Ibutilide Dosing for Atrial Fibrillation and Flutter Conversion
The recommended dose of ibutilide for converting atrial fibrillation or flutter is 1 mg IV administered over 10 minutes, which may be repeated once with a second 1 mg dose if the arrhythmia persists 10 minutes after completion of the first infusion. 1, 2, 3
Standard Dosing Protocol
Standard adult dosing (≥60 kg):
- First dose: 1 mg IV over 10 minutes
- If arrhythmia persists 10 minutes after completion of first infusion, administer second dose of 1 mg IV over 10 minutes
Weight-based dosing (<60 kg):
- First dose: 0.01 mg/kg IV over 10 minutes
- If arrhythmia persists 10 minutes after completion of first infusion, administer second dose of 0.01 mg/kg IV over 10 minutes 2
Efficacy and Timing
Ibutilide demonstrates different efficacy rates depending on the type of arrhythmia:
- More effective for atrial flutter (conversion rates 48-63%) than atrial fibrillation (conversion rates 25-38%) 1, 3
- Conversion typically occurs within 30 minutes of starting the infusion, with most conversions (70%) occurring during this timeframe 3
- Latest conversion observed was at 90 minutes after the start of infusion 3
Pre-administration Requirements
Before administering ibutilide:
- Check serum potassium and magnesium levels (must be within normal range) 2
- Ensure QTc interval is <440 msec 2, 3
- Establish continuous cardiac monitoring 2
- Have resuscitation equipment immediately available 2
Monitoring and Safety
- Monitor patients continuously during infusion and for at least 4 hours after administration due to risk of torsades de pointes 1, 2
- Risk of torsades de pointes is approximately 1.2-4% 2
- Risk of nonsustained ventricular tachycardia is approximately 1.8-6.7% 2
- Women are more susceptible to proarrhythmic effects than men (5.6% vs. 3%) 2
Contraindications
Avoid ibutilide in patients with:
- Very low ejection fraction
- Prolonged QT interval (uncorrected QT >440 ms)
- Severe aortic stenosis
- Recent acute coronary syndrome (<30 days)
- NYHA Class III and IV heart failure
- Systolic blood pressure <100 mmHg 2
Clinical Considerations
- Ibutilide is equally effective in patients below and above 65 years of age 3
- Efficacy is higher in patients with more recent onset of arrhythmia (42-50% for <30 days vs. 16-31% for chronic arrhythmias) 3
- Approximately 40% of patients remain recurrence-free at 400-500 days after acute treatment, usually with chronic prophylactic treatment 3
- Ibutilide can facilitate electrical cardioversion and decrease energy requirements if pharmacological cardioversion fails 2
By following this dosing protocol and monitoring guidelines, ibutilide can be an effective option for rapid conversion of atrial fibrillation and flutter in appropriate patients, with atrial flutter showing higher conversion rates than atrial fibrillation.