Itching after Fipronil + S-methoprene (Frontline Plus) in dogs

330 reports to the FDA describe itching in dogs given Fipronil + S-methoprene. That is 11% of all reports for this medicine, compared with 4.3% across reports for all dog medicines, so it is reported unusually often with this medicine.

330Reports

52%Marked serious

29%Recovered

1.5%Died or euthanised

24 daysTypical onset

How soon it started

Same day

31 16%

1–2 days

18 9.2%

3–7 days

24 12%

1–4 weeks

42 21%

Over a month

81 41%

How the animals did

Recovered

91 28%

Recovered with lasting effects

4 1.2%

Still unwell when reported

33 10%

Died

1 0.3%

Euthanised

4 1.2%

Not known

197 60%

Problems reported at the same time

59 18%

36 11%

35 11%

31 9.4%

Application site reaction

27 8.2%

Restlessness or agitation

25 7.6%

Skin disorders

22 6.7%

Skin rash or irritation

20 6.1%

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).

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

Questions owners ask

Can Fipronil + S-methoprene cause itching in dogs?: 330 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 24 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).

Itching with similar medicines

Itching after Spinosad (Comfortis) 3,874 reports · 6.8% of its reports
Itching after Lufenuron + Milbemycin Oxime (Sentinel) 1,223 reports · 4.7% of its reports
Itching after Imidacloprid + Moxidectin (Advantage Multi) 2,227 reports · 17% of its reports
Itching after Nitenpyram (Capstar) 1,450 reports · 13% of its reports
Itching after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 281 reports · 2.8% of its reports
Itching after Flumethrin + Imidacloprid (Seresto) 610 reports · 27% of its reports
Itching after Imidacloprid 297 reports · 16% of its reports
Itching after Fipronil 138 reports · 9.8% of its reports
Itching after Lufenuron 178 reports · 17% of its reports
Itching after Imidacloprid + Permethrin + Pyriproxyfen 206 reports · 28% of its reports

All reported side effects of Fipronil + S-methoprene in dogs · Medicines most reported with itching