Tarry or black stool after Metronidazole in dogs

58 reports to the FDA describe tarry or black stool in dogs given Metronidazole. That is 1.9% of all reports for this medicine, compared with 0.1% across reports for all dog medicines, so it is reported unusually often with this medicine.

58Reports

74%Marked serious

12%Recovered

43%Died or euthanised

7 daysTypical onset

How soon it started

Same day

7 15%

1–2 days

6 13%

3–7 days

11 24%

1–4 weeks

14 30%

Over a month

8 17%

How the animals did

Recovered

7 12%

Still unwell when reported

21 36%

Died

3 5.2%

Euthanised

22 38%

Not known

5 8.6%

Problems reported at the same time

46 79%

36 62%

33 57%

27 47%

25 43%

24 41%

20 34%

14 24%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Metronidazole treats some bacterial and parasitic gut infections.

Questions owners ask

Can Metronidazole cause tarry or black stool in dogs?: 58 reports link the two, but a report alone does not prove the medicine was the cause: other illnesses, other medicines or coincidence can be involved. Your vet can judge it for your animal.
How soon after a dose was it reported?: In half of the reports with dates, it started within 7 days of the first dose.
What should I do?: Don't give another dose until you've spoken to your vet, and keep the packaging so you can tell them the product and dose. Your vet can also report it to the FDA (or you can, through the manufacturer or FDA form 1932a).

Tarry or black stool with similar medicines

Tarry or black stool after Amoxicillin + Clavulanate (Clavamox) 26 reports · 0.5% of its reports
Tarry or black stool after Cefovecin (Convenia) 26 reports · 0.7% of its reports
Tarry or black stool after Enrofloxacin (Baytril) 26 reports · 0.7% of its reports

All reported side effects of Metronidazole in dogs · Medicines most reported with tarry or black stool