Didn't work as expected after Diphenhydramine in dogs

The FDA has received 585 reports of didn't work as expected in dogs after Diphenhydramine. That is 12% of all reports for this medicine, compared with 13% across reports for all dog medicines.

585Reports

31%Marked serious

14%Recovered

4.4%Died or euthanised

9 daysTypical onset

How soon it started

Same day

116 28%

1–2 days

47 11%

3–7 days

40 9.5%

1–4 weeks

78 19%

Over a month

139 33%

How the animals did

Recovered

73 12%

Recovered with lasting effects

8 1.4%

Still unwell when reported

222 38%

Died

8 1.4%

Euthanised

18 3.1%

Not known

256 44%

Problems reported at the same time

Injection site reaction

138 24%

134 23%

121 21%

85 15%

79 14%

77 13%

50 8.5%

49 8.4%

Age of the animals

Under 1 year

1–3 years

117

4–7 years

188

8–11 years

158

12+ years

About this medicine

Type: medicine.

Questions owners ask

Can Diphenhydramine cause didn't work as expected in dogs?: 585 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 9 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).

Didn't work as expected with similar medicines

Didn't work as expected after Melarsomine (Immiticide) 646 reports · 2.8% of its reports
Didn't work as expected after Polysulfated Glycosaminoglycan 698 reports · 13% of its reports
Didn't work as expected after Butorphanol 1,022 reports · 23% of its reports
Didn't work as expected after Cefpodoxime 671 reports · 17% of its reports
Didn't work as expected after Tramadol 475 reports · 13% of its reports
Didn't work as expected after Florfenicol + Mometasone + Terbinafine 969 reports · 27% of its reports
Didn't work as expected after Desoxycorticosterone Pivalate 355 reports · 11% of its reports
Didn't work as expected after Propofol 600 reports · 20% of its reports
Didn't work as expected after Dirlotapide 712 reports · 25% of its reports
Didn't work as expected after Isoflurane 474 reports · 17% of its reports

All reported side effects of Diphenhydramine in dogs · Medicines most reported with didn't work as expected