What patients are indicated for a bolus dose of amiodarone and what are the administration guidelines for both intravenous (IV) and oral routes?

Amiodarone Bolus Dosing: Indications and Administration

Indications for Bolus Amiodarone

Amiodarone bolus is indicated for life-threatening ventricular arrhythmias (VF/pulseless VT) unresponsive to defibrillation and vasopressor therapy, as well as hemodynamically unstable ventricular tachycardia requiring immediate treatment. 1

Primary Indications:

• Cardiac arrest with VF/pulseless VT: Administer 300 mg IV bolus when rhythm remains refractory to CPR, defibrillation, and epinephrine 1
• Hemodynamically unstable ventricular tachycardia: Use when immediate rhythm control is needed 1
• Recurrent, life-threatening ventricular tachyarrhythmias: In patients who are refractory to conventional antiarrhythmic drugs 1, 2

Secondary Indications:

• Atrial fibrillation with rapid ventricular response causing acute heart failure or hemodynamic instability, particularly in patients with structural heart disease where other agents are contraindicated 1, 3
• Supraventricular tachycardia in acute heart failure when cardioversion is being considered 1

Intravenous Bolus Administration

For Life-Threatening Arrhythmias (VF/Pulseless VT):

Initial bolus: 300 mg IV/IO over 10 minutes 1, 4

• If VF/pulseless VT persists, give second bolus of 150 mg IV/IO 1, 4
• Follow with continuous infusion: 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours 1, 4
• Maximum infusion rate should not exceed 30 mg/min 4, 5

For Hemodynamically Stable Ventricular Arrhythmias:

Loading dose: 150 mg IV bolus over 10 minutes 1

• May repeat 150 mg bolus every 10-30 minutes if necessary 1
• Follow with maintenance infusion as above 1, 4

Critical Administration Details:

• Must use volumetric infusion pump (drop counters can underdose by up to 30%) 4, 5
• Administer through central venous catheter whenever possible 4, 5
• Use in-line filter during administration 4, 5
• Concentrations >2 mg/mL require central line for infusions >1 hour (peripheral administration causes high phlebitis rates) 4
• Dilute in D5W only (glass or polyolefin bottles for infusions >2 hours) 4, 5
• Do not use PVC containers for mixing due to incompatibility 4

Common Pitfalls:

• Hypotension occurs in 26% of patients receiving IV amiodarone; ensure vasopressor has been given first in cardiac arrest 1, 2
• Bradycardia and AV block can occur; monitor continuously 1, 6
• Avoid rapid infusion rates >30 mg/min as this has caused hepatocellular necrosis and acute renal failure leading to death 4

Oral Loading Dose Administration

For Ventricular Arrhythmias:

Loading: 800-1,600 mg/day in divided doses 1, 7

• Continue until total of 10 grams administered 1, 7
• Then reduce to maintenance dose of 200-400 mg/day 1, 7
• Typical loading duration is approximately 1-2 weeks 8

For Atrial Fibrillation:

Loading: 600-800 mg/day in divided doses 1, 7

• Continue until total of 10 grams administered 1, 7
• Then reduce to maintenance dose of 200 mg/day 1, 7
• May use higher initial dosing or IV loading in unstable inpatients 1

Oral Administration Considerations:

• Full antiarrhythmic effect takes days to weeks despite adequate serum levels 7
• Avoid grapefruit juice as it inhibits CYP3A4 metabolism and increases amiodarone levels 4, 5
• Monitor for bradycardia, QT prolongation, and GI upset (nausea, constipation) 1, 7

Transitioning from IV to Oral

Conversion Dosing Based on IV Duration:

• <1 week IV: Start 800-1,600 mg oral daily 7, 4, 5
• 1-3 weeks IV: Start 600-800 mg oral daily 7, 4, 5
• >3 weeks IV: Start 400 mg oral daily 7, 4, 5

Monitoring During Transition:

• Watch for breakthrough arrhythmias in first 6 hours after IV discontinuation 7
• Monitor ECG closely for QT prolongation, bradycardia, and heart block 7
• Check blood pressure as hypotension may occur with loading doses 7
• Clinical monitoring is particularly important in elderly patients 4, 5

Management of Breakthrough Arrhythmias:

If tachycardia recurs <6 hours after transition:

• Assess hemodynamic stability first 7
• If unstable, consider resuming IV at 1 mg/min or immediate cardioversion 7
• Check electrolytes (potassium, magnesium) and correct abnormalities 7
• Monitor for contraindications (QT prolongation, heart block, bradycardia) before additional dosing 7