Didn't work as expected after Fipronil in cats

38 reports to the FDA describe didn't work as expected in cats given Fipronil. That is 7.6% of all reports for this medicine, compared with 8.7% across reports for all cat medicines.

38Reports
7.9%Marked serious
7.9%Recovered
0.0%Died or euthanised
29 daysTypical onset
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How soon it started

Same day
1 3.0%
1–2 days
0 0.0%
3–7 days
9 27%
1–4 weeks
7 21%
Over a month
16 48%

How the animals did

Recovered
1 2.6%
Recovered with lasting effects
2 5.3%
Still unwell when reported
7 18%
Not known
28 74%

Problems reported at the same time

Didn't stop fleas
27 71%
Itching
6 16%
Hair loss
2 5.3%
Unpalatable
1 2.6%
Skin rash or irritation
1 2.6%
Application site reaction
1 2.6%
Lethargy
1 2.6%
Urinary tract infection
1 2.6%

Age of the animals

Under 1 year
3
1–3 years
7
4–7 years
9
8–11 years
7
12+ years
6

About this medicine

Fipronil kills fleas and ticks (spot-on).

Questions owners ask

Can Fipronil cause didn't work as expected in cats?
38 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 29 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 Fipronil in cats · Medicines most reported with didn't work as expected