Abnormal cytology after Diphenhydramine in dogs

The FDA has received 52 reports of abnormal cytology in dogs after Diphenhydramine. That is 1.1% of all reports for this medicine, compared with 0.2% across reports for all dog medicines, so it is reported unusually often with this medicine.

52Reports

62%Marked serious

3.8%Recovered

15%Died or euthanised

2 daysTypical onset

How soon it started

Same day

9 21%

1–2 days

13 30%

3–7 days

5 12%

1–4 weeks

3 7.0%

Over a month

13 30%

How the animals did

Recovered

2 3.8%

Still unwell when reported

30 58%

Died

1 1.9%

Euthanised

7 13%

Not known

12 23%

Problems reported at the same time

Swelling

25 48%

Loss of appetite

17 33%

Didn't work as expected

16 31%

Injection site reaction

16 31%

15 29%

15 29%

11 21%

10 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 abnormal cytology in dogs?: 52 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).

Abnormal cytology with similar medicines

Abnormal cytology after Melarsomine (Immiticide) 126 reports · 0.6% of its reports
Abnormal cytology after Polysulfated Glycosaminoglycan 21 reports · 0.4% of its reports
Abnormal cytology after Butorphanol 43 reports · 1.0% of its reports
Abnormal cytology after Cefpodoxime 96 reports · 2.4% of its reports
Abnormal cytology after Tramadol 43 reports · 1.1% of its reports
Abnormal cytology after Florfenicol + Mometasone + Terbinafine 88 reports · 2.5% of its reports
Abnormal cytology after Propofol 20 reports · 0.7% of its reports
Abnormal cytology after Isoflurane 31 reports · 1.1% of its reports
Abnormal cytology after Cephalexin 45 reports · 1.7% of its reports
Abnormal cytology after Famotidine 39 reports · 1.5% of its reports

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