Involuntary defecation after Diphenhydramine in dogs

The FDA has received 30 reports of involuntary defecation in dogs after Diphenhydramine. That is 0.6% of all reports for this medicine, compared with 0.1% across reports for all dog medicines, so it is reported unusually often with this medicine.

30Reports

90%Marked serious

37%Recovered

13%Died or euthanised

Same dayTypical onset

How soon it started

Same day

23 79%

1–2 days

2 6.9%

3–7 days

1 3.4%

1–4 weeks

1 3.4%

Over a month

2 6.9%

How the animals did

Recovered

11 37%

Still unwell when reported

11 37%

Died

2 6.7%

Euthanised

2 6.7%

Not known

4 13%

Problems reported at the same time

22 73%

16 53%

14 47%

10 33%

9 30%

8 27%

6 20%

5 17%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Type: medicine.

Questions owners ask

Can Diphenhydramine cause involuntary defecation in dogs?: 30 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 the same 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).

Involuntary defecation with similar medicines

Involuntary defecation after Melarsomine (Immiticide) 68 reports · 0.3% of its reports

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