What is the recommended intravenous amiodarone loading and maintenance dosing protocol for an adult, and what monitoring and contraindications should be considered?

How to Give Amiodarone Drip

For life-threatening ventricular arrhythmias (VF or hemodynamically unstable VT), administer IV amiodarone as a 150 mg bolus over 10 minutes, followed by 1 mg/min for 6 hours, then 0.5 mg/min maintenance, with continuous ECG and blood pressure monitoring throughout. 1, 2

Standard Dosing Protocol

The FDA-approved regimen delivers approximately 1000 mg over the first 24 hours in three stages 1:

• Rapid loading: 150 mg in 100 mL D5W infused over 10 minutes 3, 1
• Early maintenance: 1 mg/min for 6 hours (360 mg) 3, 1
• Late maintenance: 0.5 mg/min thereafter (540 mg over remaining 18 hours) 3, 1

For breakthrough episodes of VF or hemodynamically unstable VT during maintenance infusion, repeat the 150 mg bolus over 10 minutes 1.

Critical Administration Requirements

Vascular Access and Equipment

• Use central venous access whenever possible, as peripheral vein phlebitis occurs frequently with concentrations >2 mg/mL 2, 4
• Administer through a volumetric infusion pump with an in-line filter 4
• Never infuse faster than the recommended rate, as hypotension is rate-dependent rather than dose-dependent 4

Mandatory Monitoring

Continuous monitoring is non-negotiable 2, 4:

• ECG monitoring for heart rate, AV conduction abnormalities, PR interval, QRS duration, and QT prolongation 2
• Continuous arterial blood pressure monitoring throughout loading and maintenance phases 4
• If heart rate decreases by 10 beats per minute, reduce the infusion rate immediately 2

Absolute Contraindications

Do not administer amiodarone if 1:

• Second- or third-degree AV block without a functioning pacemaker 1, 2
• Marked sinus bradycardia without pacemaker support 1, 4
• Cardiogenic shock 1
• Known hypersensitivity to amiodarone or iodine 1

Relative Contraindications Requiring Extreme Caution

Amiodarone should be used with extreme caution (or avoided unless immediately life-threatening with no alternatives) in 3, 2:

• Heart rate <60 bpm 3
• Systolic blood pressure <100 mm Hg 3, 4
• Moderate or severe left ventricular failure 3, 4

Managing Common Adverse Effects

Hypotension (occurs in 16% of patients)

At the first sign of hypotension 4, 5:

1. Stop the infusion or immediately reduce the infusion rate 4
2. Administer fluid bolus if hypotension persists 4
3. Consider vasopressor drugs, positive inotropic agents, or volume expansion as needed 1
4. Review and adjust concomitant medications that lower blood pressure (beta-blockers, calcium channel blockers, digoxin) 4

Patients with severe left ventricular dysfunction are at highest risk for significant hypotension during loading 6.

Bradycardia (occurs in 4.9% of patients)

If bradycardia develops 2, 1:

• Reduce the infusion rate or discontinue immediately 1
• Monitor for progression to second- or third-degree heart block, which requires discontinuation without pacemaker support 2
• Bradycardia risk is present regardless of dose administered 2

Critical Drug Interactions to Address Before Starting

Digoxin

Reduce digoxin dose by 50% when starting amiodarone, as digoxin levels predictably double 2, 4

Warfarin

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 2

Concomitant Rate-Control Agents

Beta-blockers, calcium channel blockers, or digoxin create additive effects and significantly increase bradycardia risk 2. Consider dose reduction or temporary discontinuation before amiodarone loading.

Important Clinical Caveats

• Grapefruit juice is absolutely prohibited during amiodarone therapy, as it inhibits CYP3A metabolism and increases plasma levels 2, 4
• Amiodarone is a substrate for CYP3A and CYP2C8, and inhibits p-glycoprotein and CYP1A2, CYP2C9, CYP2D6, and CYP3A, creating numerous drug interactions 1
• The drug has an extremely long half-life (average 58 days, range 15-100 days), resulting in significant overlap between IV and oral dosing 2
• Women are at higher risk for amiodarone-associated bradycardia requiring permanent pacemaker implantation 2

When to Consider Alternatives

For atrial fibrillation rate control, beta-blockers or nondihydropyridine calcium channel blockers are first-line agents (Class I recommendation), with amiodarone reserved for refractory cases when conventional measures fail 2. These alternatives have more predictable pharmacokinetics and lower toxicity profiles 2.

For hemodynamically unstable patients with ventricular arrhythmias, electrical cardioversion should be considered rather than pharmacologic therapy 2.