Isoniazid

Isoniazid is an antimicrobial drug used mainly to prevent and treat tuberculosis. Activated inside mycobacteria, it inhibits enzymes needed to synthesize mycolic acids in the cell wall.

KatG: KatG is a mycobacterial catalase-peroxidase enzyme that activates isoniazid. This enzyme converts the prodrug into forms that can inhibit mycolic-acid synthesis.
Latent tuberculosis: Latent tuberculosis is infection with Mycobacterium tuberculosis without symptoms of active disease or contagiousness. Isoniazid is used in preventive regimens to reduce the risk of progression to active disease.
Isoniazid-induced liver injury: Isoniazid-induced liver injury is hepatic damage associated with isoniazid, ranging from enzyme elevations to severe hepatitis. Liver injury is a major safety concern during preventive or curative treatment.
Gerhard Domagk: Gerhard Domagk was a German pathologist who discovered the antibacterial effects of the sulfonamide drug Prontosil. His work helped spur the search for synthetic drugs against tuberculosis that led to isoniazid.
InhA: InhA is an enoyl-acyl carrier protein reductase required for mycolic-acid synthesis in mycobacteria. Isoniazid-derived compounds inhibit this enzyme, disrupting cell-wall production.
Tuberculosis: Tuberculosis is an infectious disease caused by members of the Mycobacterium tuberculosis complex, usually affecting the lungs. Isoniazid is a core drug in many regimens for this disease.
Peripheral neuropathy: Peripheral neuropathy is damage to nerves outside the brain and spinal cord, causing symptoms such as numbness, tingling, or weakness. Isoniazid can cause this adverse effect, especially when pyridoxine is deficient.
Jörgen Lehmann: Jörgen Lehmann was a Swedish physician who introduced para-aminosalicylic acid as a tuberculosis treatment. His clinical work formed part of the early combination-therapy context in which isoniazid emerged.
Mycolic acid: Mycolic acids are long-chain fatty acids that form a distinctive layer of the mycobacterial cell envelope. Their synthesis is the pathway that isoniazid blocks.
Rifampicin: Rifampicin is an antibiotic that inhibits bacterial DNA-dependent RNA polymerase and is a key tuberculosis drug. It is commonly combined with isoniazid in active-tuberculosis treatment.

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