Methimazole side effects in cats
1,781 reports sent to the FDA between 1998 and 2026 involve Methimazole in cats. The most reported problems were loss of appetite, vomiting, lethargy. 46% were marked serious, and where it was recorded, signs eased after stopping the medicine in 76% of cases.
1,781Reports
46%Marked serious
34%Only medicine involved
24%Recovered
12%Died or euthanised
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About this medicine
Methimazole treats an overactive thyroid in cats.
Most reported side effects
Share = percentage of this medicine's reports that mention the problem. One report can list several problems.
Reports that it didn't work
Some reports are about the medicine not working (for example a cat still getting fleas or heartworm), not about a side effect.
How soon problems started
Time from the first dose to the first sign, where both dates were reported (1,322 reports).
How the animals did
Breeds named most often
Popular breeds appear more often because there are more of them.
- Domestic Shorthair 1,177 reports
- Domestic Longhair 167 reports
- Domestic Mediumhair 70 reports
- Domestic 52 reports
- Siamese 33 reports
- Maine Coon 25 reports
- Cat (other) 22 reports
- Ragdoll 8 reports
- Russian 7 reports
- Manx 6 reports