Amiodarone: The experience of the past decade

Abstract

Amiodarone is an effective agent for treating troublesome supraventricular and some serious ventricular arrhythmias. It is particularly effective for paroxysmal atrial fibrillation, supraventricular arrhythmias associated with the Wolff-Parkinson-White syndrome, and in the suppression of ventricular arrhythmias complicating hypertrophic cardiomyopathy. Its place in the treatment of arrhythmias during acute myocardial infarction is still uncertain but it was effective in several American series of patients with refractory ventricular tachycardia or fibrillation. With the increased use of amiodarone side effects are being reported increasingly often, particularly in the United States and Britain, and both the place of the drug and measures to prevent these unwanted effects need reassessment. Evidence is growing of the value of assays of plasma concentrations of amiodarone and desethylamiodarone. At present there is a rough 'therapeutic range' of 0.5 to 1.5 mg/l, which corresponds in most patients with efficacy in the absence of any substantial side effects. Plasma drug concentrations may also help identify patients with decreased bioavailability who have low plasma concentrations and may require an increased dose. The ratio of amiodarone to the desethyl metabolite may help to identify those patients who are not complying with treatment. Plasma concentrations are, however, most useful in determining the minimum effective maintenance dose when coupled with the information from clinical evaluation or ambulatory electrocardiographic monitoring or both. The drug may be being given for a serious or life threatening arrhythmia but that should not blind the physician to the fact that higher doses that are warranted carry an increased morbidity.