Allergic reaction after Methimazole in cats

20 reports to the FDA describe allergic reaction in cats given Methimazole. That is 1.1% of all reports for this medicine, compared with 0.9% across reports for all cat medicines.

20Reports

75%Marked serious

40%Recovered

20%Died or euthanised

16 daysTypical onset

How soon it started

Same day

5 28%

1–2 days

0 0.0%

3–7 days

2 11%

1–4 weeks

8 44%

Over a month

3 17%

How the animals did

Recovered

7 35%

Recovered with lasting effects

1 5.0%

Still unwell when reported

4 20%

Died

2 10%

Euthanised

2 10%

Not known

4 20%

Problems reported at the same time

Vomiting

10 50%

Loss of appetite

6 30%

Breathing problems

5 25%

Uncoded sign

4 20%

4 20%

4 20%

3 15%

3 15%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Methimazole treats an overactive thyroid in cats.

Questions owners ask

Can Methimazole cause allergic reaction in cats?: 20 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 16 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).

All reported side effects of Methimazole in cats · Medicines most reported with allergic reaction