Ibutilide – class IIIa

Ibutilide – class IIIa

Ibutilide is a class IIIa antiarrhythmic agent as per the Modernized Classification of Cardiac Antiarrhythmic Drugs [1]. The class effect is voltage dependent K+ channel blocker. Specifically, it is a HERG channel –mediated rapid K+ current (IKr) blocker.

Ibutilide increases the refractoriness of atrial and ventricular myocytes, atrioventricular (AV) node and the His-Purkinje system.

The drug has been approved for the conversion  of acute atrial flutter and atrial fibrillation. The infusion is stopped when the arrhythmia resolves or a new ventricular tachycardia develops. If the arrhythmia does not resolve with the initial dose, a repeat infusion may be given after 10 minutes [2].

Like other class III drugs, it carries the potential for QTc prolongation and risk of developing torsades de pointes. Magnesium increases efficacy and reduces QTc prolongation. Hence preloading with intravenous magnesium is desirable before setting up infusion of ibutilide [2].


  1. Ming Lei, Lin Wu, Derek A Terrar, Christopher L-H Huang. Modernized Classification of Cardiac Antiarrhythmic Drugs. Circulation. 2018 Oct 23;138(17):1879-1896.
  2. Michael W. Szymanski; Manouchkathe Cassagnol. Ibutilide. StatPearls. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.