The use of metronidazole in adult dogs with acute onset, uncomplicated, diarrhoea



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PICO question

In adult, non-geriatric, dogs with acute onset (<7 days duration) uncomplicated diarrhoea does the addition of metronidazole to a supportive care protocol such as dietary modification or probiotics (excluding other antimicrobials) reduce the time to resolution of diarrhoea compared to supportive care protocols alone?


Clinical bottom line

Category of research question


The number and type of study designs reviewed

Four studies were included in this appraisal. Two prospective, double blinded, placebo controlled clinical trials, one prospective treatment trial and one retrospective longitudinal observational study

Strength of evidence


Outcomes reported

One study found a shortened duration of clinical signs (by 1.5 days; p = 0.04) in the metronidazole treated group compared to control. However, a separate study found no significant difference between control and metronidazole groups in the regards to resolution of clinical signs.

One study demonstrated a long standing (>28 day) negative impact of metronidazole treatment on gut microbiome with no difference in time to resolution of clinical signs when compared with faecal matter transplant


The current evidence for the superiority of metronidazole compared to supportive treatment alone is weak and at this time there is no evidence-based rationale for its use in cases of uncomplicated, acute, canine diarrhoea. Furthermore, the negative implications of metronidazole on the intestinal microbiome have been found to be long standing (>28 days as a minimum) and should not be discounted by the prescribing clinician


How to apply this evidence in practice

The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.

Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.


Open Access Peer Reviewed


Chaitman, J., Ziese, A., Pilla, R., Minamoto, Y., Blake, A.B., Guard, B.C., Isaiah, A., Lidbury, J.A., Steiner, J.M., Unterer, S. & Suchodolski, J.S. (2020). Faecal Microbial and Metabolic Profiles in Dogs With Acute Diarrhoea Receiving Either Faecal Microbiota Transplantation or Oral Metronidazole. Frontiers in Veterinary Science. 7(192). DOI:

Duboc, H., Rajca, S., Rainteau, D., Benarous, D., Maubert, M-A., Quervain, E., Thomas, G., Barbu, V., Humbert, L., Despras, G., Bridonneau, C., Dumetz, F., Grill, J-P., Masliah, J., Beaugerie, L., Cosnes, J., Chazouillères, O., Poupon, R., Wolf, C., Mallet, J-M., Langella, P., Trugnan, G., Sokol, H. & Seksik, P. (2013). Connecting dysbiosis, bile-acid dysmetabolism and gut inflammation in inflammatory bowel diseases. Gut. 62(4), 531–539. DOI:

Jensen, A.P. & Bjørnvad, C.R. (2019). Clinical effect of probiotics in prevention or treatment of gastrointestinal disease in dogs: A systematic review. Journal of Veterinary Internal Medicine. 33(5), 1849–1864. DOI:

Langlois, D., Koenigshof, A.M. & Mani, R. (2020). Metronidazole treatment of acute diarrhoea in dogs: A randomized doubled blinded placebo-controlled clinical trial. Journal of Veterinary Internal Medicine. 34(1), 98–104. DOI:

Rau, S.E., Barber, L.G. & Burgess, K.E. (2010). Efficacy of maropitant in the prevention of delayed vomiting associated with administration of doxorubicin to dogs. Journal of Veterinary Internal Medicine. 24(6), 1452–1457. DOI:

Shmalberg, J., Montalbano, C., Morelli, G. & Buckley, G.J. (2019). A Randomized Double Blinded Placebo-Controlled Clinical Trial of a Probiotic or Metronidazole for Acute Canine Diarrhea. Frontiers in Veterinary Science. 6(163). DOI:

Singleton, D.A., Noble, P.J.M., Sánchez-Vizcaíno, F., Dawson, S., Pinchbeck, G.L., Williams, N.J., Radford, A.D. & Jones, P.H. (2019). Pharmaceutical Prescription in Canine Acute Diarrhoea: A Longitudinal Electronic Health Record Analysis of First Opinion Veterinary Practices. Frontiers in Veterinary Science. 6(218). DOI:

Vol. 6 No. 4 (2021): The fourth issue of 2021

Section: Knowledge Summaries

Categories :  Small Animal  /  Dogs  /  Cats  /  Rabbits  /  Production Animal  /  Cattle  /  Sheep  /  Pig  /  Equine  /  Exotics  /