Thiamazole
Thiamazole, also known as methimazole, is a medication used to treat hyperthyroidism. This includes Graves disease, toxic multinodular goiter, and thyrotoxic crisis. It is taken by mouth. Full effects may take a few weeks to occur.
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| Trade names | Tapazole, others |
| Other names | methimazole (USAN US) |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682464 |
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| Routes of administration | By mouth |
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| Pharmacokinetic data | |
| Bioavailability | 93% |
| Protein binding | None |
| Metabolism | Liver |
| Elimination half-life | 5-6 hours |
| Excretion | Kidney |
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| ECHA InfoCard | 100.000.439 |
| Chemical and physical data | |
| Formula | C4H6N2S |
| Molar mass | 114.17 g·mol−1 |
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| Melting point | 146 °C (295 °F) |
| Solubility in water | 275 mg/mL (20 °C) |
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Common side effects include itchiness, hair loss, nausea, muscle pain, swelling, and abdominal pain. Severe side effects may include low blood cell counts, liver failure, and vasculitis. Use is not recommended during the first trimester of pregnancy due to the risk of congenital anomalies, but it may be used in the second trimester or third trimester. It may be used during breastfeeding. Those who developed significant side effects may also have problems with propylthiouracil. Thiamazole is a cyclic thiourea derivative that works by decreasing the production of thyroid hormones.
Thiamazole was approved for medical use in the United States in 1950. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. It is also available in Europe and Asia. In 2020, it was the 206th most commonly prescribed medication in the United States, with more than 2 million prescriptions.