
• This delivers approximately 1,000 mg over the first 24 hours of therapy. 2

Breakthrough Arrhythmia Management

• For recurrent VT/VF during the infusion, give a supplemental bolus of 150 mg IV/IO over 10 minutes. 1, 2
• This supplemental dose can be repeated as needed for breakthrough episodes. 2
• Research demonstrates that higher cumulative doses (1,050-2,100 mg/24h) significantly reduced the need for supplemental boluses compared to lower doses (525 mg/24h). 3, 4

Critical Hemodynamic Considerations

Hypotension is the most common adverse effect (occurring in 26-37% of patients) and requires immediate management: 3, 4, 5

• Slow the infusion rate immediately if hypotension develops. 1, 2
• Add vasopressor drugs (epinephrine or norepinephrine) as needed. 1
• Consider positive inotropic agents if cardiogenic shock is present. 1
• Ensure adequate volume expansion. 1
• Administering a vasopressor before amiodarone can prevent hypotension, as demonstrated in animal studies. 1

The hypotensive effect is attributed to vasoactive solvents (polysorbate 80 and benzyl alcohol) in the IV formulation, not amiodarone itself. 1

Bradycardia and Conduction Block Management

• Slow the infusion or discontinue amiodarone if symptomatic bradycardia or AV block develops. 1, 2
• Symptomatic bradycardia occurred in 4-11% of patients in clinical trials. 5
• Amiodarone is contraindicated in patients with second- or third-degree AV block without a functioning pacemaker. 2

Evidence Quality and Efficacy Expectations

The evidence supporting amiodarone in this setting shows modest efficacy:

• Two randomized controlled trials demonstrated that amiodarone improved hospital admission rates (short-term survival) but did not improve survival to hospital discharge compared to placebo or lidocaine. 1
• In patients with recurrent, refractory VT, the response rate (surviving 24 hours without another hypotensive event) was 40.3% with amiodarone as a single agent. 3
• Amiodarone is poorly effective for acute termination of sustained monomorphic VT (only 29% termination rate within 20 minutes), likely due to the slow onset of its class III effects. 6
• The primary benefit is preventing recurrence and reducing the number of life-threatening arrhythmic events rather than immediate termination. 1

Dosing Algorithm Summary

Time Point	Dose	Route	Purpose
Initial	300 mg over 10 min	IV/IO	First-line for shock-refractory VT [1]
0-6 hours	1 mg/min continuous	IV/IO	Maintenance loading [2]
6-24 hours	0.5 mg/min continuous	IV/IO	Continued suppression [2]
Breakthrough	150 mg over 10 min	IV/IO	Repeat as needed [2]

Common Pitfalls to Avoid

• Do not delay electrical cardioversion if the patient becomes hemodynamically unstable during amiodarone infusion—amiodarone works slowly and electrical therapy remains the definitive treatment for unstable VT. 1
• Do not combine amiodarone with other QT-prolonging antiarrhythmics (procainamide, sotalol) without specialist consultation due to excessive QT prolongation risk. 1
• Do not use amiodarone in polymorphic VT with long QT (torsades de pointes)—this requires magnesium sulfate 1-2 g IV, not amiodarone. 1
• Monitor for cardiogenic shock, which is listed as a contraindication to amiodarone but may be difficult to distinguish from amiodarone-induced hypotension. 2

Alternative Considerations

• Lidocaine (1-1.5 mg/kg IV) is the alternative if amiodarone is unavailable, though it has no proven survival benefit and is less effective than amiodarone for hospital admission rates. 1
• Procainamide is preferred for hemodynamically stable monomorphic VT in patients without severe heart failure or acute MI, but is not appropriate for shock-refractory VT with hypotension. 1