Selected Antimicrobial Information – Equine

Metronidazole [Equine]

Restriction Status



Species Usage Dose

For susceptible infections
  • 15-25mg/kg PO q6-8h (extra-label use)
  • 10mg/kg IV q6-8h (extra-label use)
For clostridial enterocolitis in foals 15mg/kg PO q8-12h; lower doses (10mg/kg PO or IV q12h) recommended for neonates (<14d old) (extra-label use)

Brand Name(s)



Metronidazole is a bactericidal, concentration-dependent nitroimidazole antibiotic with a narrow spectrum of activity against anaerobes and also protozoa. It distributes widely through the body, including into the central nervous system. Elimination is via hepatic metabolism, and inactive metabolites are excreted in the urine.

Acceptable Uses

  • Treatment of clostridial myositis/myonecrosis.
  • Treatment of clostridial enterocolitis.
  • As part of broad-spectrum coverage for treatment of polymicrobial infections with a suspected or culture-confirmed anaerobic component, such as pleuropneumonia or metritis.
  • Topical treatment of thrush (Fusobacterium necrophorum).

Unacceptable Uses

  • Aerobic infections.

Formulations Available within the OSU Pharmacy

  • Metronidazole 250mg tablets
  • Metronidazole 500mg tablets
  • Metronidazole 25mg/ml oral suspension
  • Metronidazole 50mg/ml oral suspension
  • Metronidazole 100mg/ml oral suspension
  • Metronidazole 5mg/ml injectable suspension


  • Higher doses have occasionally been linked to anorexia, ataxia, and depression.


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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.