Lethargy after Flumethrin + Imidacloprid (Seresto) in dogs

250 reports to the FDA describe lethargy in dogs given Flumethrin + Imidacloprid. That is 11% of all reports for this medicine, compared with 11% across reports for all dog medicines.

250Reports

50%Marked serious

36%Recovered

6.8%Died or euthanised

14 daysTypical onset

How soon it started

Same day

28 16%

1–2 days

27 15%

3–7 days

17 9.4%

1–4 weeks

46 26%

Over a month

62 34%

How the animals did

Recovered

89 36%

Recovered with lasting effects

1 0.4%

Still unwell when reported

48 19%

Died

10 4.0%

Euthanised

7 2.8%

Not known

95 38%

Problems reported at the same time

98 39%

88 35%

44 18%

43 17%

42 17%

28 11%

22 8.8%

21 8.4%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Imidacloprid kills fleas (spot-on or collar).

Products with this combination include Seresto. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Questions owners ask

Can Flumethrin + Imidacloprid cause lethargy in dogs?: 250 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).

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 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
Lethargy after Imidacloprid + Permethrin + Pyriproxyfen 106 reports · 14% of its reports

All reported side effects of Flumethrin + Imidacloprid in dogs · Medicines most reported with lethargy