Inappropriate urination after Diphenhydramine in dogs

The FDA has received 70 reports of inappropriate urination in dogs after Diphenhydramine. That is 1.5% of all reports for this medicine, compared with 0.5% across reports for all dog medicines, so it is reported unusually often with this medicine.

70Reports

63%Marked serious

26%Recovered

13%Died or euthanised

2 daysTypical onset

How soon it started

Same day

28 45%

1–2 days

4 6.5%

3–7 days

6 9.7%

1–4 weeks

11 18%

Over a month

13 21%

How the animals did

Recovered

16 23%

Recovered with lasting effects

2 2.9%

Still unwell when reported

25 36%

Died

3 4.3%

Euthanised

6 8.6%

Not known

18 26%

Problems reported at the same time

23 33%

20 29%

19 27%

18 26%

17 24%

16 23%

Inappropriate defecation

14 20%

Allergic reaction

13 19%

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 inappropriate urination in dogs?: 70 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 2 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).

Inappropriate urination with similar medicines

Inappropriate urination after Melarsomine (Immiticide) 86 reports · 0.4% of its reports
Inappropriate urination after Polysulfated Glycosaminoglycan 49 reports · 0.9% of its reports
Inappropriate urination after Butorphanol 42 reports · 0.9% of its reports
Inappropriate urination after Cefpodoxime 56 reports · 1.4% of its reports
Inappropriate urination after Tramadol 79 reports · 2.1% of its reports
Inappropriate urination after Florfenicol + Mometasone + Terbinafine 49 reports · 1.4% of its reports
Inappropriate urination after Desoxycorticosterone Pivalate 74 reports · 2.2% of its reports
Inappropriate urination after Propofol 22 reports · 0.7% of its reports
Inappropriate urination after Isoflurane 28 reports · 1.0% of its reports
Inappropriate urination after Cephalexin 26 reports · 1.0% of its reports

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