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

The FDA has received 68 reports of liver problems in dogs after Fipronil + S-methoprene. That is 2.3% of all reports for this medicine, compared with 4.6% across reports for all dog medicines, so it is reported less often than average with this medicine.

68Reports

66%Marked serious

19%Recovered

18%Died or euthanised

29 daysTypical onset

How soon it started

Same day

4 11%

1–2 days

4 11%

3–7 days

2 5.6%

1–4 weeks

9 25%

Over a month

17 47%

How the animals did

Recovered

12 18%

Recovered with lasting effects

1 1.5%

Still unwell when reported

18 26%

Died

3 4.4%

Euthanised

9 13%

Not known

25 37%

Problems reported at the same time

27 40%

24 35%

22 32%

15 22%

12 18%

12 18%

12 18%

11 16%

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 liver problems in dogs?: 68 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 29 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).

Liver problems with similar medicines

Liver problems after Spinosad (Comfortis) 955 reports · 1.7% of its reports
Liver problems after Lufenuron + Milbemycin Oxime (Sentinel) 414 reports · 1.6% of its reports
Liver problems after Imidacloprid + Moxidectin (Advantage Multi) 197 reports · 1.5% of its reports
Liver problems after Nitenpyram (Capstar) 87 reports · 0.8% of its reports
Liver problems after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 132 reports · 1.3% of its reports
Liver problems after Flumethrin + Imidacloprid (Seresto) 47 reports · 2.1% of its reports
Liver problems after Fipronil 53 reports · 3.8% of its reports
Liver problems after Lufenuron 53 reports · 5.2% of its reports
Liver problems after Imidacloprid + Permethrin + Pyriproxyfen 21 reports · 2.8% of its reports
Liver problems after Imidacloprid + Permethrin 24 reports · 5.1% of its reports

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