Didn't work as expected after Fenbendazole in dogs

562 reports to the FDA describe didn't work as expected in dogs given Fenbendazole. That is 9.6% of all reports for this medicine, compared with 13% across reports for all dog medicines.

562Reports
57%Marked serious
12%Recovered
7.7%Died or euthanised
28 daysTypical onset
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How soon it started

Same day
19 6.3%
1–2 days
14 4.7%
3–7 days
26 8.7%
1–4 weeks
107 36%
Over a month
134 45%

How the animals did

Recovered
68 12%
Recovered with lasting effects
1 0.2%
Still unwell when reported
177 31%
Died
29 5.2%
Euthanised
14 2.5%
Not known
273 49%

Problems reported at the same time

Didn't stop worms
117 21%
Vomiting
71 13%
Diarrhea
67 12%
Death
44 7.8%
Loss of appetite
42 7.5%
Lethargy
37 6.6%
Dehydration
22 3.9%
Drug administration duration too long
21 3.7%

Age of the animals

Under 1 year
259
1–3 years
136
4–7 years
71
8–11 years
29
12+ years
13

About this medicine

Fenbendazole treats intestinal worms and some other parasites.

Questions owners ask

Can Fenbendazole cause didn't work as expected in dogs?
562 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 28 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 work as expected with similar medicines

All reported side effects of Fenbendazole in dogs · Medicines most reported with didn't work as expected