Ibutilide

IBUTILIDE

Ibutilide, like dofetilide, slows cardiac depolarization by blockade of the rapid component (I_Kr) of the delayed rectifier potassium current. Activation of slow inward sodium current has also been suggested as an additional mechanism of action potential prolon-gation. After intravenous administration, ibutilide is rapidly cleared by hepatic metabolism. The metabolites are excreted by the kidney. The elimination half-life averages 6 hours.

Intravenous ibutilide is used for the acute conversion of atrial flutter and atrial fibrillation to normal sinus rhythm. The drug is more effective in atrial flutter than atrial fibrillation, with a mean time to termination of 20 minutes. The most important adverse effect is excessive QT-interval prolongation and torsades de pointes. Patients require continuous ECG monitoring for 4 hours after ibutilide infusion or until QT_c returns to baseline.