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

The FDA has received 42 reports of swelling in dogs after Fipronil + S-methoprene. That is 1.4% of all reports for this medicine, compared with 2.8% across reports for all dog medicines, so it is reported less often than average with this medicine.

42Reports

67%Marked serious

38%Recovered

4.8%Died or euthanised

23 daysTypical onset

How soon it started

Same day

3 13%

1–2 days

3 13%

3–7 days

2 8.3%

1–4 weeks

6 25%

Over a month

10 42%

How the animals did

Recovered

15 36%

Recovered with lasting effects

1 2.4%

Still unwell when reported

5 12%

Euthanised

2 4.8%

Not known

19 45%

Problems reported at the same time

Vomiting

11 26%

Lethargy

9 21%

Itching

7 17%

Application site reaction

6 14%

6 14%

5 12%

5 12%

4 9.5%

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 swelling in dogs?: 42 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 23 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).

Swelling with similar medicines

Swelling after Spinosad (Comfortis) 399 reports · 0.7% of its reports
Swelling after Lufenuron + Milbemycin Oxime (Sentinel) 219 reports · 0.8% of its reports
Swelling after Imidacloprid + Moxidectin (Advantage Multi) 218 reports · 1.7% of its reports
Swelling after Nitenpyram (Capstar) 127 reports · 1.2% of its reports
Swelling after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 70 reports · 0.7% of its reports
Swelling after Flumethrin + Imidacloprid (Seresto) 47 reports · 2.1% of its reports
Swelling after Fipronil 20 reports · 1.4% of its reports
Swelling after Lufenuron 44 reports · 4.3% of its reports

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