What is Methimazole?

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  • Written By: Mary McMahon
  • Edited By: Kristen Osborne
  • Last Modified Date: 18 May 2019
  • Copyright Protected:
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Methimazole is a prescription medication most commonly used in the treatment of hyperthyroidism, as it suppresses activity in the thyroid gland and limits the production of thyroid hormones. One brand name used in reference to this medication is Tapazole, and others may be used as well, depending on the region where a patient is receiving care. This medication may not have a curative effect for a patient with hyperthyroidism, depending on the cause of the condition, and patients need to be monitored while they take the medication for signs of complications.

This medication is available in the form of tablets taken orally. Patients on methimazole may experience side effects like skin cracking and peeling, fatigue, nausea, weight loss, stomach pain, joint pain, rashes, and itching. More seriously, patients sometimes develop dizziness, low white blood cell counts, and immune dysfunction. While side effects are relatively rare, patients need to be alert and they should report any side effects experienced to their doctors. This medication can also interact adversely with some other prescription and over-the-counter medications. It is important for patients to alert their doctors and pharmacists to all medications they take, in case there is a risk of a drug interaction.


For patients with thyroid cancers, methimazole will control the immediate symptoms of hyperthyroidism, but it will not address the cancer. The patient may need surgery, radiation, and other treatments to remove the thyroid gland or limit its function. In other patients, like people with Grave's disease, the methimazole can manage the condition effectively.

Pregnant and breastfeeding women should not use this medication. Clinical studies have shown that methimazole is dangerous for the developing fetus and can cause birth defects. Women on this medication should take birth control to avoid getting pregnant and should consult a doctor as soon as possible if their birth control fails. Likewise, use of this medication should be discontinued during breastfeeding, as it may harm the infant.

People can store methimazole in a cool, dry place. It should not be kept in a location with a humid environment like the bathroom or kitchen, and should be kept out of reach of other members of the household. In a house where multiple people take medications, it can be helpful to store the drugs separately to avoid accidents, and pill organizers should always be clearly labeled, as well as color coded, so they are not confused.



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