Lymphopenia after Metronidazole in dogs

The FDA has received 100 reports of lymphopenia in dogs after Metronidazole. That is 3.2% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported unusually often with this medicine.

100Reports

81%Marked serious

15%Recovered

34%Died or euthanised

23 daysTypical onset

How soon it started

Same day

11 14%

1–2 days

11 14%

3–7 days

9 12%

1–4 weeks

8 10%

Over a month

38 49%

How the animals did

Recovered

15 15%

Still unwell when reported

38 38%

Died

11 11%

Euthanised

23 23%

Not known

13 13%

Problems reported at the same time

62 62%

62 62%

57 57%

56 56%

54 54%

42 42%

38 38%

34 34%

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 lymphopenia in dogs?: 100 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 23 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).

Lymphopenia with similar medicines

Lymphopenia after Amoxicillin + Clavulanate (Clavamox) 95 reports · 1.8% of its reports
Lymphopenia after Doxycycline 64 reports · 1.6% of its reports
Lymphopenia after Cefovecin (Convenia) 39 reports · 1.0% of its reports
Lymphopenia after Enrofloxacin (Baytril) 99 reports · 2.6% of its reports
Lymphopenia after Amoxicillin 26 reports · 1.9% of its reports

All reported side effects of Metronidazole in dogs · Medicines most reported with lymphopenia