In the dark old days of American Psychiatry, most patients were diagnosed with schizophrenia and prescribed Thorazine (chlorpromazine) or its equivalent. One of the true pioneers of rational medication treatment is Donald Klein of Columbia University, who in 1962 was a psychiatrist practicing at Hillside Hospital in New York. He and his colleague Max Fink published an early study in Archives of General Psychiatry in which they documented the responses of a variety of patients to imipramine vs. chlorpromazine. One patient in particular (diagnosed as schizophrenic) suffered an "atypical" syndrome of paroxysmal episodes of fear and agitation that would last for several minutes and then subside. He did not respond to Thorazine, but these episodes diminished on robust doses of imipramine. Klein later labeled these "paroxysmal" episodes "panic attacks," but it was not until 1980 that the concept of panic disorder gained acceptance in American psychiatry. It was in that year that David Sheehan and colleagues published a seminal article on "Endogenous Anxiety". Soon thereafter, Upjohn introduced Xanax (alprazolam), and panic disorder was rapidly transformed from an unknown disorder to one of the most commonly treated conditions in psychiatry.

Source: Sheehan DV, Ballenger J, and Jacobsen G: Treatment of endogenous anxiety with phobic, hysterical, and hypochondriacal symptoms. Archives of General Psychiatry. 1980;37:51-57.