How to Start Intravenous Amiodarone Infusion
Standard Loading Protocol
For life-threatening arrhythmias, administer 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
Initial Bolus Administration
- Give 150 mg IV over 10 minutes for immediate arrhythmia suppression 1, 2, 3
- The bolus may be repeated in 10-30 minutes if necessary for persistent arrhythmias 1
- Antiarrhythmic effect begins within 30 minutes of IV administration 1
Maintenance Infusion Phases
Early maintenance (first 6 hours):
- Infuse at 1 mg/min (delivers 360 mg over 6 hours) 1, 2, 3
- This phase provides continued loading while minimizing hypotension risk 2
Late maintenance (next 18 hours):
- Reduce to 0.5 mg/min (delivers 540 mg over 18 hours) 1, 2, 3
- Continue this rate for up to 2-3 weeks if needed 3
Breakthrough Arrhythmia Management
- For recurrent VF or hemodynamically unstable VT during infusion, give supplemental 150 mg boluses mixed in 100 mL D5W over 10 minutes 3
- Multiple supplemental doses may be needed, but monitor cumulative 24-hour dose 3
Critical Administration Requirements
Infusion Setup
- Use a volumetric infusion pump (never use drop counters, as they can underdose by up to 30%) 3
- Administer through a central venous catheter whenever possible 3
- Use an in-line filter during administration 3
- For concentrations >2 mg/mL, a central line is mandatory to prevent peripheral vein phlebitis 3
Solution Preparation
- Mix in D5W only (dextrose 5% in water) 3
- Use glass or polyolefin bottles for infusions >1 hour 3
- Do not use evacuated glass containers (may cause precipitation) 3
- Concentrations ≤2 mg/mL can be given peripherally; >2 mg/mL require central access 3
Mandatory Monitoring During Infusion
Cardiovascular Monitoring
- Continuous ECG monitoring for heart rate, rhythm, and QT interval 2, 4
- Continuous blood pressure monitoring (hypotension occurs in 16% of patients) 1, 4
- Watch for bradycardia (occurs in 4.9% with IV administration) 4
- Monitor for AV block development 1, 2
Critical Warning Signs to Stop or Reduce Infusion
- Hypotension - most common adverse effect, may require rate reduction or pressors 1, 3, 5
- Bradycardia - if heart rate drops by ≥10 bpm, reduce infusion rate 4
- Second or third-degree heart block - absolute contraindication without pacemaker 4
- Severe QT prolongation - though torsades is rare with amiodarone 1
Important Contraindications and Precautions
Relative Contraindications
- Pre-existing bradycardia (HR <60 bpm) without pacemaker - use extreme caution 4
- Severe left ventricular dysfunction - higher risk of hypotension 6
- Concomitant use of other rate-slowing drugs (beta-blockers, calcium channel blockers, digoxin) increases bradycardia risk 4
Drug Interactions Requiring Immediate Dose Adjustments
- Reduce digoxin dose by 50% when starting amiodarone (levels predictably double) 4
- Reduce warfarin dose by 30-50% and check INR within 3-5 days 7, 4
- Avoid other QT-prolonging medications 2
Transition to Oral Therapy
Timing Based on IV Duration
- <1 week IV: Start 800-1,600 mg oral daily 1, 7
- 1-3 weeks IV: Start 600-800 mg oral daily 1, 7
- >3 weeks IV: Start 400 mg oral daily 1
Loading Strategy
- Continue oral loading until total of 10 g administered, then reduce to maintenance dose of 200-400 mg daily 1, 7
- Begin oral dosing while IV infusion continues due to amiodarone's extremely long half-life (26-107 days) 2, 4
Special Clinical Situations
Atrial Fibrillation
- Same loading protocol applies 1, 2
- Conversion typically occurs after 6-8 hours and often requires ≥1,000 mg total dose 2
- Particularly valuable in patients with structural heart disease or LV dysfunction where class IC drugs are contraindicated 2, 8