Antibacterial agent used primarily as a tuberculostatic. It remains the treatment of choice for tuberculosis. Isoniazid (also called isonicotinyl hydrazine or INH; sold as Laniazid, Nydrazid) is an organic compound that is the first-line antituberculosis medication in prevention and treatment. First discovered in 1912 as an inhibitor of the MAO enzyme, it was first used as an antidepressant, but discontinued due to side effects. In 1951, it was later discovered that isoniazid was effective against TB. Isoniazid is never used on its own to treat active tuberculosis because resistance quickly develops.; Isoniazid is a bactericidal agent active against organisms of the genus Mycobacterium, specifically M. tuberculosis, M. bovis and M. kansasii. It is a highly specific agent, ineffective against other microorganisms. Isoniazid is bactericidal to rapidly-dividing mycobacteria, but is bacteriostatic if the mycobacterium is slow-growing.; Isoniazid is a prodrug and must be activated by bacterial catalase. It is activated by catalase-peroxidase enzyme KatG which couples the isonicotinic acyl with NADH to form isonicotinic acyl-NADH complex. This complex binds tightly to ketoenoylreductase known as InhA, thereby blocking the natural enoyl-AcpM substrate and the action of fatty acid synthase. This process inhibits the synthesis of mycolic acid required for the mycobacterial cell wall. A range of radicals are produced by KatG activation of Isoniazid, including nitric oxide, that has also been shown to be important in the action of another antimycobacterial prodrug PA824. [HMDB]


Technical grade hexachlorocyclohexane is a manufactured chemical that typically consists of the alpha, beta, delta, epsilon, and gamma isomers of hexachlorocyclohexane. It is used as an insecticide on fruit, vegetables, and forest crops and is also available as a prescription (lotion, cream, or shampoo) to treat head and body lice, and scabies. (L108)

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Isoniazid Interacts with Diseases

Isoniazid Interacts with Genes