Methimazole
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Drug Status
Government Approvals
US(FDA)
WHO Essential Medicine
YES
Known Teratogen
Possible
Pharmaceutical Class
Thyroid Hormone Synthesis Inhibitor
Controlled Drug Substance
No
Methimazole
Summary
Methimazole is used to treat an overactive thyroid, also known as hyperthyroidism. This condition can be caused by Graves' disease or toxic multinodular goiter, which are disorders where the thyroid gland produces too much thyroid hormone.
Methimazole works by stopping your body from making too much thyroid hormone. It doesn't get rid of thyroid hormone that's already in your body, it only prevents your body from making more.
Methimazole is usually taken three times a day with food. Adults start with 15mg daily for mild cases, increasing to 30-40mg for moderate and 60mg for severe cases. The usual daily range is 5-15mg.
The most common side effect of Methimazole is an upset stomach. Less common but serious side effects include problems with blood cell production, fever, liver inflammation, and inflammation of blood vessels.
Methimazole can harm a developing baby during the first three months of pregnancy. It can also cause a dangerously low white blood cell count and damage the liver. Don't take it if you're allergic to it.
Indications and Purpose
How does Methimazole work?
Methimazole is a medication used to treat an overactive thyroid (hyperthyroidism). It works by stopping your body from making too much thyroid hormone. The medicine is swallowed and absorbed into your body through your gut. Your liver processes it, and it's then removed from your body through your urine. Importantly, methimazole doesn't get rid of thyroid hormone that's already in your body; it only prevents your body from making more. Hyperthyroidism is a condition where the thyroid gland produces excessive amounts of hormones, leading to symptoms like rapid heartbeat, weight loss, and nervousness. Therefore, methimazole helps control these symptoms by reducing the production of these excess hormones.
Is Methimazole effective?
Yes, Methimazole is highly effective in controlling hyperthyroidism. Clinical studies show significant improvement in symptoms and hormone levels in the majority of patients. Its success depends on adherence to the prescribed regimen and regular monitoring.
What is Methimazole?
Methimazole treats hyperthyroidism (overactive thyroid). An overactive thyroid makes too much thyroid hormone. This medicine is also used before thyroid surgery or radioactive iodine treatment for hyperthyroidism. You usually take methimazole three times a day with food. It's very important to follow your doctor's instructions exactly on how much to take and when. Never change your dosage without talking to your doctor first. They will determine the right dose for your specific needs. This information is for general knowledge and does not replace advice from your doctor or other healthcare professional.
Directions for Use
For how long do I take Methimazole?
The duration of treatment varies but typically lasts 12–18 months, depending on the severity of hyperthyroidism and response to therapy. Your doctor will regularly assess your thyroid function and adjust the dosage as needed.
How do I take Methimazole?
Methimazole tablets are usually taken three times a day, about every eight hours, with food. There are no special dietary rules. If you miss a dose, take it as soon as you remember, unless it's almost time for your next dose. Never take two doses at once to make up for a missed one. Methimazole is a medication.
How long does it take for Methimazole to start working?
Methimazole starts reducing thyroid hormone levels within 1–2 weeks, but full effects may take 4–8 weeks. Regular blood tests will monitor your thyroid hormone levels during this period.
How should I store Methimazole?
Methimazole storage instructions: Store methimazole at room temperature, away from heat and dampness (like a bathroom). Keep it in its original, tightly sealed container, out of reach of children. Disposal: The best way to dispose of leftover methimazole is through a drug take-back program. These programs are often run by pharmacies or local government agencies. Check with your pharmacist or local waste/recycling department to find one near you. If a take-back program isn't available, the FDA website offers safe disposal alternatives. Never flush medicine down the toilet. *Methimazole:* A medication used to treat certain thyroid conditions.
What is the usual dose of Methimazole?
Adults start with 15mg daily for mild cases, increasing to 30-40mg for moderate, and 60mg for severe cases. The usual daily range is 5-15mg.Children's starting dose is calculated based on their weight: 0.4 milligrams (mg) of methimazole per kilogram (kg) of body weight, given in three separate doses. For example, a 20kg child would start with 8mg/day (0.4mg/kg 20kg = 8mg). The maintenance dose (the amount needed once the thyroid is under control) is about half the initial dose. A kilogram (kg) is a unit of weight approximately equal to 2.2 pounds.
Warnings and Precautions
Can I take Methimazole with other prescription drugs?
Methimazole may interact with anticoagulants (e.g., warfarin), increasing bleeding risk, and beta-blockers, requiring dose adjustments. Always inform your doctor about all medications you take to avoid interactions.
Can Methimazole be taken safely while breastfeeding?
Methimazole passes into breast milk, but studies haven't shown any harm to babies who are breastfed while their mothers take it. However, because it's a medication that affects the thyroid (a gland that controls metabolism), a doctor will want to regularly check the baby's thyroid function with blood tests. These checks are typically done weekly or every two weeks to make sure the baby's thyroid is working correctly. This monitoring is a precaution, not an indication that there's necessarily a problem. The frequency of monitoring will depend on the baby's individual situation and doctor's recommendation.
Can Methimazole be taken safely while pregnant?
Methimazole use during pregnancy is risky. This medicine crosses the placenta and can harm the developing baby, potentially causing birth defects like skin problems (aplasia cutis), facial abnormalities (craniofacial), digestive system issues (gastrointestinal), and omphalocele (a belly button defect). The baby might also develop a goiter (enlarged thyroid gland) or cretinism (severe mental and physical retardation). The risk is greatest in the first three months of pregnancy. Doctors should use the lowest possible dose. Other medicines may be better, especially early in pregnancy. Careful monitoring of the mother's and baby's thyroid function is vital. The doctor might reduce the dose or stop it before the baby is born.
Is it safe to drink alcohol while taking Methimazole?
Alcohol in moderation is generally safe, but excessive drinking may worsen liver function and interact with the medication. Consult your doctor for personalized advice.
Is it safe to exercise while taking Methimazole?
Exercise is safe and beneficial for most patients. However, if you experience fatigue or other symptoms of hyperthyroidism, consult your doctor before starting a new exercise routine.
Is Methimazole safe for the elderly?
Methimazole can be safely used in elderly patients, but they may require lower doses and close monitoring due to a higher risk of side effects, such as liver dysfunction or blood disorders.
Who should avoid taking Methimazole?
Methimazole is a medication with several important warnings. Don't take it if you're allergic to it. It can harm a developing baby during the first three months of pregnancy, possibly causing birth defects. A very serious side effect is agranulocytosis (a dangerously low white blood cell count), indicated by fever or sore throat. **Report these symptoms to your doctor immediately.** Methimazole can also damage the liver (hepatotoxicity), so liver function tests may be needed. Rarely, it can cause vasculitis (inflammation of blood vessels), which can be severe. Keep methimazole out of reach of children. Always talk to your doctor about any concerns or side effects.
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