Lethargy after Fipronil + Pyriproxyfen + S-methoprene in dogs

The FDA has received 65 reports of lethargy in dogs after Fipronil + Pyriproxyfen + S-methoprene. That is 15% of all reports for this medicine, compared with 11% across reports for all dog medicines.

65Reports

45%Marked serious

49%Recovered

4.6%Died or euthanised

11 daysTypical onset

How soon it started

Same day

11 24%

1–2 days

9 20%

3–7 days

3 6.5%

1–4 weeks

12 26%

Over a month

11 24%

How the animals did

Recovered

32 49%

Still unwell when reported

2 3.1%

Died

1 1.5%

Euthanised

2 3.1%

Not known

28 43%

Problems reported at the same time

24 37%

23 35%

11 17%

10 15%

8 12%

Appetite loss

6 9.2%

Wobbliness (ataxia)

6 9.2%

Seizures

5 7.7%

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).

Questions owners ask

Can Fipronil + Pyriproxyfen + S-methoprene cause lethargy in dogs?: 65 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 11 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).

Lethargy with similar medicines

Lethargy after Spinosad (Comfortis) 7,303 reports · 13% of its reports
Lethargy after Lufenuron + Milbemycin Oxime (Sentinel) 2,341 reports · 9.0% of its reports
Lethargy after Imidacloprid + Moxidectin (Advantage Multi) 2,000 reports · 15% of its reports
Lethargy after Nitenpyram (Capstar) 1,204 reports · 11% of its reports
Lethargy after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 666 reports · 6.7% of its reports
Lethargy after Fipronil + S-methoprene (Frontline Plus) 447 reports · 15% of its reports
Lethargy after Flumethrin + Imidacloprid (Seresto) 250 reports · 11% of its reports
Lethargy after Imidacloprid 196 reports · 10% of its reports
Lethargy after Fipronil 185 reports · 13% of its reports
Lethargy after Lufenuron 205 reports · 20% of its reports

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