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

23 reports to the FDA describe blood problems in dogs given Fipronil + S-methoprene. That is 0.8% of all reports for this medicine, compared with 1.8% across reports for all dog medicines, so it is reported less often than average with this medicine.

23Reports

83%Marked serious

8.7%Recovered

26%Died or euthanised

35 daysTypical onset

How soon it started

Same day

0 0.0%

1–2 days

3 30%

3–7 days

1 10%

1–4 weeks

1 10%

Over a month

5 50%

How the animals did

Recovered

2 8.7%

Still unwell when reported

4 17%

Died

3 13%

Euthanised

3 13%

Not known

11 48%

Problems reported at the same time

10 43%

9 39%

8 35%

8 35%

7 30%

7 30%

Pale mucous membrane

7 30%

Neutrophilia

7 30%

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 blood problems in dogs?: 23 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 35 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).

Blood problems with similar medicines

Blood problems after Spinosad (Comfortis) 364 reports · 0.6% of its reports
Blood problems after Lufenuron + Milbemycin Oxime (Sentinel) 184 reports · 0.7% of its reports
Blood problems after Imidacloprid + Moxidectin (Advantage Multi) 88 reports · 0.7% of its reports
Blood problems after Nitenpyram (Capstar) 54 reports · 0.5% of its reports
Blood problems after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 49 reports · 0.5% of its reports
Blood problems after Flumethrin + Imidacloprid (Seresto) 28 reports · 1.2% of its reports
Blood problems after Fipronil 20 reports · 1.4% of its reports
Blood problems after Lufenuron 27 reports · 2.7% of its reports

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