Isonicotinyl Hydrazide or Isoniazid has for some years now been used in conjunction with other compounds in the treatment of pulmonary tuberculosis. During this treatment certain workers (Robitzek et al., 1952) noted the development of a state of euphoria in their patients. Since Isoniazid was known to exert toxic effects on nervous tissue (Gammen et al., 1953) the hypothesis was made that the substance might be capable of producing an elevation of mood by direct action on the central nervous system. Acting on this hypothesis, Salzer and Lurie (1953) treated a group of patients suffering from various depressive conditions with Isoniazid given orally in the dosage of 50 mgm. t.d.s. for one week. If no toxic effects occurred the dosage was raised to 100 mgm. t.d.s. for a further two weeks, while in a few cases only higher doses were given. These workers maintained this level of dosage in order to avoid the advent of toxic side effects. Their results, which will be discussed later in this paper, led them to the conclusion that isoniazid had a specific therapeutic effect upon certain depressive disorders.

The object of this study, arising out of the work mentioned, was to carry out an initial survey of the effects of isoniazid on the affective component of various depressive states. If any demonstrable therapeutic action had been noted a larger, controlled, and more systematic study would have been undertaken but in view of the results obtained this further project has now been abandoned.