How do I convert an Amiodarone (antiarrhythmic medication) intravenous (IV) drip to an oral dose?

Amiodarone IV to Oral Conversion Protocol

When converting from intravenous amiodarone to oral amiodarone, the dosing should be based on the duration of prior IV therapy, with 800-1600 mg daily for patients who received IV amiodarone for less than one week. 1

Conversion Protocol Based on Duration of IV Therapy

The optimal dose for transitioning from IV to oral amiodarone depends on the duration of previous IV administration and considers the bioavailability of oral amiodarone (approximately 50%).

Specific Conversion Guidelines:

• IV amiodarone < 1 week: Convert to 800-1600 mg oral amiodarone daily in divided doses 1
• IV amiodarone 1-3 weeks: Convert to 600-800 mg oral amiodarone daily in divided doses 1
• IV amiodarone > 3 weeks: Convert to 400 mg oral amiodarone daily 1

Loading Dose and Maintenance Phase

After the initial conversion, follow this protocol:

1. Loading phase: Continue the initial oral dose until a total loading dose of 10 g has been administered 1
2. Maintenance phase:
   • For ventricular arrhythmias: 200-400 mg daily 1
   • For atrial fibrillation: 200 mg daily 1

Clinical Considerations

• Bioavailability: Oral amiodarone has variable bioavailability (22-86%), which necessitates higher oral doses compared to IV doses 2
• Onset of action: While IV amiodarone has rapid onset (<30 minutes), oral amiodarone has a delayed onset of 1-3 weeks to achieve full effect 1
• Overlap strategy: Recent research suggests that providing an overlap of IV and oral amiodarone does not significantly decrease early tachyarrhythmia recurrence rates 3

Monitoring Recommendations

During the transition period, monitor for:

• Bradycardia: Common during transition (9-13% incidence) 3
• Hypotension: May occur in 13-20% of patients during transition 3
• QT prolongation: Regular ECG monitoring is essential 1
• Drug interactions: Particularly with warfarin and digoxin 1

Common Pitfalls to Avoid

• Failure to adjust for duration of IV therapy: Longer IV treatment requires lower oral doses due to tissue accumulation
• Inadequate loading dose: Insufficient loading can lead to breakthrough arrhythmias
• Overlooking drug interactions: Amiodarone potentiates warfarin and increases digoxin levels
• Grapefruit juice consumption: Should be avoided during oral amiodarone therapy as it increases plasma levels 4

Special Populations

• Patients with structural heart disease: Amiodarone is relatively safe compared to other antiarrhythmics in patients with structural heart disease or depressed left ventricular function 5
• Elderly patients: Clinical monitoring is particularly important when transitioning elderly patients from IV to oral therapy 4

Remember that amiodarone has a very long half-life (up to 100 days after long-term treatment), which contributes to its unique pharmacokinetic profile and dosing considerations 2.