Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Isoniazid is a key medicine against tuberculosis: it blocks the bacteria from building mycolic acids, the waxy components of their cell wall. It is used together with other antibiotics to treat active tuberculosis, and on its own for months to treat latent infection so it does not become active. INH is its short name.
Isoniazid gave the first known example of a gene changing how people handle a medicine. It is inactivated by the liver enzyme NAT2, and slow acetylators (two low-activity NAT2 copies, about half of people of European ancestry and fewer in East Asian populations) keep higher levels, which is linked to a higher chance of liver injury and nerve side effects; fast acetylators clear it quickly. The US FDA lists the pair as affecting safety; there is no CPIC or DPWG guideline yet. A few other genes have been studied, with weaker evidence.
Clinical guidelines that name a gene for Isoniazid. They sort people into groups by the gene copies they carry.
US FDA: NAT2. Poor Metabolizer. Data that Indicate a Potential Impact on Safety or Response.
Every published finding on gene variants and Isoniazid. Upload your DNA file to see which of these rows apply to you.
PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.
NAT2 NAT2*1, NAT2*4, NAT2*5, NAT2*6, NAT2*7, NAT2*14, NAT2*16: Level 1B · replicated. Toxicity: Drug-induced liver injury, Toxic liver disease, Tuberculosis. 33.
NAT2 NAT2*1, NAT2*4, NAT2*5, NAT2*6, NAT2*6J, NAT2*7, NAT2*7G, NAT2*14, NAT2*16, NAT2*39: Level 2A · replicated. Metabolism/PK: Tuberculosis. 13.
GSTP1 rs1695: Level 3. Toxicity: Drug-induced liver injury, Tuberculosis. 3.
ABCB1 rs1045642: Level 3. Toxicity: Tuberculosis. 3.
Studies of how quickly the body processes this medication.
Studies of how well it worked in people carrying a variant.
Studies of how much of the drug people needed or tolerated.
Studies of side effects in people carrying a variant.
Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.
More drugs from the same category
Myambutol (Antimycobacterials)
Pyrazinamide (Antimycobacterials)
Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.
Content updated September 2026.
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