Hypokalaemia after Methimazole in cats

31 reports to the FDA describe hypokalaemia in cats given Methimazole. That is 1.7% 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.

31Reports

84%Marked serious

6.5%Recovered

26%Died or euthanised

29 daysTypical onset

How soon it started

Same day

2 8.3%

1–2 days

2 8.3%

3–7 days

1 4.2%

1–4 weeks

11 46%

Over a month

8 33%

How the animals did

Recovered

2 6.5%

Still unwell when reported

15 48%

Died

4 13%

Euthanised

4 13%

Not known

6 19%

Problems reported at the same time

22 71%

17 55%

16 52%

12 39%

12 39%

12 39%

11 35%

10 32%

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 hypokalaemia in cats?: 31 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 29 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).

Hypokalaemia with similar medicines

Hypokalaemia after Velagliflozin (Senvelgo) 235 reports · 4.9% of its reports
Hypokalaemia after Bexagliflozin (Bexacat) 160 reports · 3.9% of its reports
Hypokalaemia after Insulin 57 reports · 1.5% of its reports

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