1. Contact your veterinarian immediately.
  2. It is helpful if you can tell the veterinarian the body weight of your animal and the doses administered.
  3. Your veterinarian may instruct you to induce vomiting, however, do not induce vomiting unless instructed to. Never induce vomiting in an animal that is having seizures.
  4. As other toxins and diseases cause similar signs it is important that your pet is examined.
  5. Bring the drug your pet has ingested, together with its label or package insert to enable the vet to confirm the dose of drug ingested.


Flagyl, Metric 21, Protostat, Flagyl ER.




The onset of signs is strongly dependent on the dosage and duration of treatment. Typically animals show signs within days of commencing a course of medication, but doses of metronidazole above 250mg/kg will result in acute signs of toxicity shortly after administration of the drug.

  • Inappetence, anorexia (not eating)
  • Vomiting
  • Depression
  • Vertical darting eye movements (vertical nystagmus)
  • Tilting the head to one side
  • Joint/paw knuckling
  • Uncoordinated gait (ataxia), inability to walk
  • Disorientation
  • Muscle tremors/spasms
  • Seizures
  • Rigidity or stiffness
  • Low heart rate (bradycardia)


The exact mechanism of toxicity is unclear but the type of neurological effects caused by this toxicity suggests involvement of certain parts of the brain. Metronidazole has also been shown to cause mutations in some species so it is not recommended in pregnant animals.


If your pet has ingested the drugs within the last 2 hours, your vet may induce vomiting in your pet if it is stable enough. Other procedures may include gastric lavage or administration of multiple doses of activated charcoal to bind any remaining circulating toxins in the system.

Your pet may require hospitalisation for close monitoring of its vital signs like heart rate, respiratory rate and blood pressure, and for supportive care, which may involve intravenous fluids and symptomatic treatment of clinical signs.


Fitzgerald KT (2006) Metronidazole.In:Small Animal Toxicology. 2nd Eded. Peterson ME & Talcott PA. USA: Elsevier Saunders.

Plumb DC (2011) Plumb’s Veterinary Drug Handbook 7th Edn. Iowa, USA:Wiley-Blackwell