Hair loss after Amitraz + Fipronil + S-methoprene in dogs

The FDA has received 40 reports of hair loss in dogs after Amitraz + Fipronil + S-methoprene. That is 8.7% of all reports for this medicine, compared with 1.0% across reports for all dog medicines, so it is reported unusually often with this medicine.

40Reports

85%Marked serious

28%Recovered

2.5%Died or euthanised

48 daysTypical onset

How soon it started

Same day

2 7.4%

1–2 days

2 7.4%

3–7 days

0 0.0%

1–4 weeks

5 19%

Over a month

18 67%

How the animals did

Recovered

10 25%

Recovered with lasting effects

1 2.5%

Still unwell when reported

3 7.5%

Euthanised

1 2.5%

Not known

25 63%

Problems reported at the same time

Application site reaction

23 57%

Lethargy

15 38%

Itching

11 28%

Skin redness

10 25%

Skin rash or irritation

9 23%

Pemphigus foliaceus

4 10%

Vomiting

4 10%

Pr-skin, lesion(s)

3 7.5%

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).

Questions owners ask

Can Amitraz + Fipronil + S-methoprene cause hair loss in dogs?: 40 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 48 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).

Hair loss with similar medicines

Hair loss after Spinosad (Comfortis) 503 reports · 0.9% of its reports
Hair loss after Lufenuron + Milbemycin Oxime (Sentinel) 227 reports · 0.9% of its reports
Hair loss after Imidacloprid + Moxidectin (Advantage Multi) 452 reports · 3.4% of its reports
Hair loss after Nitenpyram (Capstar) 195 reports · 1.8% of its reports
Hair loss after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 46 reports · 0.5% of its reports
Hair loss after Fipronil + S-methoprene (Frontline Plus) 113 reports · 3.8% of its reports
Hair loss after Flumethrin + Imidacloprid (Seresto) 135 reports · 5.9% of its reports
Hair loss after Imidacloprid 43 reports · 2.3% of its reports
Hair loss after Fipronil 22 reports · 1.6% of its reports
Hair loss after Lufenuron 45 reports · 4.4% of its reports

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