Didn't stop fleas after Fenbendazole in dogs

The FDA has received 24 reports of didn't stop fleas in dogs after Fenbendazole. That is 0.4% of all reports for this medicine, compared with 6.2% across reports for all dog medicines, so it is reported less often than average with this medicine.

24Reports

50%Marked serious

8.3%Recovered

8.3%Died or euthanised

5 daysTypical onset

How soon it started

Same day

2 11%

1–2 days

7 37%

3–7 days

1 5.3%

1–4 weeks

4 21%

Over a month

5 26%

How the animals did

Recovered

2 8.3%

Still unwell when reported

12 50%

Died

2 8.3%

Not known

8 33%

Problems reported at the same time

8 33%

7 29%

7 29%

5 21%

4 17%

4 17%

4 17%

3 13%

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 didn't stop fleas in dogs?: 24 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 5 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).

Didn't stop fleas with similar medicines

Didn't stop fleas after Pyrantel + Sarolaner (Simparica Trio) 1,757 reports · 3.3% of its reports
Didn't stop fleas after Pyrantel 25 reports · 0.5% of its reports
Didn't stop fleas after Praziquantel + Pyrantel 28 reports · 0.8% of its reports

All reported side effects of Fenbendazole in dogs · Medicines most reported with didn't stop fleas