A comparative study on the metabolism of isonicotinic acid hydrazide and of isonicotinolylhydrazionmethanesulphonic acid in the rat.

The discovery of the antituberculous activity of isonicotinic acid hydrazide (isoniazid) has stimu- lated work intended to find new derivatives equally or more active, but less toxic than isoni- azid itself. As reported in a previous paper (Ceriotti and Franceschini, 1953), we found that N'-isonicotinoylhydrazinomethanesulphonic acid* (INHM) had these advantages. During study the activity of this drug, a discrepancy was observed between the in vitro and the in vivo activity The in vitro activity of was somewhat lower, the in vivo higher, when compared with a corresponding amount of isoniazid. This interesting feature could be ascribed either to a difference in the mode of action of the two drugs or to a difference of their behaviour when introduced into the organism. two drugs quantitative qualitative in their metabolism.