Selected Antimicrobial Information – Farm Animal

Isoniazid* [Farm Animal]

Restriction Status

*Isoniazid has a “selectively use” status within the OSU-VMC. Therefore, this antibiotic should NOT be used as empirical or first-line treatment. Rather, it should only be used when other agents are inappropriate or ineffective, and culture/sensitivity results indicate that isoniazid is effective against the pathogen.


Species Usage Dose
Camelids Label dose 10 mg/kg PO q24h, a 30d treatment regimen has been recommended in camelids
Cattle Label dose 10 mg/kg PO q24h
Small Ruminants Label dose 10 mg/kg PO q24h
Swine Label dose No labeled dose.

Brand Name(s)



Isoniazid is a time-dependent anti-mycobacterial antimicrobial with in vitro bactericidal activity against rapidly-dividing mycobacteria in the growing phase, and bacteriostatic activity against slowly-dividing mycobacteria. In vivo efficacy is uncertain. Because of the importance of isoniazid as a treatment for human tuberculosis, use of isoniazid is controversial in animals. Pharmacokinetics are poorly understood in animals, but in humans, isoniazid is widely distributed, including into the CNS and caseous material. Elimination is through hepatic metabolism, and inactive metabolites are excreted into the urine.

Current Uses within OSU-VMC

  • Treatment of Actinomyces sp., Actinobacillus sp., or chronic abscesses.

Contraindicated Uses

  • Has been suggested for management of Johne’s Disease (Mycobacterium avium subsp. paratuberculosis) in animals of particular financial or sentimental value. This is not recommended since it is not a curative treatment.

Illegal Uses

  • None

Formulations Available within the OSU Pharmacy

  • Isoniazid 300mg tablet


  • Commonly used to treat lumpy jaw (Actinomyces bovis) and wooden tongue (Actinobacillus lignieresii).


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OSU VMC Antimicrobial Use Guidelines Copyright © 2018 by The Ohio State University College of Veterinary Medicine is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.