Before Using

Drug information provided by: Merative, Micromedex®


Tell your doctor if you have ever had any unusual or allergic reaction to medicines in this group or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


This medicine has been used in children and teenagers and, in effective doses, has not been shown to cause different side effects or problems in children than it does in adults.


Elderly people may have an increased chance of certain side effects during treatment. Your doctor may need to take special precautions while you are taking this medicine.


Use of too large a dose during pregnancy may cause problems in the fetus. However, use of the proper dose, with careful monitoring by the doctor, is not likely to cause problems.


These medicines pass into breast milk. (Methimazole passes into breast milk more freely and in higher amounts than propylthiouracil.) However, your doctor may allow you to continue to breast-feed, if your dose is low and the infant gets frequent check-ups. If you are taking a large dose, it may be necessary for you to stop breast-feeding during treatment.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking any of these medicines, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using medicines in this class with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Bupropion
  • Levoketoconazole
  • Macimorelin
  • Methotrexate
  • Pexidartinib
  • Tegafur

Other Interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of medicines in this class. Make sure you tell your doctor if you have any other medical problems, especially:

  • Liver disease—The body may not get this medicine out of the bloodstream at the usual rate, which may increase the chance of side effects.