Seizures after Methimazole in cats

64 reports to the FDA describe seizures in cats given Methimazole. That is 3.6% of all reports for this medicine, compared with 2.6% across reports for all cat medicines.

64Reports

89%Marked serious

22%Recovered

23%Died or euthanised

8 daysTypical onset

How soon it started

Same day

6 12%

1–2 days

10 20%

3–7 days

7 14%

1–4 weeks

12 24%

Over a month

16 31%

How the animals did

Recovered

14 22%

Still unwell when reported

20 31%

Died

7 11%

Euthanised

8 13%

Not known

15 23%

Problems reported at the same time

15 23%

13 20%

10 16%

9 14%

7 11%

7 11%

7 11%

6 9.4%

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 seizures in cats?: 64 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).

Seizures with similar medicines

Seizures after Bexagliflozin (Bexacat) 20 reports · 0.5% of its reports
Seizures after Insulin 182 reports · 4.9% of its reports

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