Timing of Oral Amiodarone After IV
Begin oral amiodarone while the IV infusion is still running, typically starting when patients have received approximately 4 grams IV or after 1-3 weeks of IV therapy, with an initial oral dose of 600-800 mg daily in divided doses. 1
Transition Strategy
When to Start Oral Therapy
Start oral amiodarone during the ongoing IV infusion rather than waiting for IV discontinuation, as amiodarone has an extremely long half-life (15-100 days, average 58 days) that necessitates overlapping therapy. 1
For patients who have received IV amiodarone for less than 1 week, initiate oral dosing at 800-1600 mg daily. 1
For patients who have received IV amiodarone for 1-3 weeks, start with 600-800 mg oral daily in divided doses. 1
The FDA label indicates that patients may be transferred to oral amiodarone during or after IV treatment, with most requiring IV therapy for 48-96 hours before stabilization. 2
Loading Phase Protocol
Continue the oral loading dose (600-800 mg daily in divided doses) until a cumulative total of 10 grams has been administered, which typically takes 1-2 weeks depending on the daily dose used. 1
While loading orally, maintain the IV infusion at 0.5 mg/min for patients who have received approximately 4 grams IV over an extended period. 1
After completing the 10-gram oral loading, transition to maintenance dosing of 200-400 mg daily. 1
Critical Monitoring During Transition
Cardiovascular Parameters
Implement continuous telemetry monitoring for at least 24 hours after IV discontinuation, with heart rate checks every 4-6 hours initially, then at least daily. 1
Obtain daily ECGs to assess QT interval and detect heart block during the transition period. 1
Monitor for bradycardia (occurs in 1-3% on oral therapy vs 4.9% on IV), hypotension (16% with IV), and AV block. 1, 3
If heart rate decreases by 10 beats per minute during transition, reduce the infusion rate. 3
Drug Interaction Management
Reduce digoxin dose by 50% immediately when starting oral amiodarone, as amiodarone predictably doubles digoxin levels. 1, 3
Reduce warfarin dose by 30-50% and check INR within 3-5 days, as amiodarone significantly increases anticoagulation effects; monitor INR at least weekly for the first 6 weeks since interaction effects don't peak until 7 weeks. 1, 3
Reduce doses of other rate-control medications (beta-blockers, calcium channel blockers) as amiodarone's rate-control effect develops. 1
Managing Breakthrough Arrhythmias
Assessment Algorithm
If breakthrough tachycardia occurs less than 6 hours after IV discontinuation and first oral dose, evaluate hemodynamic stability first. 1
Check for QT prolongation, heart block, or bradycardia which may contraindicate additional amiodarone. 1
Review electrolyte status, particularly potassium and magnesium levels. 1
Intervention Options
If hemodynamically unstable, consider resuming IV amiodarone at 1 mg/min for 6 hours, then 0.5 mg/min, or proceed directly to cardioversion if immediate rhythm control is needed. 1
Monitor heart rate, blood pressure, and ECG closely for at least 4 hours after administration of any additional amiodarone. 1
Common Pitfalls to Avoid
Do not wait to start oral therapy until after IV is completely discontinued - the extremely long half-life requires overlapping administration to maintain therapeutic levels. 1
Do not forget to adjust interacting medications proactively - waiting for adverse effects from drug interactions (elevated INR, digoxin toxicity) is dangerous. 1, 3
Avoid peripheral IV administration when possible, as concentrations >2 mg/mL frequently cause phlebitis; use a central line and in-line filter. 3
Do not administer amiodarone to patients consuming grapefruit or grapefruit juice, as it inhibits CYP3A-mediated metabolism and increases plasma levels. 3