Breathing problems after Methimazole in cats

The FDA has received 90 reports of breathing problems in cats after Methimazole. That is 5.1% of all reports for this medicine, compared with 4.7% across reports for all cat medicines.

90Reports

74%Marked serious

27%Recovered

34%Died or euthanised

8 daysTypical onset

How soon it started

Same day

22 33%

1–2 days

10 15%

3–7 days

1 1.5%

1–4 weeks

15 23%

Over a month

18 27%

How the animals did

Recovered

22 24%

Recovered with lasting effects

2 2.2%

Still unwell when reported

20 22%

Died

17 19%

Euthanised

14 16%

Not known

15 17%

Problems reported at the same time

35 39%

30 33%

26 29%

26 29%

14 16%

Restlessness or agitation

14 16%

Liver problems

12 13%

Abnormal radiograph finding

12 13%

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 breathing problems in cats?: 90 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 8 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).

Breathing problems with similar medicines

Breathing problems after Velagliflozin (Senvelgo) 59 reports · 1.2% of its reports
Breathing problems after Bexagliflozin (Bexacat) 34 reports · 0.8% of its reports
Breathing problems after Insulin 76 reports · 2.0% of its reports

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