Vomiting after Fipronil + S-methoprene (Frontline Plus) in cats

The FDA has received 54 reports of vomiting in cats after Fipronil + S-methoprene. That is 15% of all reports for this medicine, compared with 18% across reports for all cat medicines.

54Reports

20%Marked serious

63%Recovered

3.7%Died or euthanised

18 daysTypical onset

How soon it started

Same day

12 26%

1–2 days

3 6.5%

3–7 days

3 6.5%

1–4 weeks

12 26%

Over a month

16 35%

How the animals did

Recovered

32 59%

Recovered with lasting effects

2 3.7%

Still unwell when reported

7 13%

Died

2 3.7%

Not known

11 20%

Problems reported at the same time

Lethargy

19 35%

Loss of appetite

9 17%

Diarrhea

9 17%

Unpalatable

3 5.6%

Didn't stop fleas

3 5.6%

Drooling

3 5.6%

Vocalising

3 5.6%

Weight loss

3 5.6%

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 vomiting in cats?: 54 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 18 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).

Vomiting with similar medicines

Vomiting after Spinosad (Comfortis) 8,410 reports · 73% of its reports
Vomiting after Nitenpyram (Capstar) 630 reports · 7.2% of its reports
Vomiting after Imidacloprid + Moxidectin (Advantage Multi) 861 reports · 11% of its reports
Vomiting after Lufenuron 222 reports · 20% of its reports
Vomiting after Flumethrin + Imidacloprid (Seresto) 59 reports · 8.8% of its reports
Vomiting after Imidacloprid + Pyriproxyfen 68 reports · 10% of its reports
Vomiting after Fipronil 82 reports · 16% of its reports
Vomiting after Imidacloprid 37 reports · 15% of its reports

All reported side effects of Fipronil + S-methoprene in cats · Medicines most reported with vomiting