Lethargy after Frontline Plus in dogs

The FDA has received 24 reports of lethargy in dogs after Frontline Plus. That is 40% of all reports for this medicine, compared with 11% across reports for all dog medicines, so it is reported unusually often with this medicine.

24Reports
42%Marked serious
46%Recovered
8.3%Died or euthanised
91 daysTypical onset
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How soon it started

Same day
1 7.1%
1–2 days
1 7.1%
3–7 days
1 7.1%
1–4 weeks
1 7.1%
Over a month
10 71%

How the animals did

Recovered
11 46%
Died
1 4.2%
Euthanised
1 4.2%
Not known
11 46%

Problems reported at the same time

Loss of appetite
8 33%
Vomiting
7 29%
Breathing problems
4 17%
Not drinking
3 13%
Behaviour change
3 13%
Tremors
2 8.3%
Death
2 8.3%
Tachycardia
2 8.3%

Age of the animals

Under 1 year
5
1–3 years
8
4–7 years
7
8–11 years
3
12+ years
0

About this medicine

Type: medicine.

Questions owners ask

Can Frontline Plus cause lethargy 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 91 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

All reported side effects of Frontline Plus in dogs · Medicines most reported with lethargy