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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. Because of its Class III antiarrhythmic activity, there should not be concomitant administration of Class Ia and Class III agents. Ibutilide is marketed as Corvert by Pfizer. Administration resulted in successful heart rhythm control in 31-44% of patients within 90 minutes, with sustained polymorphic ventricular tachycardia in 0.9-2.5% of patients. It appears to show better results in atrial flutter as compared to atrial fibrillation. == Mechanism of action == Unlike most other Class III antiarrhythmic drugs, ibutilide does not produce its prolongation of action potential via blockade of cardiac delayed rectifier of potassium current, nor does it have a sodium-blocking, antiadrenergic, and calcium blocking activity that other Class III agents possess. Thus it is often referred as a “pure” Class III antiarrhythmic drug. Ibutilide, like other class III antiarrhythmic drugs, blocks delayed rectified potassium current. It does have action on the slow sodium channel and promotes the influx of sodium through these slow channels. Although potassium current seems to play a role, their interactions are complex and not well understood.〔Howard, P.A., Ibutilide: An antiarrhythmic agent for the treatment of atrial fibrillation or flutter. Annals of Pharmacotherapy, 1999. 33(1): p. 38-47. (PMID9972384 )〕 Ibutilide’s unique mechanism works by an activation of a specific inward sodium current, thus producing its therapeutic response in which a prolonged action potential increases myocytes’ cardiac refractoriness in case of atrial fibrillation and flutter. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ibutilide」の詳細全文を読む スポンサード リンク
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