Prolonged activated partial thrombin time (aptt) after Diphenhydramine in dogs

26 reports to the FDA describe prolonged activated partial thrombin time (aptt) in dogs given Diphenhydramine. That is 0.6% of all reports for this medicine, compared with 0.0% across reports for all dog medicines, so it is reported unusually often with this medicine.

26Reports

96%Marked serious

3.8%Recovered

50%Died or euthanised

Same dayTypical onset

How soon it started

Same day

14 64%

1–2 days

1 4.5%

3–7 days

2 9.1%

1–4 weeks

1 4.5%

Over a month

4 18%

How the animals did

Recovered

1 3.8%

Still unwell when reported

12 46%

Died

4 15%

Euthanised

9 35%

Problems reported at the same time

17 65%

16 62%

14 54%

13 50%

13 50%

13 50%

12 46%

11 42%

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 prolonged activated partial thrombin time (aptt) in dogs?: 26 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 the same 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).

Prolonged activated partial thrombin time (aptt) with similar medicines

Prolonged activated partial thrombin time (aptt) after Melarsomine (Immiticide) 21 reports · 0.1% of its reports
Prolonged activated partial thrombin time (aptt) after Polysulfated Glycosaminoglycan 27 reports · 0.5% of its reports

All reported side effects of Diphenhydramine in dogs · Medicines most reported with prolonged activated partial thrombin time (aptt)