What is the protocol for preparing and administering an amiodarone infusion in a patient with potential liver or kidney disease, or a history of thyroid disease?

Amiodarone Infusion Protocol

Administer amiodarone as 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/24 hours), using a central venous catheter for concentrations >2 mg/mL. 1, 2, 3

Standard Infusion Protocol for Life-Threatening Ventricular Arrhythmias

Loading Phase

• Initial bolus: 150 mg IV diluted in 100 mL D5W infused over 10 minutes 2, 3
• First maintenance infusion: 1 mg/min for 6 hours (360 mg total) 1, 2, 3
• Second maintenance infusion: 0.5 mg/min for remaining 18 hours (540 mg total) 1, 2, 3
• Total 24-hour dose: Approximately 1,050 mg (do not exceed 2,100 mg/24 hours due to increased hypotension risk) 3

Cardiac Arrest Protocol (VF/Pulseless VT)

• First dose: 300 mg IV/IO bolus over 10 minutes if unresponsive to defibrillation and epinephrine 2
• Second dose: 150 mg IV/IO if rhythm persists 2

Breakthrough Arrhythmias

• Supplemental dosing: 150 mg IV in 100 mL D5W over 10 minutes for breakthrough VF or hemodynamically unstable VT 3

Critical Preparation and Administration Requirements

Concentration and Vascular Access

• Concentrations >2 mg/mL require mandatory central venous catheter to prevent severe peripheral vein phlebitis (occurs in 16% of patients) 2, 3
• For infusions >1 hour, do not exceed 2 mg/mL concentration unless using central line 2, 3
• Concentrations >3 mg/mL are associated with high incidence of peripheral vein phlebitis 3

Equipment and Compatibility

• Must use volumetric infusion pump (drop counter sets can underdose by up to 30% due to altered surface properties) 3
• Use in-line filter during administration 3
• Administer in glass or polyolefin bottles containing D5W for infusions >2 hours 3
• Do not use evacuated glass containers (may cause precipitation) 3
• No light protection needed during administration 3

Absolute Contraindications

Do not administer amiodarone without a functioning pacemaker in patients with: 2

• Second- or third-degree AV block 2
• Sick sinus syndrome 2
• Severe sinus node dysfunction 2

Additional contraindications:

• Acute inflammatory lung disease 2
• Heart transplant recipients 2

Special Populations and Dose Modifications

Hepatic Dysfunction

• Use with extreme caution in patients with liver disease 2
• Higher concentrations and faster infusion rates than recommended have resulted in hepatocellular necrosis and acute renal failure leading to death 3
• Amiodarone-induced hepatitis can occur, particularly with chronic use 4

Renal Dysfunction

• No specific dose adjustment required for IV amiodarone (primarily hepatically metabolized) 3
• However, renal phospholipidosis causing progressive kidney dysfunction has been reported, though rare 5

Thyroid Disease History

• Amiodarone contains iodine and causes thyroid dysfunction in 10% of patients 4
• Type 2 amiodarone-induced thyrotoxicosis can occur (elevated free T4, suppressed TSH) 6
• Monitor thyroid function closely but do not withhold in acute life-threatening arrhythmias 6, 4

Monitoring During Infusion

Cardiovascular Monitoring

• Hypotension occurs in 16% of IV patients - monitor blood pressure continuously 2
• Bradycardia occurs in 4.9% of IV patients 2
• Monitor for AV block, heart block, and QT prolongation 2
• Symptomatic bradycardia requiring pacemaker support occurs in approximately 6% 7

Infusion Site Monitoring

• Inspect peripheral IV sites frequently for phlebitis 2, 3
• Switch to central access if phlebitis develops 3

Critical Drug Interactions Requiring Immediate Action

Digoxin

• Reduce digoxin dose by 50% when starting amiodarone (levels will predictably double) 2, 7

Warfarin

• Reduce warfarin dose by 33-50% and monitor INR at least weekly (interaction peaks at 7 weeks) 2, 7

QT-Prolonging Drugs

• Avoid concomitant use without expert consultation 2

Duration of Therapy

• Maintenance infusion of 0.5 mg/min can be continued for 2-3 weeks regardless of age, renal function, or left ventricular function 3
• Limited experience exists for IV amiodarone >3 weeks 3
• Infusions should be discontinued after 6-24 hours and need for further arrhythmia management reassessed 1

Common Pitfalls to Avoid

• Never use drop counter infusion sets - they underdose by up to 30% 3
• Never exceed 30 mg/min initial infusion rate 3
• Never infuse concentrations >2 mg/mL peripherally for >1 hour 3
• Do not administer in patients with high-grade AV block without pacemaker backup 2
• Recognize that higher doses (>2,100 mg/24h) significantly increase hypotension risk 3