Lymphopenia after Ilunocitinib (Zenrelia) in dogs

The FDA has received 149 reports of lymphopenia in dogs after Ilunocitinib. That is 6.8% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported unusually often with this medicine.

149Reports

39%Marked serious

15%Recovered

11%Died or euthanised

95 daysTypical onset

How soon it started

Same day

6 4.9%

1–2 days

3 2.5%

3–7 days

2 1.6%

1–4 weeks

21 17%

Over a month

90 74%

How the animals did

Recovered

22 15%

Still unwell when reported

54 36%

Died

5 3.4%

Euthanised

12 8.1%

Not known

56 38%

Problems reported at the same time

66 44%

62 42%

55 37%

48 32%

47 32%

Decreased haematocrit

47 32%

Leukopenia

47 32%

Loss of appetite

40 27%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Ilunocitinib controls itching from allergies (tablet, a JAK inhibitor).

Products with this ingredient include Zenrelia. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Questions owners ask

Can Ilunocitinib cause lymphopenia in dogs?: 149 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 95 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).

Lymphopenia with similar medicines

Lymphopenia after Oclacitinib (Apoquel) 439 reports · 1.5% of its reports
Lymphopenia after Cyclosporine (Atopica) 83 reports · 0.5% of its reports

All reported side effects of Ilunocitinib in dogs · Medicines most reported with lymphopenia