Lethargy after Heartgard in dogs

The FDA has received 26 reports of lethargy in dogs after Heartgard. That is 6.9% of all reports for this medicine, compared with 11% across reports for all dog medicines, so it is reported less often than average with this medicine.

26Reports
65%Marked serious
19%Recovered
7.7%Died or euthanised
35 daysTypical onset
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How soon it started

Same day
4 25%
1–2 days
1 6.3%
3–7 days
1 6.3%
1–4 weeks
2 13%
Over a month
8 50%

How the animals did

Recovered
5 19%
Still unwell when reported
15 58%
Euthanised
2 7.7%
Not known
4 15%

Problems reported at the same time

Breathing problems
6 23%
Weight loss
6 23%
Tremors
3 12%
Lameness
3 12%

Age of the animals

Under 1 year
2
1–3 years
6
4–7 years
9
8–11 years
7
12+ years
1

About this medicine

Type: medicine.

Questions owners ask

Can Heartgard cause lethargy in dogs?
26 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 35 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 Heartgard in dogs · Medicines most reported with lethargy