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Propylthiouracil (By mouth)

Propylthiouracil (proe-pil-thye-oh-URE-a-sil)

Treats Graves' disease and hyperthyroidism (too much thyroid hormone from the thyroid gland) in patients who have already been treated with other medicines (such as methimazole) that did not work well.

Brand Name(s):

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

You should not use this medicine if you have had an allergic reaction to propylthiouracil, or if you are pregnant or breastfeeding.

How to Use This Medicine:


  • Your doctor will tell you how much medicine to use. Do not use more than directed.
  • It is best to take propylthiouracil at the same time each day. If you take more than one tablet every day, try to take the medicine at evenly spaced intervals, such as every 12 hours if you take it two times a day, or every 8 hours if you take it three times a day.

If a dose is missed:

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine:

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are also using amiodarone (Cordarone®), certain blood pressure medicine (such as atenolol, metoprolol, propranolol, Inderal®, or Toprol®), potassium supplements, a blood thinner (such as warfarin, Coumadin®), theophylline (Theo-Dur®), or digoxin (Lanoxin®).
  • Talk to your doctor before getting any vaccines (such as flu shots). Also, other people living in your home should not get oral polio vaccine while you are using this medicine. There is a chance they could pass on the polio virus to you.

Warnings While Using This Medicine:

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.
  • Make sure your doctor knows if you have liver disease.
  • It may take several days or weeks for propylthiouracil to start working. Do not stop using the medicine without talking to your doctor.
  • This medicine may make you bleed, bruise, or get infections more easily. Take precautions to prevent illness and injury. Wash your hands often.
  • Liver problems may occur with this medicine. Stop using this medicine and check with your doctor right away if you are having more than one of these symptoms: right upper abdominal or stomach pain or tenderness; clay-colored stools; dark urine; decreased appetite; fever; headache; itching; loss of appetite; nausea and vomiting; skin rash; swelling of the feet or lower legs; unusual tiredness or weakness; or yellow eyes or skin.
  • Tell any doctor or dentist who treats you that you are using this medicine. You may need to stop using this medicine several days before you have surgery or medical tests.
  • Your doctor will check your progress and the effects of this medicine at regular visits. Keep all appointments. Blood tests may be needed to check for unwanted effects.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Changes in menstrual periods.
  • Cough or sore throat.
  • Dark-colored urine or pale stools.
  • Dry, puffy skin.
  • Mouth sores.
  • Nausea, vomiting, loss of appetite, or pain in your upper stomach.
  • Severe fever or chills, or fever that lasts longer than 2 days.
  • Skin rash or itching.
  • Swelling in your neck (thyroid).
  • Unexplained bleeding or bruising.
  • Unusual weakness.
  • Yellowing of your skin or the whites of your eyes.

If you notice these less serious side effects, talk with your doctor:

  • Headache.

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 5/1/2020

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites.

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