Ibutilide Fumarate

Ibutilide is a Class III antiarrhythmic agent that is indicated for acute cardioconversion of atrial fibrillation and atrial flutter of a recent onset to sinus rhythm. It exerts its antiarrhythmic effect by induction of slow inward sodium current, which prolongs action potential and refractory period (physiology) of myocardial cells. (In Vitro) :Ibutilide fumarate is a potent IKr blocker with an EC50 value of 20 nM at +20 mV in atrial tumor myocytes (AT-1) cells.Ibutilide fumarate blocks IKr in cells expressing HERG+MDR1*1 to the same extent as cells expressing HERG alone (IC50: 22.5 nM vs 27.4 nM) . However, cells expressing MDR1*7 show a marked resistance to Ibutilide (IC50: 105.3 nM vs 27.4 nM) . (In Vivo) :Ibutilide fumarate prolongs cardiac repolarization in vitro and in vivo.Ibutilide (administered cumulatively in three doses, 0.01, 0.02 and 0.05 mg/kg i.v., each as a 10-min infusion) fumarate results in both polymorphic and monomorphic non-sustained ventricular tachycardia.