Chapter 1: Amiodarone and Dronedaroner

OVERVIEW

AMIODARONE

Amiodarone is designated as a class III antiarrhythmic drug based on the Vaughan Williams classification. Consistent with other class III antiarrhythmic drugs, amiodarone blocks potassium channels to delay phase 3 repolarization.¹ However, amiodarone possesses electrophysiological (EP) effects similar to all four classes of antiarrhythmic drugs by (1) blocking sodium channels (class I effect)², (2) potent nonselective, noncompetitive β-adrenergic receptor blockade (class II effect)³, and (3) antagonizing calcium channel activity (class IV effect). As a result, amiodarone prolongs action potential duration (APD), resulting in prolongation of the effective refractory period.¹

Amiodarone is indicated for the treatment of life-threatening, recurrent, refractory ventricular arrhythmias,⁴ including recurrent ventricular fibrillation (VF)⁵ and recurrent hemodynamically unstable ventricular tachycardia (VT).⁶ In addition to these indications, amiodarone is commonly used for treatment of atrial fibrillation (AF) particularly in patients with heart failure.^{7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, and 24} According to the 2011 consensus guidelines of the American Heart Association (AHA) and the American College of Cardiology (ACC) for the management of atrial fibrillation,²⁵ amiodarone can also be used for cardioversion of recent-onset AF.²⁶ Amiodarone is not only beneficial in terminating AF, but it can be effective at maintaining normal sinus rhythm (NSR) and preventing AF recurrence.^{27, 28, 29, 30, 31, 32, 33, 34, 35, 36, and 37} The Canadian trial of AF (CTAF) reported that amiodarone reduced the incidence of recurrent AF compared to other antiarrhythmic drugs (35% vs. 63%, respectively).²⁹ Additional studies have demonstrated that amiodarone is effective at preventing AF following cardiovascular and cardiothoracic surgeries.^29,31

Dosing

Amiodarone dosing varies depending on the clinical indication. Table 1-1 summarizes the dosing recommendations for amiodarone according to AHA recommendations, 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death, and its focused update in 2011 on the management of atrial fibrillation. Amiodarone is commercially available as 100 and 200 mg oral tablets or as 50 mg/mL for IV administration.