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

The FDA has received 230 reports of diarrhea in dogs after Fipronil + S-methoprene. That is 7.8% of all reports for this medicine, compared with 8.4% across reports for all dog medicines.

230Reports

58%Marked serious

40%Recovered

5.2%Died or euthanised

22 daysTypical onset

How soon it started

Same day

24 19%

1–2 days

15 12%

3–7 days

12 9.6%

1–4 weeks

21 17%

Over a month

53 42%

How the animals did

Recovered

89 39%

Recovered with lasting effects

2 0.9%

Still unwell when reported

25 11%

Died

3 1.3%

Euthanised

9 3.9%

Not known

102 44%

Problems reported at the same time

109 47%

54 23%

54 23%

15 6.5%

13 5.7%

12 5.2%

12 5.2%

11 4.8%

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 diarrhea in dogs?: 230 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 22 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).

Diarrhea with similar medicines

Diarrhea after Spinosad (Comfortis) 2,388 reports · 4.2% of its reports
Diarrhea after Lufenuron + Milbemycin Oxime (Sentinel) 2,524 reports · 9.7% of its reports
Diarrhea after Imidacloprid + Moxidectin (Advantage Multi) 1,203 reports · 9.2% of its reports
Diarrhea after Nitenpyram (Capstar) 626 reports · 5.8% of its reports
Diarrhea after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 800 reports · 8.0% of its reports
Diarrhea after Flumethrin + Imidacloprid (Seresto) 130 reports · 5.7% of its reports
Diarrhea after Imidacloprid 93 reports · 4.9% of its reports
Diarrhea after Fipronil 123 reports · 8.7% of its reports
Diarrhea after Lufenuron 182 reports · 18% of its reports
Diarrhea after Imidacloprid + Permethrin + Pyriproxyfen 53 reports · 7.2% of its reports

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