Lethargy after Benadryl in dogs

The FDA has received 55 reports of lethargy in dogs after Benadryl. That is 23% of all reports for this medicine, compared with 11% across reports for all dog medicines, so it is reported unusually often with this medicine.

55Reports
82%Marked serious
13%Recovered
24%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
24 49%
1–2 days
7 14%
3–7 days
3 6.1%
1–4 weeks
8 16%
Over a month
7 14%

How the animals did

Recovered
7 13%
Still unwell when reported
30 55%
Died
4 7.3%
Euthanised
9 16%
Not known
5 9.1%

Problems reported at the same time

32 58%
20 36%
14 25%
13 24%
Fever
9 16%

Age of the animals

Under 1 year
5
1–3 years
13
4–7 years
13
8–11 years
16
12+ years
8

About this medicine

Type: medicine.

Questions owners ask

Can Benadryl cause lethargy in dogs?
55 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 1 day 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 Benadryl in dogs · Medicines most reported with lethargy