Amiodarone has been unique among antiarrhythmic agents introduced into the United States. Its clinical use has been almost entirely "compassionate use" as a last resort for life-threatening ventricular arrhythmias resistant to approved agents and often to other investigational agents. Placebo-controlled trials or simultaneous direct comparisons with standard agents did not take place before approval by the Food and Drug Administration (FDA) because they were not supported by the pharmaceutical industry. During this period of clinical use, amiodarone came to be considered to be so potent as to be in a class by itself in regard to therapeutic efficacy and in...