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Isoniazid is a prescription antimycobacterial medicine used against susceptible Mycobacterium tuberculosis. Current tablets contain 100 mg or 300 mg. Active tuberculosis is treated with isoniazid together with other active tuberculosis medicines to reduce development of drug resistance.
read more about isoniazid ...Isoniazid inhibits synthesis of mycolic acids, which are components of the mycobacterial cell wall. At therapeutic concentrations, it is bactericidal against actively growing intracellular and extracellular Mycobacterium tuberculosis.
Isoniazid is used for susceptible forms of active tuberculosis as part of a multidrug regimen and for preventive treatment of tuberculosis infection under appropriate clinical criteria. Before preventive therapy begins, active tuberculosis is excluded.
For active tuberculosis, the usual adult oral dose is 5 mg per kg up to 300 mg daily in one dose, or 15 mg per kg up to 900 mg two or three times weekly as part of a multidrug regimen. Children use weight-based dosing. For preventive therapy, the current tablet label lists 300 mg daily for adults over 30 kg and 10 mg per kg up to 300 mg daily for infants and children.
Isoniazid carries a boxed warning for severe and sometimes fatal hepatitis. Other serious concerns include peripheral neuropathy, severe skin reactions, cerebellar syndrome, seizures, blood-cell disorders, and drug interactions. Patients with previous isoniazid-related liver injury or acute liver disease do not use the medicine.
Isoniazid is used for susceptible tuberculosis as part of combination treatment and for preventive tuberculosis therapy under appropriate criteria.
No. Active tuberculosis requires other active tuberculosis medicines with isoniazid to reduce drug resistance.
The labeled daily dose is 5 mg per kg up to 300 mg in one dose.
Yes. The boxed warning concerns severe and sometimes fatal hepatitis.
Clinical Overview of Latent Tuberculosis Infection. https://www.cdc.gov/tb/hcp/clinical-overview/latent-tuberculosis-infection.html. Date Accessed October 5, 2026.
Isoniazid. https://www.ncbi.nlm.nih.gov/books/NBK557617/. Date Accessed October 5, 2026.
Isoniazid. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. https://www.ncbi.nlm.nih.gov/books/NBK548754/. Date Accessed October 5, 2026.
Isoniazid: MedlinePlus Drug Information. https://www.medlineplus.gov/druginfo/meds/a682401.html. Date Accessed October 5, 2026.
ISONIAZID Tablets Prescribing Information. https://www.dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=03bf3bd5-64f9-4491-89fd-96c5c10d0129. Date Accessed October 5, 2026.