Death after Methimazole in cats

The FDA has received 211 reports of death in cats after Methimazole. That is 12% of all reports for this medicine, compared with 8.9% across reports for all cat medicines.

211Reports

91%Marked serious

0.5%Recovered

100%Died or euthanised

20 daysTypical onset

How soon it started

Same day

32 20%

1–2 days

13 8.2%

3–7 days

12 7.5%

1–4 weeks

41 26%

Over a month

61 38%

How the animals did

Recovered

1 0.5%

Died

97 46%

Euthanised

113 54%

Problems reported at the same time

88 42%

64 30%

43 20%

41 19%

38 18%

33 16%

30 14%

28 13%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

157

About this medicine

Methimazole treats an overactive thyroid in cats.

Questions owners ask

Can Methimazole cause death in cats?: 211 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 20 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).

Death with similar medicines

Death after Velagliflozin (Senvelgo) 380 reports · 7.9% of its reports
Death after Bexagliflozin (Bexacat) 319 reports · 7.9% of its reports
Death after Insulin 456 reports · 12% of its reports

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