Lethargy after Cyphenothrin + Fipronil in dogs

The FDA has received 46 reports of lethargy in dogs after Cyphenothrin + Fipronil. That is 16% of all reports for this medicine, compared with 11% across reports for all dog medicines.

46Reports

63%Marked serious

57%Recovered

8.7%Died or euthanised

1 daysTypical onset

How soon it started

Same day

12 43%

1–2 days

4 14%

3–7 days

1 3.6%

1–4 weeks

3 11%

Over a month

8 29%

How the animals did

Recovered

26 57%

Still unwell when reported

11 24%

Died

2 4.3%

Euthanised

2 4.3%

Not known

5 11%

Problems reported at the same time

16 35%

13 28%

12 26%

11 24%

Restlessness or agitation

7 15%

Vocalising

6 13%

Diarrhea

5 11%

Anxiety

4 8.7%

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 Cyphenothrin + Fipronil cause lethargy in dogs?: 46 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 1 day 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).

Lethargy with similar medicines

Lethargy after Spinosad (Comfortis) 7,303 reports · 13% of its reports
Lethargy after Lufenuron + Milbemycin Oxime (Sentinel) 2,341 reports · 9.0% of its reports
Lethargy after Imidacloprid + Moxidectin (Advantage Multi) 2,000 reports · 15% of its reports
Lethargy after Nitenpyram (Capstar) 1,204 reports · 11% of its reports
Lethargy after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 666 reports · 6.7% of its reports
Lethargy after Fipronil + S-methoprene (Frontline Plus) 447 reports · 15% of its reports
Lethargy after Flumethrin + Imidacloprid (Seresto) 250 reports · 11% of its reports
Lethargy after Imidacloprid 196 reports · 10% of its reports
Lethargy after Fipronil 185 reports · 13% of its reports
Lethargy after Lufenuron 205 reports · 20% of its reports

All reported side effects of Cyphenothrin + Fipronil in dogs · Medicines most reported with lethargy