Methimazole
TapazolePubChem CID 1349907 · 3D model
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Blocks the enzyme the thyroid needs to manufacture new hormone, without affecting hormone that's already been made and is circulating in the blood — the opposite move from levothyroxine, also on this site, which adds hormone directly.
How it works
Your thyroid makes its hormone using an enzyme that attaches iodine to a protein and links the pieces together. Methimazole blocks that enzyme, so the thyroid can't manufacture new hormone — but it doesn't touch hormone that's already been made and is sitting in the gland or already circulating in the blood, so it takes time to work as the body gradually uses up what's already on hand. This is the opposite of levothyroxine, also on this site, which adds hormone directly rather than stopping the body from making its own.
What it’s used for
Used to treat an overactive thyroid, including Graves' disease, sometimes as long-term therapy that can lead to lasting remission. Also used short-term to calm an overactive thyroid before surgery or radioactive iodine treatment.
- Mechanism
- Thyroid peroxidase (TPO) inhibitor
- Drug class
- Small molecule
- Therapeutic area
- Endocrine