Behaviour change after Diphenhydramine in dogs

251 reports to the FDA describe behaviour change in dogs given Diphenhydramine. That is 5.3% of all reports for this medicine, compared with 2.5% across reports for all dog medicines, so it is reported unusually often with this medicine.

251Reports

55%Marked serious

31%Recovered

12%Died or euthanised

1 daysTypical onset

How soon it started

Same day

74 37%

1–2 days

40 20%

3–7 days

10 5.1%

1–4 weeks

23 12%

Over a month

51 26%

How the animals did

Recovered

71 28%

Recovered with lasting effects

7 2.8%

Still unwell when reported

90 36%

Died

12 4.8%

Euthanised

19 7.6%

Not known

52 21%

Problems reported at the same time

89 35%

88 35%

82 33%

62 25%

56 22%

51 20%

45 18%

41 16%

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 behaviour change in dogs?: 251 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).

Behaviour change with similar medicines

Behaviour change after Melarsomine (Immiticide) 278 reports · 1.2% of its reports
Behaviour change after Polysulfated Glycosaminoglycan 178 reports · 3.3% of its reports
Behaviour change after Butorphanol 151 reports · 3.4% of its reports
Behaviour change after Cefpodoxime 162 reports · 4.0% of its reports
Behaviour change after Tramadol 192 reports · 5.1% of its reports
Behaviour change after Florfenicol + Mometasone + Terbinafine 339 reports · 9.6% of its reports
Behaviour change after Desoxycorticosterone Pivalate 174 reports · 5.2% of its reports
Behaviour change after Propofol 71 reports · 2.3% of its reports
Behaviour change after Dirlotapide 107 reports · 3.8% of its reports
Behaviour change after Isoflurane 96 reports · 3.5% of its reports

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