What is the protocol for initiating an amiodarone (antiarrhythmic medication) infusion?

Amiodarone Infusion Initiation Protocol

Initiate amiodarone infusion with a 150 mg IV bolus over 10 minutes, followed by 1 mg/min for 6 hours, then 0.5 mg/min for the remaining 18 hours, with a maximum total dose of 2.2 g over 24 hours. 1, 2, 3, 4

Loading Phase

Rapid Loading Bolus:

• Administer 150 mg IV over 10 minutes as the initial loading dose 1, 2, 3, 4
• Mix the 150 mg bolus in 100 mL of D5W 4
• Do not exceed an initial infusion rate of 30 mg/min 4

Early Maintenance Infusion:

• Follow immediately with 1 mg/min for 6 hours (total 360 mg) 1, 2, 3, 4

Late Maintenance Infusion:

• Continue at 0.5 mg/min for the remaining 18 hours (total 540 mg) 1, 2, 3, 4
• This provides approximately 1000 mg total over the first 24 hours 4

Administration Requirements

Vascular Access:

• Use a central venous catheter for concentrations >2 mg/mL 3, 4
• For peripheral access, do not exceed 2 mg/mL concentration for infusions >1 hour to prevent severe phlebitis 3, 4
• Concentrations >3 mg/mL are associated with high incidence of peripheral vein phlebitis 4

Equipment and Solutions:

• Must use a volumetric infusion pump (drop counter sets can underdose by up to 30%) 4
• Use an in-line filter during administration 4
• Administer in glass or polyolefin bottles containing D5W for infusions >2 hours 4
• Do not use evacuated glass containers for admixing (may cause precipitation) 4

Breakthrough Arrhythmia Management

Supplemental Dosing:

• For breakthrough VF or hemodynamically unstable VT, give 150 mg supplemental bolus 4
• Mix in 100 mL D5W and infuse over 10 minutes 4
• This minimizes hypotension risk 4

Cardiac Arrest Dosing (VF/Pulseless VT):

• Give 300 mg IV/IO bolus if unresponsive to defibrillation and epinephrine 3
• May give second 150 mg bolus if rhythm persists 3

Critical Monitoring Requirements

Continuous Monitoring:

• Heart rate and rhythm (continuous cardiac monitoring mandatory) 2, 3
• Blood pressure (hypotension occurs in 16% of IV patients) 2, 3
• ECG for QT prolongation 2, 3

Watch for Dose-Related Adverse Effects:

• Hypotension (16% incidence) - most common adverse effect 3, 5
• Bradycardia (4.9% incidence) 3
• AV block and heart block 3
• Phlebitis at infusion site 3, 4

Important Precautions and Contraindications

High-Risk Situations:

• Severe left ventricular dysfunction: Use with extreme caution, as hypotension risk is significantly increased 1, 6
• Two patients with severe LV dysfunction developed significant hypotension during loading in clinical studies 6

Absolute Contraindications:

• Second- or third-degree AV block without pacemaker 3
• Sick sinus syndrome without pacemaker 3
• Severe sinus node dysfunction without pacemaker 3
• Heart transplant recipients 3

Drug Interactions:

• Avoid concomitant QT-prolonging medications 2
• Amiodarone has numerous drug interactions due to effects on multiple ion channels 2

Dosing Limits and Duration

Maximum Dosing:

• Do not exceed 2.2 g total over 24 hours 2, 3, 4
• Mean daily doses >2100 mg associated with increased hypotension risk 4
• Maintenance infusion up to 0.5 mg/min can continue for 2-3 weeks 4

Rate Adjustment:

• May increase maintenance infusion rate to achieve effective arrhythmia suppression 4
• Limited experience exists for IV amiodarone >3 weeks 4

Common Pitfalls to Avoid

• Never use drop counter infusion sets - they underdose by up to 30% 4
• Never exceed 2 mg/mL concentration in peripheral veins for infusions >1 hour 3, 4
• Never infuse faster than 30 mg/min initially - risk of hepatocellular necrosis and acute renal failure 4
• Never skip continuous cardiac monitoring - bradycardia and AV block can occur acutely 2, 3
• Be aware that amiodarone has an extremely long half-life (IV: 9-36 days), leading to accumulation and delayed adverse effects 2