Hair loss after Imidacloprid + Pyriproxyfen in cats

83 reports to the FDA describe hair loss in cats given Imidacloprid + Pyriproxyfen. That is 13% of all reports for this medicine, compared with 14% across reports for all cat medicines.

83Reports
59%Marked serious
18%Recovered
6.0%Died or euthanised
14 daysTypical onset
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How soon it started

Same day
4 8.2%
1–2 days
8 16%
3–7 days
6 12%
1–4 weeks
21 43%
Over a month
10 20%

How the animals did

Recovered
15 18%
Still unwell when reported
6 7.2%
Died
2 2.4%
Euthanised
3 3.6%
Not known
57 69%

Problems reported at the same time

Age of the animals

Under 1 year
3
1–3 years
23
4–7 years
14
8–11 years
23
12+ years
15

About this medicine

Imidacloprid kills fleas (spot-on or collar).

Questions owners ask

Can Imidacloprid + Pyriproxyfen cause hair loss in cats?
83 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 14 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).

Hair loss with similar medicines

All reported side effects of Imidacloprid + Pyriproxyfen in cats · Medicines most reported with hair loss