Liver problems after Methimazole in cats

148 reports to the FDA describe liver problems in cats given Methimazole. That is 8.3% of all reports for this medicine, compared with 2.8% across reports for all cat medicines, so it is reported unusually often with this medicine.

148Reports

61%Marked serious

8.8%Recovered

26%Died or euthanised

27 daysTypical onset

How soon it started

Same day

9 7.3%

1–2 days

6 4.9%

3–7 days

6 4.9%

1–4 weeks

58 47%

Over a month

44 36%

How the animals did

Recovered

12 8.1%

Recovered with lasting effects

1 0.7%

Still unwell when reported

33 22%

Died

16 11%

Euthanised

23 16%

Not known

63 43%

Problems reported at the same time

77 52%

47 32%

47 32%

40 27%

38 26%

37 25%

25 17%

21 14%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

108

About this medicine

Methimazole treats an overactive thyroid in cats.

Questions owners ask

Can Methimazole cause liver problems in cats?: 148 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 27 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).

Liver problems with similar medicines

Liver problems after Velagliflozin (Senvelgo) 339 reports · 7.1% of its reports
Liver problems after Bexagliflozin (Bexacat) 309 reports · 7.6% of its reports
Liver problems after Insulin 155 reports · 4.1% of its reports

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