methimazole

Generic Name: methimazole (me THIM a zole)

Brand Names: Northyx, Tapazole

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.

What is the most important information I should know about methimazole?

Do not use methimazole if you are pregnant. It could harm the unborn baby. Do not take methimazole if you are breast-feeding a baby. Methimazole can increase your risk of bleeding. If you need to have surgery, tell the surgeon ahead of time that you are using this medication.

Methimazole can lower blood cells that help your body fight infections. This can make it easier for you to bleed from an injury or get sick from being around others who are ill. Your blood may need to be tested often. Visit your doctor regularly.

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. Keep using this medication even if you feel fine or have no symptoms of hyperthyroidism. You may need to keep taking methimazole long term to control your condition. Stopping the medication could cause your symptoms to return.

What should I discuss with my healthcare provider before taking methimazole?

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;


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  a blood cell disorder; or

  
  


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  a weak immune system.

  
  

FDA pregnancy category D. Do not use methimazole if you are pregnant. It could harm the unborn baby. Use effective birth control, and tell your doctor if you become pregnant during treatment. Methimazole can pass into breast milk and may harm a nursing baby. Do not use methimazole if you are breast-feeding a baby.

How should I take methimazole?

Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Take methimazole with a full glass of water.

Methimazole can be taken with or without food, but you should take it the same way each time.

Methimazole can increase your risk of bleeding. If you need to have any type of surgery, tell the surgeon ahead of time that you are using this medication.

Methimazole can lower blood cells that help your body fight infections. This can make it easier for you to bleed from an injury or get sick from being around others who are ill. Your blood may need to be tested often. Visit your doctor regularly.

It is important to use methimazole regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.

Keep using this medication even if you feel fine or have no symptoms of hyperthyroidism. You may need to keep taking methimazole long term to control your condition. Stopping the medication could cause your symptoms to return. Store at room temperature away from moisture and heat.

See also: Methimazole dosage (in more detail)

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

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

What should I avoid while taking methimazole?

Avoid being near people who are sick or have infections. Tell your doctor at once if you develop signs of infection.

Do not receive a "live" vaccine while using 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. Live vaccines include measles, mumps, rubella (MMR), oral polio, chickenpox (varicella), BCG (Bacillus Calmette and Guérin), and nasal flu vaccine.

Methimazole 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 using methimazole and call your doctor at once if you have a serious side effect such as:

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  fever, chills, sore throat, body aches, flu symptoms;

  
  


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  easy bruising or bleeding, unusual weakness;

  
  


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  blood in your urine or stools;

  
  


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  severe blistering, peeling, and red skin rash; or

  
  


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  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:

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  headache, drowsiness, dizziness;

  
  


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  mild nausea, vomiting, or stomach upset;

  
  


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  itching, minor skin rash;

  
  


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  muscle, joint, or nerve pain;

  
  


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  swelling; or

  
  


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  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.

Methimazole Dosing Information

Usual Adult Dose for Hyperthyroidism:

Initial:
Mild hyperthyroidism: 5 mg orally every 8 hours.
Moderately severe hyperthyroidism: 10 mg orally every 8 hours (up to 40 mg per day).
Severe hyperthyroidism: 20 mg orally every 8 hours.

Maintenance:
5 to 15 mg orally daily.

Usual Pediatric Dose for Hyperthyroidism:

Greater than or equal to 1 year:

Initial dose: 0.4 mg/kg/day orally in 3 equally divided doses 8 hours apart.

Maintenance dose: 0.2 mg/kg/day orally in 3 equally divided doses 8 hours apart.

Maximum dose: 30 mg/day.

What other drugs will affect methimazole?

Tell your doctor about all other medicines you use, especially:

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  theophylline (Theo-Dur, Elixophyllin, Uniphyl, and others);

  
  


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  a blood thinner such as warfarin (Coumadin);

  
  


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  digoxin (digitalis, Lanoxin); or

  
  


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  a beta-blocker such as atenolol (Tenormin, Tenoretic), carvedilol (Coreg), labetalol (Normodyne, Trandate), metoprolol (Lopressor, Toprol), nadolol (Corgard), propranolol (Inderal, InnoPran), sotalol (Betapace), and others.

  
  

This list is not complete and other drugs may interact with methimazole. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor.

More methimazole resources

• Methimazole Side Effects (in more detail)
• Methimazole Dosage
• Methimazole Use in Pregnancy & Breastfeeding
• Drug Images
• Methimazole Drug Interactions
• Methimazole Support Group
• 0 Reviews for Methimazole - Add your own review/rating

• methimazole Advanced Consumer (Micromedex) - Includes Dosage Information


• Methimazole Prescribing Information (FDA)


• Methimazole Professional Patient Advice (Wolters Kluwer)


• Methimazole Monograph (AHFS DI)


• Methimazole MedFacts Consumer Leaflet (Wolters Kluwer)


• Tapazole Prescribing Information (FDA)

Compare methimazole with other medications

• Hyperthyroidism

Where can I get more information?

• Your pharmacist can provide more information about methimazole.

See also: methimazole side effects (in more detail)