What is the recommended Amiodarone (antiarrhythmic medication) infusion protocol?

Amiodarone Infusion Protocol

The standard amiodarone infusion protocol consists of a 150 mg IV bolus over 10 minutes, followed by 1 mg/min for 6 hours (360 mg), then 0.5 mg/min for 18 hours (540 mg), with a maximum total dose of 2.2 g over 24 hours. 1, 2, 3

Loading Phase

• Initial bolus: Administer 150 mg IV over 10 minutes for rapid loading 1, 2, 3
• This bolus can be repeated for breakthrough ventricular tachycardia (VT) or ventricular fibrillation (VF), mixed in 100 mL D5W and infused over 10 minutes 3
• The initial bolus should not exceed an infusion rate of 30 mg/min 3

Maintenance Infusion - Two-Phase Approach

Early Maintenance (First 6 Hours)

• Infusion rate: 1 mg/min for 6 hours, delivering 360 mg total 1, 2, 3
• This phase provides continued loading while minimizing hemodynamic effects 2

Late Maintenance (Next 18 Hours)

• Infusion rate: 0.5 mg/min for 18 hours, delivering 540 mg total 1, 2, 3
• This completes the first 24-hour dosing period with a total of approximately 1050 mg (including the initial bolus) 1, 3

Extended Maintenance Beyond 24 Hours

• Continue 0.5 mg/min infusion for up to 2-3 weeks if needed 1, 3
• The infusion rate may be increased to achieve effective arrhythmia suppression, but do not exceed 2.2 g total in the first 24 hours 3
• Mean daily doses above 2100 mg are associated with increased risk of hypotension 3

Critical Administration Requirements

Delivery Method

• Must use a volumetric infusion pump - drop counter sets can underdose by up to 30% due to altered surface properties 3
• Administer through a central venous catheter whenever possible 3
• Use an in-line filter during administration 3

Concentration Guidelines

• For infusions >1 hour: do not exceed 2 mg/mL concentration unless using a central line 3
• Concentrations >3 mg/mL are associated with high incidence of peripheral vein phlebitis 3
• Use concentrations of 1-6 mg/mL via central venous catheter 1, 3

Solution Preparation

• Mix in D5W only 3
• Use glass or polyolefin bottles for infusions >2 hours 3
• Do not use evacuated glass containers for admixing due to incompatibility risk 3
• PVC tubing is acceptable (all clinical trials used PVC), though amiodarone adsorbs to it and leaches plasticizers 3

Mandatory Monitoring During Infusion

Continuous Monitoring Required

• Cardiac rhythm - watch for bradycardia and AV block 1, 2
• Blood pressure - hypotension is the most common adverse effect (26% incidence) 1, 2, 4
• Heart rate - monitor for symptomatic bradycardia 2

Critical Adverse Effects to Watch

• Hypotension: Most common serious adverse event, occurring in 26% of patients; no clear dose-response relationship 4
• Bradycardia: Can be symptomatic and require intervention 2, 5
• AV block: Monitor continuously for conduction disturbances 1, 2
• Hepatocellular necrosis and acute renal failure: Can occur with loading infusions at higher concentrations and faster rates than recommended 3

Special Clinical Contexts

Ventricular Arrhythmias

• This protocol is specifically indicated for sustained monomorphic VT not associated with angina, pulmonary edema, or hypotension 6
• For drug-refractory polymorphic VT, use the same protocol (150 mg over 10 minutes, then 1 mg/min for 6 hours, then 0.5 mg/min) 6
• Efficacy is dose-dependent: higher doses (1000 mg/24h) show better event rate reduction than lower doses (125 mg/24h) 4

Atrial Fibrillation

• Cardioversion typically occurs after 6-8 hours and often requires ≥1000 mg total dose 1
• Conversion rates: 34-69% with bolus-only regimens, 55-95% with bolus plus continuous infusion 1
• Even with high-dose rapid infusions, pharmacological conversion within 12 hours is modest (51% in one study) 7

Patients with Structural Heart Disease

• Amiodarone is particularly valuable when Class IC agents are contraindicated 1, 2
• Use with extreme caution in moderate-severe left ventricular dysfunction - two patients with severe LV dysfunction developed significant hypotension during loading 2, 8
• May cause negative inotropic effects in patients with moderate or severe LV failure 1

Absolute Contraindications

• Severe sinus node dysfunction 2
• Marked sinus bradycardia 2
• Second- or third-degree AV block without pacemaker 2
• Heart transplant recipients 2

Critical Drug Interaction Warning

• Do not combine with procainamide or other QT-prolonging drugs without expert consultation 2
• Amiodarone has numerous drug interactions due to effects on multiple ion channels 1
• Extremely long half-life (IV: 9-36 days) leads to accumulation and delayed adverse effects 1

Common Pitfalls to Avoid

• Never use drop counter infusion sets - they will underdose by up to 30% 3
• Do not infuse concentrations >2 mg/mL through peripheral veins for infusions >1 hour 3
• Do not exceed 30 mg/min initial infusion rate - faster rates increase risk of hepatocellular necrosis 3
• Watch for hypotension especially in patients with severe LV dysfunction - this is the most common serious adverse event 5, 8, 4
• Have defibrillator immediately available when treating cardiac arrest 2