Generic Name: metronidazole
Brand Name: Flagyl
Metronidazole is an antibiotic used in both human and veterinary medicine to treat a variety of disease states, including chronic diarrhea.
Toxicity often occurs from intentional dosing at levels greater than 30 mg/kg/day. While much of the literature warns of potential toxicity at doses greater than 60 mg/kg/day, there is an increasing incidence of toxicity occurring at lower doses. Beyond dosing, there seems to be a positive correlation of prolonged therapy (3 weeks and longer) and toxicosis.
Signs and symptoms of toxicity: difficulty walking, rapid eye movements, head-tilt, joint knuckling, disorientation, refusal to eat, vomiting, extreme fatigue, stiffness and seizures.
Toxic consumption: The referenced toxic threshold is 60 mg/kg/day (values listed in chart below). As previously mentioned, chronic therapy with lower doses may result in toxicosis.
Please note that these values are total daily consumption.
Pug, Boston Terrier, Poodle
Beagle, Scottish Terrier
Boxer, Cocker Spaniel
Labrador & Golden Retrievers, German Shepherd
Great Dane, St. Bernard
|1 – 10 lbs.
(0.45 – 4.6 kg)
|11 – 25 lbs.
(5 – 11.4 kg)
|26 – 40 lbs.
(11.8 – 18.2 kg)
|41 – 70 lbs.
(18.6 – 31.8 kg)
|71 – 90 lbs.
(32.3 – 40.9 kg)
|91 – 110 lbs.
(41.4 – 50 kg)
|> 27 mg||> 300 mg||> 708 mg||> 1116 mg||> 1938 mg||> 2484 mg|
– Evans J, Levesque D, Knowles K, et al. Diazepam as a treatment for metronidazole toxicosis in dogs: A retrospective case study of 21 cases. J Vet Intern Med 2003;17:304-10.
– Metronidazole. In: Plumb’s Veterinary Drugs. Tulsa (OK): Educational Concepts, L.L.C. [updated 8/14; accessed 8/14/15]. https://www.plumbsveterinarydrugs.com/#!/monograph/2566
– Papich MG. Saunders Handbook of Veterinary Drugs: Small and Large Animal. 3rd ed. St. Louis, MS: Elsevier Saunders; 2011.