Behaviour change after Fipronil in dogs

The FDA has received 66 reports of behaviour change in dogs after Fipronil. That is 4.7% of all reports for this medicine, compared with 2.5% across reports for all dog medicines, so it is reported unusually often with this medicine.

66Reports

42%Marked serious

45%Recovered

7.6%Died or euthanised

37 daysTypical onset

How soon it started

Same day

7 16%

1–2 days

2 4.4%

3–7 days

2 4.4%

1–4 weeks

7 16%

Over a month

27 60%

How the animals did

Recovered

26 39%

Recovered with lasting effects

4 6.1%

Still unwell when reported

12 18%

Died

1 1.5%

Euthanised

4 6.1%

Not known

19 29%

Problems reported at the same time

19 29%

17 26%

12 18%

12 18%

10 15%

Restlessness or agitation

9 14%

Breathing problems

8 12%

Disorientation

7 11%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Fipronil kills fleas and ticks (spot-on).

Questions owners ask

Can Fipronil cause behaviour change in dogs?: 66 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 37 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).

Behaviour change with similar medicines

Behaviour change after Spinosad (Comfortis) 1,176 reports · 2.1% of its reports
Behaviour change after Lufenuron + Milbemycin Oxime (Sentinel) 358 reports · 1.4% of its reports
Behaviour change after Imidacloprid + Moxidectin (Advantage Multi) 1,205 reports · 9.2% of its reports
Behaviour change after Nitenpyram (Capstar) 323 reports · 3.0% of its reports
Behaviour change after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 128 reports · 1.3% of its reports
Behaviour change after Fipronil + S-methoprene (Frontline Plus) 181 reports · 6.1% of its reports
Behaviour change after Flumethrin + Imidacloprid (Seresto) 167 reports · 7.3% of its reports
Behaviour change after Imidacloprid 94 reports · 4.9% of its reports
Behaviour change after Lufenuron 20 reports · 2.0% of its reports
Behaviour change after Imidacloprid + Permethrin + Pyriproxyfen 70 reports · 9.5% of its reports

All reported side effects of Fipronil in dogs · Medicines most reported with behaviour change