What is the intravenous dosing regimen for Cordarone (amiodarone) in adult patients requiring rapid rhythm control of ventricular tachycardia, ventricular fibrillation, or refractory atrial fibrillation?

Cordarone (Amiodarone) Intravenous Dosing

For life-threatening ventricular arrhythmias or hemodynamically stable wide-complex tachycardia, administer a 150 mg IV bolus over 10 minutes, followed by 1 mg/min infusion for 6 hours, then 0.5 mg/min for 18 hours, delivering approximately 1 gram in the first 24 hours. 1

Standard IV Dosing Protocol

Rapid Loading Phase

• Initial bolus: 150 mg diluted in 100 mL of 5% dextrose (D5W) administered over 10 minutes 1
• This bolus may be repeated after 10-30 minutes if breakthrough arrhythmias occur 2
• For cardiac arrest or immediately life-threatening situations, the 150 mg bolus can be given over 10-15 minutes and repeated after 1 hour if needed 1

Maintenance Infusion

• Early maintenance: 1 mg/min for 6 hours (delivers approximately 360 mg) 2, 1
• Late maintenance: 0.5 mg/min for the remaining 18 hours (delivers approximately 540 mg) 2, 1
• Total 24-hour dose: Approximately 1000 mg from combined bolus and infusions 1
• Maximum cumulative dose: Do not exceed 2.2 grams within any 24-hour period 1

Administration Requirements

• Must use 5% dextrose in water (D5W) as the diluent; normal saline or lactated Ringer's causes precipitation 1
• Concentration should not exceed 2 mg/mL unless administered through a central venous catheter 1
• Use a central line whenever possible, as peripheral vein phlebitis occurs frequently with concentrations >2 mg/mL 1
• Use an in-line filter during administration 1

Onset of Action and Clinical Expectations

The antiarrhythmic effect typically becomes apparent 20-30 minutes after IV administration 2, 1. However, most conversions to sinus rhythm occur after 6-8 hours and often require at least 1 gram total dose 1. This delayed onset makes amiodarone less appropriate as a first-line agent unless the patient is clinically stable 1.

Critical Monitoring Requirements

Continuous Monitoring Mandatory

• ECG monitoring: Heart rate, AV conduction abnormalities, PR interval, QRS duration, and QT prolongation 1
• Blood pressure: Hypotension occurs in 16-26% of patients receiving IV amiodarone 1
• Heart rate: Bradycardia develops in 4.9% of patients, regardless of dose 1

When to Reduce or Stop Infusion

• If bradycardia or heart block develops, discontinue the infusion or reduce the rate immediately 1
• If heart rate decreases by 10 beats per minute, reduce the infusion rate 1
• Monitor for second- or third-degree heart block, which represents an absolute contraindication to continued therapy without pacemaker support 1

Relative Contraindications Requiring Extreme Caution

IV amiodarone should be used with extreme caution and is relatively contraindicated in the following situations unless the arrhythmia is immediately life-threatening and no safer alternatives exist: 1

• Baseline heart rate <60 bpm (especially <57 bpm) 1
• Systolic blood pressure <100 mmHg 1
• Moderate or severe left ventricular dysfunction 1
• Second- or third-degree heart block without a pacemaker 1

High-Risk Drug Interactions

• Concomitant rate-control medications (beta-blockers, calcium channel blockers, digoxin) create additive effects and significantly increase bradycardia risk 1
• Reduce digoxin dose by 50% when starting amiodarone, as digoxin levels predictably double 1, 3
• Reduce warfarin dose by one-third to one-half and monitor INR at least weekly for the first 6 weeks, as interaction effects don't peak until 7 weeks 1, 3

Alternative Agents for Hemodynamically Stable Wide-Complex Tachycardia

Given amiodarone's delayed onset and potential for hypotension/bradycardia, consider these alternatives first in stable patients: 1

• Procainamide: 20-50 mg/min until arrhythmia suppression, hypotension develops, QRS widens by ≥50%, or cumulative dose of 17 mg/kg is reached 1
• Lidocaine: Initial IV dose of 1-1.5 mg/kg when amiodarone is unavailable 1
• Beta-blockers or calcium channel blockers may be better tolerated for rate control 1

Electrical Cardioversion Priority

If the patient becomes hemodynamically unstable at any point during pharmacologic therapy, immediate electrical cardioversion should be prioritized over continued drug administration. 1

Transitioning to Oral Therapy

When converting from IV to oral amiodarone, base the oral dose on duration of IV therapy: 4

• IV therapy <1 week: 800-1,600 mg oral daily 4
• IV therapy 1-3 weeks: 600-800 mg oral daily 4
• IV therapy >3 weeks: 400 mg oral daily 4

The extremely long half-life (average 58 days, range 15-100 days) creates significant overlap between IV and oral dosing 1, 3.

Common Pitfalls to Avoid

• Do not use normal saline or lactated Ringer's as diluent—only D5W 1
• Do not exceed 2 mg/mL concentration in peripheral lines 1
• Do not forget to adjust digoxin and warfarin doses when initiating amiodarone 1, 3
• Do not administer to patients with baseline bradycardia unless pacemaker is in place or situation is immediately life-threatening 1
• Patients must not consume grapefruit or grapefruit juice during therapy, as it inhibits CYP3A-mediated metabolism and increases plasma levels 1