Low platelet count after Diphenhydramine in dogs

50 reports to the FDA describe low platelet count in dogs given 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.

50Reports

90%Marked serious

0.0%Recovered

36%Died or euthanised

1 daysTypical onset

How soon it started

Same day

15 41%

1–2 days

6 16%

3–7 days

4 11%

1–4 weeks

3 8.1%

Over a month

9 24%

How the animals did

Still unwell when reported

28 56%

Died

6 12%

Euthanised

12 24%

Not known

4 8.0%

Problems reported at the same time

28 56%

27 54%

25 50%

23 46%

20 40%

18 36%

16 32%

15 30%

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 low platelet count in dogs?: 50 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).

Low platelet count with similar medicines

Low platelet count after Melarsomine (Immiticide) 58 reports · 0.3% of its reports
Low platelet count after Polysulfated Glycosaminoglycan 70 reports · 1.3% of its reports
Low platelet count after Butorphanol 28 reports · 0.6% of its reports
Low platelet count after Cefpodoxime 43 reports · 1.1% of its reports
Low platelet count after Tramadol 45 reports · 1.2% of its reports
Low platelet count after Propofol 24 reports · 0.8% of its reports
Low platelet count after Isoflurane 28 reports · 1.0% of its reports
Low platelet count after Cephalexin 21 reports · 0.8% of its reports
Low platelet count after Famotidine 54 reports · 2.0% of its reports
Low platelet count after Chondroitin + Glucosamine 23 reports · 0.9% of its reports

All reported side effects of Diphenhydramine in dogs · Medicines most reported with low platelet count