Dehydration after Diphenhydramine in dogs

The FDA has received 104 reports of dehydration in dogs after Diphenhydramine. That is 2.2% of all reports for this medicine, compared with 0.7% across reports for all dog medicines, so it is reported unusually often with this medicine.

104Reports
71%Marked serious
13%Recovered
33%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
40 46%
1–2 days
14 16%
3–7 days
10 11%
1–4 weeks
12 14%
Over a month
11 13%

How the animals did

Recovered
13 13%
Still unwell when reported
38 37%
Died
14 13%
Euthanised
20 19%
Not known
19 18%

Problems reported at the same time

Age of the animals

Under 1 year
11
1–3 years
30
4–7 years
29
8–11 years
22
12+ years
11

About this medicine

Type: medicine.

Questions owners ask

Can Diphenhydramine cause dehydration in dogs?
104 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).

Dehydration with similar medicines

All reported side effects of Diphenhydramine in dogs · Medicines most reported with dehydration