Weakness after Fenbendazole in dogs

The FDA has received 146 reports of weakness in dogs after Fenbendazole. That is 2.5% of all reports for this medicine, compared with 1.4% across reports for all dog medicines, so it is reported unusually often with this medicine.

146Reports

46%Marked serious

12%Recovered

28%Died or euthanised

1 daysTypical onset

How soon it started

Same day

25 33%

1–2 days

18 24%

3–7 days

14 19%

1–4 weeks

12 16%

Over a month

6 8.0%

How the animals did

Recovered

17 12%

Still unwell when reported

35 24%

Died

27 18%

Euthanised

14 9.6%

Not known

53 36%

Problems reported at the same time

73 50%

63 43%

56 38%

44 30%

40 27%

24 16%

23 16%

15 10%

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 weakness in dogs?: 146 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 1 day 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).

Weakness with similar medicines

Weakness after Pyrantel + Sarolaner (Simparica Trio) 352 reports · 0.7% of its reports
Weakness after Febantel + Praziquantel + Pyrantel (Drontal Plus) 50 reports · 0.7% of its reports
Weakness after Pyrantel 118 reports · 2.5% of its reports
Weakness after Praziquantel + Pyrantel 79 reports · 2.1% of its reports

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