What is the recommended dose of Amiodarone (antiarrhythmic medication) for an adult patient with a life-threatening arrhythmia requiring an intravenous (IV) bolus?

Amiodarone IV Bolus Dosing for Life-Threatening Arrhythmias

For life-threatening ventricular arrhythmias in hemodynamically stable adults, administer 150 mg IV over 10 minutes, followed by 1 mg/min for 6 hours, then 0.5 mg/min for the remaining 18 hours (maximum 2.2 g over 24 hours). 1, 2

Cardiac Arrest Protocol (VF/Pulseless VT)

If the patient is in cardiac arrest with ventricular fibrillation or pulseless ventricular tachycardia unresponsive to defibrillation and epinephrine, give 300 mg IV/IO bolus over 10 minutes, with a second 150 mg bolus if the rhythm persists. 1

Standard Loading Protocol for Hemodynamically Stable Patients

• Initial bolus: 150 mg IV diluted in 100 mL D5W over 10 minutes 1, 2
• First maintenance infusion: 1 mg/min for 6 hours (360 mg total) 1, 2
• Second maintenance infusion: 0.5 mg/min for remaining 18 hours (540 mg total) 1, 2
• Total first 24-hour dose: Approximately 1,050 mg 1, 2

Breakthrough Arrhythmias

• For breakthrough episodes of VF or hemodynamically unstable VT during the infusion, administer supplemental 150 mg boluses (mixed in 100 mL D5W) over 10 minutes 1, 2
• Do not exceed an initial infusion rate of 30 mg/min 2
• Mean daily doses above 2,100 mg are associated with increased risk of hypotension 2

Critical Administration Requirements

Use a central venous catheter for concentrations >2 mg/mL, as peripheral vein phlebitis occurs frequently at higher concentrations. 1, 2

• For infusions >1 hour, do not exceed 2 mg/mL concentration unless using a central line 1, 2
• Always use a volumetric infusion pump (not drop counters, which can underdose by up to 30%) 2
• Use an in-line filter during administration 2
• Administer in glass or polyolefin bottles containing D5W for infusions exceeding 2 hours 2

Absolute Contraindications

Do not administer amiodarone without a functioning pacemaker in patients with second- or third-degree AV block, sick sinus syndrome, or severe sinus node dysfunction. 1, 3

Monitoring Requirements During Infusion

• Continuous ECG monitoring for heart rate, AV conduction abnormalities, and QT prolongation is mandatory 3
• Blood pressure monitoring during infusion to detect hypotension (occurs in 16% of IV patients) 1, 2
• Monitor for bradycardia (occurs in 4.9% of IV patients) and heart block 1, 3
• If bradycardia or heart block develops, discontinue or reduce infusion rate immediately 3

Dose-Related Adverse Effects

• Hypotension is the most common adverse event (26% in clinical trials), with no clear dose-response relationship 4
• Bradycardia requiring intervention occurs in approximately 5% of patients 1
• Phlebitis at infusion site is concentration-dependent (use central line for concentrations >2 mg/mL) 1, 2

Special Considerations for Pre-Existing Bradycardia

If the patient has baseline bradycardia (e.g., heart rate 57 bpm), amiodarone is relatively contraindicated unless the clinical situation is immediately life-threatening and no safer alternatives exist. 3

• Drug-related bradycardia occurs in 4.9% regardless of dose 3
• If proceeding with life-threatening arrhythmia, monitor continuously and reduce infusion rate if heart rate decreases by ≥10 bpm 3
• Consider alternative agents (beta-blockers, calcium channel blockers) if the arrhythmia is not immediately life-threatening 3

Critical Drug Interactions During IV Infusion

• Digoxin: Reduce dose by 50% when starting amiodarone, as levels will double 1
• Warfarin: Reduce dose by 33-50% and monitor INR at least weekly (interaction peaks at 7 weeks) 1, 3
• QT-prolonging drugs: Avoid concomitant use without expert consultation 1
• Concomitant AV nodal blocking agents (beta-blockers, calcium channel blockers) create additive bradycardia risk 3

Efficacy Data

• Dose-response efficacy is demonstrated in refractory ventricular arrhythmias, with higher doses (500-1,000 mg/24h) showing significantly longer time to first arrhythmic event compared to lower doses (125 mg/24h) 1, 4
• The event rate decreases with increasing doses: 0.07,0.04, and 0.02 events per hour for 125,500, and 1,000 mg dose groups respectively 4
• Antiarrhythmic effect onset occurs rapidly, typically in less than 30 minutes 5

Maintenance Infusion Beyond 24 Hours

• Continue maintenance infusion at 0.5 mg/min (720 mg per 24 hours) using concentration of 1-6 mg/mL 2
• Maintenance infusion up to 0.5 mg/min can be continued for 2-3 weeks regardless of age, renal function, or left ventricular function 2
• Limited experience exists for IV amiodarone beyond 3 weeks 2