Isonicotinic acid hydrazide , metabolic

According to Zini (Zl), prolonged oral treatment with isonicotinic acid hydrazide interfered with tryptophan metabolism, probably by inhibiting kynureninase activity, which catalyzes the synthesis of anthra-nilic acid from kynurenine. 

Davis, R. B., Alexander, C. S. and Adicoff, A., Metabolic studies in carcinoid syndrome observations on use of a-methyldopa, isonicotinic acid hydrazide, and selective tryptophan deficiency. Metabolism 10, 1035 (1961). 

Isoniazid (INH), a hydrazide derivative of isonicotinic acid, is the bactericidal drug of choice for tuberculosis. INH is well known for its propensity to cause hepatitis with chronic use. Acute isoniazid overdose is a common cause of drug-indued seizures and metabolic acidosis. 

Isoniazide is an amide derivative with a major potential for antimicrobial efficacy but also general toxicity, which is an obstacle to its practical application as a microbicide for the protection of materials. It has been used as a bacteriostat, primarily to inhibit the proliferation of tubercle bacteria, the cell wall of which is easily passed by Isoniazide molecules. Within the cytoplasm the isonicotinic add hydrazide is split enzymatically to isonicotinic acid, which remains in the cell cytoplasm and as an antimetabolite of the cytoplasmic nicotinic acid disturbs the cell s metabolism. 

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