Selected Antimicrobial Information – Companion Animal

Metronidazole [Companion]

Restriction Status



Species Usage Dose
Cats Label dose 10-15mg/kg PO or IV q12h
For serious anaerobic infections 25 – 50 mg/kg PO or IV q12h
For enteritis caused by Clostridium difficile 62.5mg/cat PO q12h for 5d
For metronidazole benzoate 25 mg/kg PO q12h
Dogs Label dose 10-15mg/kg PO q12h

Brand Name(s)



Metronidazole is a bactericidal, concentration-dependent nitroimidazole antibiotic with a narrow spectrum of activity against anaerobes and protozoa. It is not effective against aerobes. It distributes widely throughout the body, including into bone and the central nervous system. Elimination is via hepatic metabolism, and both active drug and inactive metabolites are excreted in urine and feces.

Acceptable Uses

  • Treatment of enteric or systemic anaerobic infections, including sepsis with a suspected or culture-confirmed anaerobic component.
  • Treatment of giardiasis and other protozoal enteric infections, sometimes used in combination with fenbendazole.
  • Surgical prophylaxis against anaerobes, often used in combination with an antimicrobial with aerobic coverage.

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


  • Metronidazole has a bitter taste and owners should be warned about excessive salivation after administration.
  • High doses of metronidazole are neurotoxic in dogs and cats, which display central vestibular signs.
  • Used to treat giardiasis (at 10-15mg/kg PO q12h) in combination with fenbendazole.


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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.