Felimazole

Methimazole is a prescription medication used to treat hyperthyroidism (overactive thyroid), a condition in which the thyroid gland produces too much thyroid hormone. Methimazole belongs to a group of drugs called antithyroid drugs. It works by preventing the thyroid from using iodine to make thyroid hormone.

This medication comes in tablet form. It is taken 3 times daily, with or without food.

Common side effects of methimazole include rash, nausea, and vomiting. Methimazole may cause dizziness. Do not drive or operate heavy machinery until you know how this medication affects you.

Methimazole is a prescription medication used to treat hyperthyroidism (overactive thyroid). It is also taken before thyroid surgery or radioactive iodine surgery to lower thyroid hormone levels.

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

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Serious side effects have been reported with methimazole. See the "Drug Precautions" section.

Common side effects of methimazole include the following:

• rash
• nausea
• vomiting
• indigestion
• joint pain
• tingling sensation
• loss of taste
• hair loss
• muscle pain
• headache
• vertigo
• itchiness
• salivary gland inflammation
• lymph node inflammation

This is not a complete list of methimazole side effects. Ask your doctor or pharmacist for more information.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• a beta blocker such as acebutolol (Sectral), atenolol (Tenormin), betaxolol (Kerlone), bisoprolol (Zebeta), carvedilol (Coreg), esmolol (Brevibloc), labetalol (Trandate), metoprolol (Lopressor, Toprol XL), nadolol (Corgard), nebivolol (Bystolic), penbutolol (Levatol), propranolol (Inderal), sotalol (Betapace), timolol (Blocadren)
• digoxin (Digitek, Lanoxin)
• theophylline (Theo-24,  Theobid, Theo-Dur, Theolair, Elixophyllin, Elixophylline, Quibron-T, Uniphyl)
• warfarin (Coumadin, Jantoven)

This is not a complete list of methimazole drug interactions. Ask your doctor or pharmacist for more information.

Serious side effects have been reported with methimazole including:

• low white blood cells and low blood platelets. This can increase the risk of infection or bleeding. Your doctor will monitor for this side effect by using a simple blood test. Tell your doctor right away if you have signs of low blood cells including:
  • infections
  • sore throat
  • fever
  • bruising or bleeding easily
• serious liver problems. Tell your doctor right away if you experience these symptoms:
  • stomach pain or tenderness 
  • clay-colored stools
  • dark urine
  • decreased appetite
  • itching

Do not take methimazole if you are:

• allergic to methimazole
• breastfeeding

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of methimazole, there are no specific foods that you must exclude from your diet when receiving this medication.

Before taking methimazole, tell your doctor about all of your medical conditions. Especially tell your doctor if you:

• are allergic to methimazole
• have liver disease
• have a bleeding disorder
• are pregnant or breastfeeding

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Methimazole falls into category D. It has been shown that use of methimazole in pregnant women caused some babies to be born with problems. However, in some serious situations, the benefit of using this medication may be greater than the risk of harm to the baby.

Tell your doctor if you are breastfeeding or plan to breastfeed.

Methimazole has been detected in human breast milk. Because of the possibility for adverse reactions in nursing infants from methimazole, a choice should be made whether to stop nursing or to stop use of this medication. The importance of the drug to the mother should be considered.

• Take methimazole exactly as prescribed.
• This medication comes in tablet form and is usually taken 3 times daily.
• Methimazole can be taken with or without food.
• If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose.

Take methimazole exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The methimazole dose your doctor recommends will be based on the following:

• the condition being treated
• other medical conditions you have
• other medications you are taking
• how you respond to this medication
• your weight (children)

The recommended starting daily dosage is 15 mg for mild hyperthyroidism, 30 to 40 mg for moderately severe hyperthyroidism, and 60 mg for severe hyperthyroidism, divided into 3 doses at 8-hour intervals.

The maintenance dosage is 5 to 15 mg daily.

If you take too much methimazole, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

• Store at room temperature between 15° and 30°C (59° and 86°F).
• Keep this and all medications out of the reach of children.