Methimazole

What is methimazole?

Methimazole prevents the thyroid gland from producing too much thyroid hormone.

Methimazole is used to treat hyperthyroidism (overactive thyroid). It is also used before thyroid surgery or radioactive iodine treatment.

Methimazole may also be used for other purposes not listed in this medication guide.

Precautions

Do not use this medication if you are allergic to methimazole.

If you have any of these other conditions, you may need a dose adjustment or special tests to safely take this medication:

liver disease;
a blood cell disorder; or
a weak immune system.

FDA pregnancy category D. This medication can cause harm to an unborn baby. Do not use methimazole without your doctor’s consent if you are pregnant. Tell your doctor if you become pregnant during treatment. Use an effective form of birth control while you are using this medication.

Methimazole can pass into breast milk and may harm a nursing baby. Do not use methimazole if you are breast-feeding a baby.

Avoid being near people who have colds, the flu, or other contagious illnesses. Contact your doctor at once if you develop signs of infection.

Do not receive a "live” vaccine while you are being treated with methimazole, and avoid coming into contact with anyone who has recently received a live vaccine. There is a chance that the virus could be passed on to you.

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Instructions

Seek emergency medical attention if you think you have used too much of this medicine.

Overdose symptoms may include nausea, vomiting, upset stomach, headache, joint pain, fever, itching, swelling, or pale skin and easy bruising or bleeding.

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

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Side Effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop taking methimazole and call your doctor at once if you have any of these serious side effects:

fever, chills, sore throat, body aches, flu symptoms;
easy bruising or bleeding, unusual weakness;
blood in your urine or stools;
severe blistering, peeling, and red skin rash; or
nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Less serious side effects may include:

headache, drowsiness, dizziness;
mild nausea, vomiting, or stomach upset;
itching, minor skin rash;
muscle, joint, or nerve pain;
swelling; or
hair loss.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. You may report side effects to FDA at 1-800-FDA-1088.

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Interactions

Before taking methimazole, tell your doctor if you are using any of the following drugs:

theophylline (Theo-Dur, Elixophyllin, Uniphyl, and others);
a blood thinner such as warfarin (Coumadin);
digoxin (digitalis, Lanoxin); or
a beta-blocker such as acebutolol (Sectral), atenolol (Tenormin), betaxolol (Kerlone), bisoprolol (Zebeta), carteolol (Cartrol), carvedilol (Coreg), esmolol (Brevibloc), labetalol (Normodyne, Trandate), metoprolol (Lopressor, Toprol), nadolol (Corgard), penbutolol (Levatol), pindolol (Visken), propranolol (Inderal, InnoPran), sotalol (Betapace), or timolol (Blocadren).

This list is not complete and there may be other drugs that can interact with methimazole. Tell your doctor about all your prescription and over-the-counter medications, vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start a new medication without telling your doctor.

Other Names

Tapazole, methimazole, and Northyx

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Disclaimer

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.