Methimazole Tablets

Methimazole is a medication that treats hyperthyroidism, or high thyroid levels in your body. It decreases the amount of thyroid hormone your body makes. Brand names of this medication are Northyx® and Tapazole®.

What is this medication?

METHIMAZOLE (meth IM a zole) treats high thyroid levels (hyperthyroidism) in your body. It works by decreasing the amount of thyroid hormone your body makes.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

COMMON BRAND NAME(S): Northyx, Tapazole

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What should I tell my care team before I take this medication?

They need to know if you have any of these conditions:

  • Liver disease
  • Low blood counts, like low white cell counts
  • An unusual or allergic reaction to methimazole, other medications, foods, dyes, or preservatives
  • Pregnant or trying to get pregnant
  • Breast-feeding

How should I use this medication?

Take this medication by mouth with a glass of water. Follow the directions on the prescription label. You can take this medication with or without food. However, you should always take it the same way to make sure the effects are the same. Take your doses at regular intervals. Do not take your medication more often than directed. Do not stop taking this medication except on the advice of your care team.

Talk to your care team about the use of this medication in children. Special care may be needed. While this medication may be prescribed for children for selected conditions, precautions do apply.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.

NOTE: This medicine is only for you. Do not share this medicine with others.

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What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What may interact with this medication?

  • Aminophylline
  • Certain medications for high blood pressure, heart disease, irregular heartbeat like metoprolol and propranolol
  • Digoxin
  • Theophylline
  • Warfarin

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

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What should I watch for while using this medication?

Visit your care team for regular checks on your progress. Tell your care team if your symptoms do not start to get better or if they get worse. It may take time for your condition to improve. You will need tests to check your blood counts and to make sure your body is making the right amount of thyroid hormone.

Call your care team for advice if you get a fever, chills or sore throat. Do not treat yourself.

Women should inform their care team if they wish to become pregnant or think they might be pregnant. There is a potential for serious side effects to an unborn child. Talk to your care team for more information.

If you are going to need surgery or other procedure, tell your care team that you are using this medication.

What side effects may I notice from receiving this medication?

Side effects that you should report to your care team as soon as possible:

  • Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
  • Infection—fever, chills, cough, or sore throat
  • Liver injury—right upper belly pain, loss of appetite, nausea, light-colored stool, dark yellow or brown urine, yellowing skin or eyes, unusual weakness or fatigue
  • Low thyroid levels (hypothyroidism)—unusual weakness or fatigue, increased sensitivity to cold, constipation, hair loss, dry skin, weight gain, feelings of depression
  • Unusual weakness or fatigue, fever, headache, skin rash, muscle or joint pain, loss of appetite, pain, tingling, or numbness in the hands or feet

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

  • Change in taste
  • Dizziness
  • Hair loss
  • Headache
  • Nausea
  • Upset stomach

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medication?

Keep out of the reach of children.

Store at room temperature between 20 and 25 degrees C (68 and 77 degrees F). Keep tightly closed. Protect from light. Throw away any unused medication after the expiration date.

NOTE: This sheet is a summary. It may not cover all possible information. If you have questions about this medicine, talk to your doctor, pharmacist, or health care provider.

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Note: Introduction and Additional Common Questions written and medically approved by Cleveland Clinic professionals.

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