Which antiarrhythmic is used as an initial 300 mg IV push in ACLS for shockable VF/pVT, with a potential second dose of 150 mg if needed?

• A. Amiodarone
• B. Lidocaine
• C. Magnesium sulfate
• D. Adenosine

Answer: (A)

When a shockable rhythm like ventricular fibrillation or pulseless ventricular tachycardia remains after defibrillation attempts, an antiarrhythmic is given to increase the chance of converting to a stable rhythm and prevent immediate recurrence. Amiodarone is the drug of choice in this setting because it acts broadly to suppress ventricular arrhythmias by prolonging the action potential and refractory period, improving the likelihood of maintaining ROSC during CPR. The standard dosing is a 300 mg IV push, with a potential additional 150 mg IV push if the arrhythmia persists after the initial dose.

Lidocaine can be considered if amiodarone isn’t available, but amiodarone is preferred due to better outcomes in this scenario. Magnesium sulfate is for torsades de pointes or severe magnesium deficiency, not the typical shockable VT/VF encountered in this context. Adenosine is used for certain SVTs, not for VT/VF.