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

29 reports to the FDA describe weight loss in dogs given Fipronil + S-methoprene. That is 1.0% of all reports for this medicine, compared with 1.7% across reports for all dog medicines, so it is reported less often than average with this medicine.

29Reports

79%Marked serious

28%Recovered

17%Died or euthanised

31 daysTypical onset

How soon it started

Same day

0 0.0%

1–2 days

2 15%

3–7 days

0 0.0%

1–4 weeks

4 31%

Over a month

7 54%

How the animals did

Recovered

8 28%

Still unwell when reported

10 34%

Died

4 14%

Euthanised

1 3.4%

Not known

6 21%

Problems reported at the same time

13 45%

13 45%

12 41%

7 24%

6 21%

5 17%

5 17%

5 17%

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 weight loss in dogs?: 29 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 31 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).

Weight loss with similar medicines

Weight loss after Spinosad (Comfortis) 531 reports · 0.9% of its reports
Weight loss after Lufenuron + Milbemycin Oxime (Sentinel) 280 reports · 1.1% of its reports
Weight loss after Imidacloprid + Moxidectin (Advantage Multi) 236 reports · 1.8% of its reports
Weight loss after Nitenpyram (Capstar) 89 reports · 0.8% of its reports
Weight loss after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 77 reports · 0.8% of its reports
Weight loss after Flumethrin + Imidacloprid (Seresto) 57 reports · 2.5% of its reports
Weight loss after Fipronil 28 reports · 2.0% of its reports

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