Weight gain after Fenbendazole in dogs

The FDA has received 27 reports of weight gain in dogs after Fenbendazole. That is 0.5% of all reports for this medicine, compared with 0.6% across reports for all dog medicines.

27Reports

52%Marked serious

7.4%Recovered

11%Died or euthanised

38 daysTypical onset

How soon it started

Same day

0 0.0%

1–2 days

3 15%

3–7 days

1 5.0%

1–4 weeks

5 25%

Over a month

11 55%

How the animals did

Recovered

2 7.4%

Still unwell when reported

5 19%

Euthanised

3 11%

Not known

17 63%

Problems reported at the same time

Didn't work as expected

10 37%

Didn't stop worms

10 37%

Diarrhea

8 30%

Didn't prevent heartworm

7 26%

Vomiting

6 22%

Cough

4 15%

Weakness

4 15%

Limb non-weight bearing

4 15%

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 weight gain in dogs?: 27 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 38 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).

Weight gain with similar medicines

Weight gain after Pyrantel + Sarolaner (Simparica Trio) 31 reports · 0.1% of its reports
Weight gain after Febantel + Praziquantel + Pyrantel (Drontal Plus) 31 reports · 0.5% of its reports

All reported side effects of Fenbendazole in dogs · Medicines most reported with weight gain