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

The FDA has received 34 reports of disorientation in dogs after Fipronil + S-methoprene. That is 1.2% of all reports for this medicine, compared with 1.0% across reports for all dog medicines.

34Reports

82%Marked serious

50%Recovered

2.9%Died or euthanised

19 daysTypical onset

How soon it started

Same day

2 11%

1–2 days

6 33%

3–7 days

1 5.6%

1–4 weeks

1 5.6%

Over a month

8 44%

How the animals did

Recovered

17 50%

Still unwell when reported

3 8.8%

Died

1 2.9%

Not known

13 38%

Problems reported at the same time

14 41%

12 35%

7 21%

5 15%

5 15%

5 15%

Musculoskeletal disorder

4 12%

Circling - neurological disorder

4 12%

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 disorientation in dogs?: 34 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 19 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).

Disorientation with similar medicines

Disorientation after Spinosad (Comfortis) 497 reports · 0.9% of its reports
Disorientation after Lufenuron + Milbemycin Oxime (Sentinel) 154 reports · 0.6% of its reports
Disorientation after Imidacloprid + Moxidectin (Advantage Multi) 182 reports · 1.4% of its reports
Disorientation after Nitenpyram (Capstar) 183 reports · 1.7% of its reports
Disorientation after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 67 reports · 0.7% of its reports
Disorientation after Imidacloprid 23 reports · 1.2% of its reports
Disorientation after Fipronil 24 reports · 1.7% of its reports

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