Precautions

Drug information provided by: Merative, Micromedex®

It is very important that your doctor check your or your child's progress at regular visits to make sure that the medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

Using this medicine during the first three months of your pregnancy can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away.

In very rare situations, methimazole can temporarily lower the number of white blood cells in your blood, which increases the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

  • If you can, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
  • Check with your doctor immediately if you notice any unusual bleeding or bruising, black, tarry stools, blood in the urine or stools, or pinpoint red spots on your skin.
  • Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
  • Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
  • Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.
  • Avoid contact sports or other situations where bruising or injury could occur.

Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin. These could be symptoms of a serious liver problem.

This medicine may cause hypothyroidism (low levels of thyroid hormone in the blood). Check with your doctor right away if you have constipation, a depressed mood, dry skin and hair, feeling cold, hair loss hoarseness or husky voice, muscle cramps and stiffness, slowed heartbeat, weight gain, or unusual tiredness or weakness.

Make sure any doctor or dentist who treats you knows that you are using this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Portions of this document last updated: Feb. 01, 2024

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