Didn't stop worms after Fenbendazole in cats

The FDA has received 33 reports of didn't stop worms in cats after Fenbendazole. That is 12% of all reports for this medicine, compared with 1.8% across reports for all cat medicines, so it is reported unusually often with this medicine.

33Reports
48%Marked serious
18%Recovered
0.0%Died or euthanised
21 daysTypical onset
SponsoredWorried about your pet? Ask a veterinarian online, 24/7

How soon it started

Same day
2 8.3%
1–2 days
0 0.0%
3–7 days
2 8.3%
1–4 weeks
13 54%
Over a month
7 29%

How the animals did

Recovered
6 18%
Still unwell when reported
21 64%
Not known
6 18%

Problems reported at the same time

Drug administration error
6 18%
Vomiting
1 3.0%
Unpalatable
1 3.0%
Flatulence
1 3.0%
Loose stool
1 3.0%
Rectal bleeding
1 3.0%
Rectal prolapse
1 3.0%
Inappropriate defecation
1 3.0%

Age of the animals

Under 1 year
24
1–3 years
6
4–7 years
0
8–11 years
1
12+ years
0

About this medicine

Fenbendazole treats intestinal worms and some other parasites.

Questions owners ask

Can Fenbendazole cause didn't stop worms in cats?
33 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 21 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 worms with similar medicines

All reported side effects of Fenbendazole in cats · Medicines most reported with didn't stop worms