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

The FDA has received 24 reports of inappropriate urination in dogs after Fipronil + S-methoprene. That is 0.8% of all reports for this medicine, compared with 0.5% across reports for all dog medicines, so it is reported unusually often with this medicine.

24Reports

58%Marked serious

42%Recovered

0.0%Died or euthanised

33 daysTypical onset

How soon it started

Same day

2 13%

1–2 days

0 0.0%

3–7 days

0 0.0%

1–4 weeks

5 33%

Over a month

8 53%

How the animals did

Recovered

9 38%

Recovered with lasting effects

1 4.2%

Still unwell when reported

3 13%

Not known

11 46%

Problems reported at the same time

8 33%

8 33%

6 25%

6 25%

5 21%

4 17%

3 13%

3 13%

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 inappropriate urination in dogs?: 24 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 33 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).

Inappropriate urination with similar medicines

Inappropriate urination after Spinosad (Comfortis) 140 reports · 0.2% of its reports
Inappropriate urination after Lufenuron + Milbemycin Oxime (Sentinel) 59 reports · 0.2% of its reports
Inappropriate urination after Imidacloprid + Moxidectin (Advantage Multi) 76 reports · 0.6% of its reports
Inappropriate urination after Nitenpyram (Capstar) 28 reports · 0.3% of its reports
Inappropriate urination after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 27 reports · 0.3% of its reports

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