The frequency of medical reversal.

W e use the term reversal to signify the phenomenon of a new trial—superior to predecessors because of better design, increased power, or more appropriate controls—contradicting current clinical practice. In recent years, a number of such reversals have occurred. Use of hormone therapy, the class 1C antiarrhythmic agents, and the pulmonary artery catheter have decreased when trials demonstrated that they are either less effective than previously thought or harmful.