1 What is Propylthiouracil?

Brand: Propylthiouracil

Generic: Propylthiouracil

Propylthiouracil is a prescription-only antithyroid medicine that decreases the production of thyroid hormone. So, it is used to treat Graves' disease and hyperthyroidism, an overactive thyroid.

Doctors use propylthiouracil before thyroid surgery or radioactive iodine treatment in patients who have not benefitted from other medicines, such as:

  • Methimazole

It is available as:

  • Tablet

2 What to Know Before Using

Before using Propylthiouracil, you must know all about the risks and complications associated with it. Together with your doctor, you can decide whether the medication will provide you more goods than the harms.

Here are some factors to be considered before deciding to use this medicine:

  • Allergies: Inform your doctor about the allergies you have, such as to this medication, other medications, or to foods, dyes, or preservatives.
  • Pediatric: It causes severe liver problems. So its use in kids is reserved only for the condition where other medicines (methimazole), surgery, or radioactive iodine therapy have failed.
  • Geriatric: Not enough geriatric studies have been conducted. So, it’s not clear if using propylthiouracil is safe or effective in elderly.
  • Pregnancy: Propylthiouracil falls under category D for all trimesters meaning that its use during pregnancy is risky, but may be recommended in a serious situation after assessing the risk to benefit ratio.
  • Breastfeeding: Since propylthiouracil is secreted in breast milk, consult your doctor if you are breastfeeding.
  • Drug Interactions: Taking two medicines together can be harmful due to possible interactions. In other cases, even if there is a possible interaction between two medicines your doctor may advise you to take them together after adjusting the dose or issuing precautions. Here is a list of the medicines which in general are not recommended to be used with propylthiouracil. Inform your doctor if you are using any of these medicines:

        o Carbamazepine
        o Clozapine
        o Methimazole

Though usually not recommended, your doctor may decide, after adjusting dose or frequency of one or both medicines, to use propylthiouracil with any of the following medicines:

        o Acenocoumarol
        o Anisindione
        o Dicumarol
        o Phenindione
        o Phenprocoumon
        o Warfarin

  • Other Interactions: Taking your medicine together with certain foods or items such as alcohol or tobacco may cause undesirable interactions. Talk to your doctor to know if using this medicine with food, alcohol, or tobacco is safe.
  • Medical Problems: Certain medical conditions might influence the effects (both positive and adverse) and action of propylthiouracil. DO NOT forget to inform your doctor about the following conditions:

        o Blood or bone marrow disorders such as agranulocytosis, aplastic anemia, thrombocytopenia.
        o Liver disease: Propylthiouracil may worsen liver disease. Therefore, use with caution.

3 Proper Usage

To use Propylthiouracil properly, you must follow all instructions given by your doctor. Strictly follow your doctor and don’t take more, for longer or more frequently than recommended.

If your doctor advises you to take this medicine 3 times a day, it means you have to take it every 8 hours. Manage your time accordingly.


For best results, follow your doctor to know what amount of medicine you should take in a single dose. The doses of a medicine can differ according to the conditions for which it is being prescribed. If not stated otherwise, the doses here refer to an average dose. Remember your doses can differ.

The doses of tablets for treatment of hyperthyroidism are:

  • Adults: Start with 300 to 900 milligrams (mg) daily in three divided doses to be taken every 8 hours, followed by a maintenance dose of 100 to 150 mg daily.
  • Children 6 years and older: Start with 50 mg daily in three divided doses to be taken every 8 hours, then the dose may be adjusted by your doctor.
  • Children up to 6 years: Your doctor will decide both use and dose of the drug.

Missed Dose:

Take your missed dose once you remember but avoid it if it’s time to take your next dose, and follow your normal dosing schedule. Avoid taking double doses to make up for the missed dose.


  • Store in a closed container at room temperature.
  • Keep away from heat, moisture, and direct light.
  • Do not freeze.
  • Keep away from children.
  • Discard any unused or expired medicines.

4 Precautions to Take

In using Propylthiouracil, you must be careful and take some precautions as advised by your doctor. Your progress should be regularly monitored to look for some undesirable side effects which can be checked by blood tests, if necessary.

Here are some points to consider:

  • Using propylthiouracil during pregnancy may be risky for baby in your womb. Avoid getting pregnant by using appropriate contraceptive measures. If you suspect of getting pregnant, inform your doctor immediately.
  • Propylthiouracil can temporarily reduce white blood cell count making you more susceptible to infections. Therefore, you:

        o May avoid sick people, as far as possible.
        o May visit your doctor immediately if you develop fever or chills, cough or hoarseness, lower back pain, or pain during urination.
        o Wash your hands frequently and avoid touching your eyes or the inside of your nose without washing hands.
        o Don’t get vaccinated during or after propylthiouracil treatment to avoid getting infected by the microorganisms present in the vaccine. Stay away from the person who has recently been vaccinated against polio.
        o Wear a protective mask whenever possible.

  • Propylthiouracil can reduce platelet count making you prone to bleeding. So,

        o Consult your doctor immediately if you notice abnormal bleeding or easy bruising, black, tarry stools or bloody urine or stool.
        o Take care while using toothbrushes, dental floss, and toothpicks.
        o Do not plan a dental appointment without consulting your doctor.
        o Use sharp objects such as safety razor or fingernail or toenail cutters carefully and don’t get cut.
        o Stay away from activities that increase the risk of bruising or injury, such as contact sports.

  • This medicine might also cause liver problems. Immediately discontinue the medicine and consult your doctor if you have:

        o Abdominal pain
        o Clay-colored stools
        o Pale urine
        o Reduced hunger
        o Fever
        o Headache
        o Itching
        o Swelling of the feet or lower legs
        o Excessive tiredness
        o Yellowish eyes or skin

  • Consult your doctor about using other prescription or nonprescription medicines and herbal or vitamin supplements while taking propylthiouracil.

5 Potential Side Effects

As with many medications, there are several potential side effects associated with Propylthiouracil.

Consult your doctor immediately if you experience any of the following side effects:

More common:

Less common:

  • Dark urine
  • Headache
  • Light-colored stools
  • Abdominal pain
  • Yellowish eyes and skin

Seek emergency medical care if you notice any of the following symptoms of overdose:

  • Bloody, black, or tarry stools
  • High fever
  • Itching
  • Dark skin
  • Swellings

Mild and non-serious side effects usually go away on their own without requiring medical intervention. You may also ask your doctor to learn more about how you may prevent or reduce the side effects.

Talk to your doctor if the side effects persist or worry you, including:

  • Abnormal hair thinning
  • Altered taste
  • Dizziness
  • Drowsiness
  • Hives or welts
  • Discomfort in the chest, upper stomach
  • Sore throat
  • Skin rash

The side effects of the medicine are not limited to the ones listed above. Call your doctor immediately if you experience any side effects that are uncommon or worry you. To report side effects to the FDA, contact at 1-800-FDA-1088.

6 Related Clinical Trials