Metronidazole toxicity in dogs: signs and treatment
9-year-old crossbreed with chronic liver disease, on high-dose metronidazole for chronic diarrhoea for 5 weeks. It acutely develops generalised ataxia, head tilt, vertical nystagmus and hypermetria. It is alert.
What is the most appropriate management?
chevron_right Show answer and explanation
A. Continue metronidazole and add meclizine for the vertigo
If the signs are caused by metronidazole, continuing it makes them worse. Meclizine only relieves the nausea of vestibular syndrome.
B. Urgent MRI and cerebrospinal fluid analysis before withdrawing the drug
With such a clear history, the first step is to withdraw metronidazole. Imaging is reserved for cases that do not improve within a few days.
C. Stop metronidazole and give diazepam for a few days
Correct. Diazepam markedly shortens recovery: in a retrospective study it fell from 1–2 weeks to 1–2 days. It is thought to act on GABA modulation in the cerebellum and vestibular system.
D. Flumazenil to reverse metronidazole's effect on the GABA receptor
Flumazenil is a benzodiazepine antagonist; it has no role in this toxicity and would block the beneficial effect of diazepam.
lightbulb Key takeaway
Metronidazole toxicity causes central vestibular and cerebellar signs (vertical nystagmus, ataxia, hypermetria) and sometimes seizures. It is dose- and time-dependent and more likely with liver disease, which reduces its clearance. Use moderate doses, adjust them in dogs with liver disease and reconsider whether metronidazole is needed in chronic diarrhoea.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.