Diarrhea after Methimazole in cats

The FDA has received 111 reports of diarrhea in cats after Methimazole. That is 6.2% of all reports for this medicine, compared with 5.1% across reports for all cat medicines.

111Reports

52%Marked serious

16%Recovered

14%Died or euthanised

6 daysTypical onset

How soon it started

Same day

19 22%

1–2 days

14 16%

3–7 days

13 15%

1–4 weeks

15 17%

Over a month

26 30%

How the animals did

Recovered

17 15%

Recovered with lasting effects

1 0.9%

Still unwell when reported

47 42%

Died

8 7.2%

Euthanised

8 7.2%

Not known

30 27%

Problems reported at the same time

49 44%

45 41%

31 28%

26 23%

17 15%

15 14%

12 11%

11 9.9%

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 diarrhea in cats?: 111 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 6 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).

Diarrhea with similar medicines

Diarrhea after Velagliflozin (Senvelgo) 766 reports · 16% of its reports
Diarrhea after Bexagliflozin (Bexacat) 775 reports · 19% of its reports
Diarrhea after Insulin 197 reports · 5.3% of its reports

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