NCIt definition : The fumarate salt form of ibutilide, a class III antiarrhythmic agent. Ibutilide exerts
its effect by activating a slow, inward, predominately sodium current rather than
by blocking outward potassium currents. This results in prolongation of atrial and
ventricular action potential duration and refractory periods. Ibutilide slightly decreases
the sinus rate and atrioventricular (AV) conduction and produces a dose-related prolongation
of the QT interval. (NCI05);