Methimazole (patient information)
Why this medication is prescribed
Methimazole is used to treat hyperthyroidism, a condition that occurs when the thyroid gland produces too much thyroid hormone. It is also taken before thyroid surgery or radioactive iodine therapy.
This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.
How this medication should be used
Methimazole comes as a tablet and usually is taken three times a day, approximately every 8 hours, with food. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand.
Special precautions
Before taking methimazole:
- tell your doctor and pharmacist if you are allergic to methimazol, lactose, or any other drugs.
- tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially anticoagulants ('blood thinners') such as warfarin (Coumadin), beta blockers such as propranolol (Inderal), diabetes medications, digoxin (Lanoxin), theophylline (Theobid, Theo-Dur), and vitamins.
- tell your doctor if you have or have ever had any blood disease, such as decreased white blood cells (leukopenia), decreased platelets (thrombocytopenia), or aplastic anemia, or liver disease (hepatitis, jaundice).
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. Methimazole should not be used during pregnancy or breast-feeding. If you become pregnant while taking methimazole, call your doctor immediately. Methimazole may harm the fetus.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking methimazole.
Special dietary instructions
Methimazole may cause an upset stomach. Take methimazole with food or milk.
What to do if you forget a dose
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule at evenly spaced, 8-hour intervals. Do not take a double dose to make up for a missed one.
Side effects
Minor side effects
Methimazole may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- skin rash
- itching
- abnormal hair loss
- upset stomach
- vomiting
- loss of taste
- abnormal sensations (tingling, prickling, burning, tightness, and pulling)
- swelling
- joint and muscle pain
- drowsiness
- dizziness
- decreased white blood cells
- decreased platelets
Severe side effects
If you experience any of the following symptoms, call your doctor immediately:
- sore throat
- fever
- headache
- chills
- unusual bleeding or bruising
- right-sided abdominal pain with decreased appetite
- yellowing of the skin or eyes
- skin eruptions
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at http://www.fda.gov/MedWatch/report.htm] or by phone [1-800-332-1088].
Storage conditions needed for this medication
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of emergency/overdose
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
Other information
Keep all appointments with your doctor and the laboratory.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
Brand names
- Tapazole®