Methimazole

Methimazole is used for:

Treating an overactive thyroid gland and treating or preparing the overactive thyroid gland for surgery. It may also be used when your doctor has advised against the removal of the thyroid. It may also be for other conditions as determined by your doctor.

Methimazole is an antithyroid agent. It works by inhibiting the production of thyroid hormone. Thyroid hormones are produced and released by the thyroid gland and regulate the body's metabolism.

Do NOT use Methimazole if:

• you are allergic to any ingredient in Methimazole
• you are breast-feeding

Contact your doctor or health care provider right away if any of these apply to you.

Before using Methimazole:

Some medical conditions may interact with Methimazole. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have bone marrow or liver problems
• if you have exfoliative dermatitis (widespread redness and scaling of the skin)

Some MEDICINES MAY INTERACT with Methimazole. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Anticoagulants (eg, warfarin), beta-blockers (eg, propranolol), digitalis glycosides (eg, digoxin), or theophylline because the risk of their side effects may be increased by Methimazole
• Anticoagulants (eg, warfarin), corticosteroids (eg, hydrocortisone), or digitalis glycosides (eg, digoxin) because their effectiveness may be decreased by Methimazole

This may not be a complete list of all interactions that may occur. Ask your health care provider if Methimazole may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use Methimazole:

Use Methimazole as directed by your doctor. Check the label on the medicine for exact dosing instructions.

• Take Methimazole by mouth with or without food. If stomach upset occurs, take with food to reduce stomach irritation.
• Take Methimazole on a regular schedule around the clock, unless your doctor tells you otherwise.
• If you miss a dose of Methimazole, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.

Ask your health care provider any questions you may have about how to use Methimazole.

Important safety information:

• Methimazole may cause drowsiness, dizziness, or lightheadedness. These effects may be worse if you take it with alcohol or certain medicines. Use Methimazole with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.
• Lab tests, including thyroid and liver function tests, complete blood cell counts, and blood clotting tests (eg, PT, INR), may be performed while you use Methimazole. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
• PREGNANCY and BREAST-FEEDING: Methimazole has been shown to cause harm to the fetus. If you think you may be pregnant, contact your doctor. You will need to discuss the benefits and risks of using Methimazole while you are pregnant. Methimazole is found in breast milk. Do not breast-feed while taking Methimazole.

Possible side effects of Methimazole:

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Change in taste; dizziness; drowsiness; headache; joint pain; lightheadedness; muscle pain; nausea; numbness and tingling; stomach upset; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); changes in appetite; dark urine; fainting; fast or irregular heartbeat; fever, chills, or persistent sore throat; severe or persistent headache, nausea, or vomiting; stomach pain; tremor; unusual bruising or bleeding; unusual hair loss; unusual tiredness or weakness; vision changes; yellowing of the skin or eyes.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

See also: Methimazole side effects (in more detail)

If OVERDOSE is suspected:

Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center, or emergency room immediately. Symptoms may include chest pain; fever; headache; joint pain; nausea; stomach discomfort; swelling; vomiting.

Store Methimazole at room temperature, between 68 and 77 degrees F (20 and 25 degrees C). Brief storage at temperatures between 59 and 86 degrees F (15 and 30 degrees C) is permitted. Store away from heat, moisture, and light. Do not store in the bathroom. Keep Methimazole out of the reach of children and away from pets.

General information:

• If you have any questions about Methimazole, please talk with your doctor, pharmacist, or other health care provider.
• Methimazole is to be used only by the patient for whom it is prescribed. Do not share it with other people.
• If your symptoms do not improve or if they become worse, check with your doctor.
• Check with your pharmacist about how to dispose of unused medicine.

This information is a summary only. It does not contain all information about Methimazole. If you have questions about the medicine you are taking or would like more information, check with your doctor, pharmacist, or other health care provider.