Decreased red blood cell count after Fenbendazole in dogs

28 reports to the FDA describe decreased red blood cell count in dogs given Fenbendazole. That is 0.5% 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.

28Reports

96%Marked serious

14%Recovered

29%Died or euthanised

7 daysTypical onset

How soon it started

Same day

6 25%

1–2 days

5 21%

3–7 days

3 13%

1–4 weeks

4 17%

Over a month

6 25%

How the animals did

Recovered

4 14%

Still unwell when reported

10 36%

Died

2 7.1%

Euthanised

6 21%

Not known

6 21%

Problems reported at the same time

Decreased haemoglobin

16 57%

Decreased packed cell volume (pcv)

16 57%

13 46%

13 46%

12 43%

11 39%

11 39%

10 36%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Fenbendazole treats intestinal worms and some other parasites.

Questions owners ask

Can Fenbendazole cause decreased red blood cell count in dogs?: 28 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).

Decreased red blood cell count with similar medicines

Decreased red blood cell count after Pyrantel + Sarolaner (Simparica Trio) 28 reports · 0.1% of its reports

All reported side effects of Fenbendazole in dogs · Medicines most reported with decreased red blood cell count