Ibutilide Dosage for Atrial Fibrillation Conversion
The recommended dosage of ibutilide for converting atrial fibrillation to normal sinus rhythm is 1 mg IV administered over 10 minutes, followed by a second 1 mg dose after waiting for 10 minutes if the first dose is ineffective. 1
Standard Dosing Protocol
- Initial dose: 1 mg IV administered over 10 minutes 1
- Follow-up dose: If atrial fibrillation persists 10 minutes after completion of the first infusion, a second 1 mg dose should be administered over 10 minutes 1, 2
- The maximum total dose should not exceed 2 mg 2
Efficacy and Timing
- Conversion to normal sinus rhythm typically occurs within 30 minutes of starting the infusion in approximately 70% of patients who respond 2, 3
- Ibutilide is more effective for atrial flutter (conversion rates 48-76%) than for atrial fibrillation (conversion rates 25-51%) 2, 4
- Recent-onset arrhythmias (less than 30 days duration) respond better to ibutilide than chronic arrhythmias 2, 5
Safety Considerations and Monitoring
- ECG and hemodynamic monitoring is mandatory during administration and for at least 4 hours afterward due to risk of QT prolongation and torsades de pointes 1
- QT interval and T-U wave abnormalities should be closely monitored during and after administration 1
- The risk of polymorphic ventricular tachycardia/torsades de pointes is approximately 3-4% of patients 1
- Nonsustained ventricular tachycardia occurs in 2.7-6.7% of patients, while sustained polymorphic ventricular tachycardia occurs in approximately 1.7% 3, 5
Contraindications
Ibutilide should be avoided in patients with:
- QT prolongation 1
- Hypokalemia 1
- Severe left ventricular hypertrophy 1
- Low ejection fraction 1
- Systolic blood pressure <100 mmHg 1
- Recent acute coronary syndrome (within 30 days) 1
- NYHA Class III and IV heart failure 1
- Severe aortic stenosis 1
Special Populations
- In elderly patients (≥65 years), standard dosing can be used with similar efficacy (54-63% conversion rate), but with careful monitoring for adverse effects 6
- For post-cardiac surgery atrial fibrillation/flutter, doses of 0.5-1 mg have shown efficacy (42-44% for atrial fibrillation, 61-78% for atrial flutter) 2
Clinical Pearls
- Patients should be adequately hydrated before ibutilide administration 1
- Have emergency equipment readily available, including defibrillator and medications to treat potential arrhythmias 1
- Ibutilide will slow the ventricular rate in addition to its cardioversion effects 1
- The elimination half-life ranges from 2-12 hours, requiring continued monitoring after administration 3
- In comparative studies, ibutilide has shown superior efficacy to procainamide and sotalol for conversion of both atrial fibrillation and flutter 3, 4