Bradycardia after Amitraz + Fipronil + S-methoprene in dogs

The FDA has received 20 reports of bradycardia in dogs after Amitraz + Fipronil + S-methoprene. That is 4.3% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported unusually often with this medicine.

20Reports

95%Marked serious

30%Recovered

0.0%Died or euthanised

17 daysTypical onset

How soon it started

Same day

6 33%

1–2 days

2 11%

3–7 days

1 5.6%

1–4 weeks

1 5.6%

Over a month

8 44%

How the animals did

Recovered

6 30%

Not known

14 70%

Problems reported at the same time

Lethargy

17 85%

Wobbliness (ataxia)

6 30%

Vomiting

3 15%

Vocalising

2 10%

Loss of appetite

2 10%

Walking difficulty

2 10%

Decreased heart rate

1 5.0%

Restlessness or agitation

1 5.0%

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 bradycardia in dogs?: 20 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 17 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).

Bradycardia with similar medicines

Bradycardia after Spinosad (Comfortis) 64 reports · 0.1% of its reports
Bradycardia after Lufenuron + Milbemycin Oxime (Sentinel) 26 reports · 0.1% of its reports

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