Abnormal ultrasound finding after Methimazole in cats

22 reports to the FDA describe abnormal ultrasound finding in cats given Methimazole. That is 1.2% of all reports for this medicine, compared with 0.5% across reports for all cat medicines, so it is reported unusually often with this medicine.

22Reports

91%Marked serious

0.0%Recovered

27%Died or euthanised

18 daysTypical onset

How soon it started

Same day

2 14%

1–2 days

2 14%

3–7 days

0 0.0%

1–4 weeks

6 43%

Over a month

4 29%

How the animals did

Still unwell when reported

8 36%

Died

2 9.1%

Euthanised

4 18%

Not known

8 36%

Problems reported at the same time

9 41%

9 41%

8 36%

8 36%

8 36%

7 32%

6 27%

5 23%

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 abnormal ultrasound finding in cats?: 22 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 18 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).

Abnormal ultrasound finding with similar medicines

Abnormal ultrasound finding after Velagliflozin (Senvelgo) 92 reports · 1.9% of its reports
Abnormal ultrasound finding after Bexagliflozin (Bexacat) 70 reports · 1.7% of its reports
Abnormal ultrasound finding after Insulin 40 reports · 1.1% of its reports

All reported side effects of Methimazole in cats · Medicines most reported with abnormal ultrasound finding