Propylthiouracil (Oral)

Propylthiouracil is used to treat an overactive thyroid and Graves’ diseases. It may also be used before thyroid surgery or before radioactive iodine treatment for patients who have already taken other medications, without effect.


Propylthiouracil is prescribed for the treatment of hyperthyroidism and Graves disease. It is also prescribed to patients with a toxic multinodular goiter for whom other medications did not work well, following thyroid surgery or before radioactive iodine treatment. Propylthiouracil is generally recommended for reducing the severity of hyperthyroidism symptoms, such as lowered pulse rate and weight gain. It may be used as a short-term coordinating therapy. Treatment time ranges from approximately six months to several years, usually averaging one year.

Propylthiouracil functions as an antithyroid agent that works by making it more difficult for the body to utilize iodine to produce thyroid hormones. The two hormones produced by the thyroid gland are formed by combining iodine and a specific protein called thyroglobulin, using an enzyme called peroxidase. Propylthiouracil keeps iodine and thyroglobulin from interacting to form these hormones in excess. It does not block any effects of thyroid hormone produced prior to use of Propylthiouracil. This medication is available only with prescription by a physician.

Conditions Treated

Type Of Medicine

  • Antithyroid agent

Side Effects

Side effects have been known to occur with the use of Propylthiouracil. Though not all side effects may occur, some may require immediate medical attention. Propylthiouracil is generally tolerated well, with side effects occurring in one in 100 patients. The more common side effects of Propylthiouracil include the following.

  • Dark, tarry stools
  • Cough
  • Chest pain
  • Chills
  • Difficulty tasting food
  • Hair loss or hair whitening
  • Fever
  • Numbness or tingling in the hands and feet
  • Pain while urinating
  • Shortness of breath
  • Sore throat
  • Sores or white spots on or around the lips and mouth
  • Swollen glands, particularly those found around the neck
  • Unusual fatigue or weakness
  • Bleeding or Bruising

Less common side effects of Propylthiouracil include the following:

  • An overall feeling of illness, weakness or general discomfort
  • Headaches
  • Light-colored stools
  • Nausea
  • Vomiting
  • Long-term stomach pain
  • Pain in the upper right abdomen
  • Yellow eyes and skin

Other side effects not included in this list may occur. Any additional symptoms should be reported to the prescribing physician.

Using Propylthiouracil during pregnancy may cause side effects to an unborn baby. The benefits and risks should be discussed with the prescribing physician. Propylthiouracil is generally preferred over methimazole in women who are pregnant or nursing.


As with any medication, Propylthiouracil should only be used by the person it is prescribed to and should be used as directed. A medication guide should be provided by the pharmacist each time the prescription is filled or refilled.

This medication comes in tablet form and should be taken orally. This medication is typically prescribed for use three times a day, every eight hours, with or without food. Dosage may be changed based on individual circumstances or response to current treatment.

The condition will not improve quickly with the use of additional medication. It must be used regularly to gain the most benefit from it. This medication should not be stopped without consultation with a physician. Because this medication works best when constantly present in the blood, doses should not be missed. Doses should be equally spaced and taken about eight hours apart.

The amount of medication prescribed will be different for different patients. Doctors orders will be printed on the label. Adults are typically prescribed 300mg, which is generally the initial dose, or 900mg daily, divided into three equal doses, taken every eight hours. A 900 mg dose is usually only prescribed for patients with large goiters. The maintenance dose prescribed after initial treatment is typically 100mg or 150 mg daily. Children over the age of six are generally prescribed 50mg daily, divided into three equal doses, taken eight hours apart. The use of Propylthiouracil in children under the age of six is not recommended. Children taking Propylthiouracil should be closely monitored by their physician throughout the entire course of their treatment.

The prescribing physician may make changes to the dosage at any point during treatment. The dosage is often decreased once hyperthyroidism is controlled. If a dose is missed, it should be taken as soon as possible. If it is almost time for the next dose, the missed dose should be skipped and the regular dosing schedule resumed. Double doses should not be taken.

In the case of an overdose, immediate medical attention should be sought. Symptoms of an overdose include high fever, bloody, black or tarry stools, itchy skin, pale skin, and swelling. If any of these symptoms occur, immediate medical attention should be sought.

Major Drug Interactions

Taking another drug along with Propylthiouracil can lead to unwanted interactions. In some cases, medications can be used together, even if interactions occur. The dosage of another medication may be changed, to make it more compatible with Propylthiouracil. While taking Propylthiouracil, it is particularly important to inform the prescribing physician of any medications, herbs or nutritional supplements that may be taken.

Continuing to take this medication along with other drugs should be done only under consultation with the prescribing physician. Oral blood thinners are most commonly known to interact with Propylthiouracil. The following drugs may interact with Propylthiouracil:

  • Acenocoumarol
  • Anisindione
  • Dicumarol
  • Phenindione
  • Phenprocoumon
  • Warfarin

This list is not comprehensive, and additional medications may also interact with the medication. Along with drug interactions, alcohol and tobacco may also interfere with Propylthiouracil. Patients who drink alcoholic beverages or who use tobacco products should inform the prescribing physician, who may recommend that use is either reduced or eliminated during and prior to treatment. Allergies to the medication may occur. Certain ingredients, such as food dyes and preservatives included in the manufacture of Propylthiouracil, may also cause interaction with other drugs.

Since hyperthyroidism can cause an increased elimination of beta blockers, once hyperthyroidism has been reversed by taking Propylthiouracil, the excretion of beta blockers may return to normal, so less will be needed to achieve the same effect. Digoxin blood levels may also increase with the presence of hyperthyroidism, and when reversed, a smaller dose of digoxin may be indicated. Likewise, theophylline elimination may decrease when hyperthyroidism is reversed, and a reduced dose may be necessary to prevent toxicity.


Propylthiouracil should not be taken with other medications unless recommended by the prescribing physician. Allergies to the medication or its inactive ingredients may occur. There are reports of severe liver problems happening with the use of Propylthiouracil.

This medication may be used for pediatric patients, but it is only recommended for children when other medications such as methimzole, or treatments such as surgery or radioactive iodine therapy, have not worked. There is no information available on potential negative effects of Propylthiouracil when used by geriatric patients.

It is recommended that Propylthiouracil is only used by pregnant women when the benefits of treatment with the medication outweigh the risks. Studies have shown that Propylthiouracil may pose a significant risk to the fetus. This medication poses minimal risk to infants when used during breastfeeding. The prescribing physician should be notified if the patient is pregnant, plans to become pregnant or is breastfeeding.

A history of other medical problems may affect the use of Propylthiouracil, so all previous medical history should be discussed with the prescribing physician. It is especially to report any previous history of blood or marrow problems such as agranulocytosis, aplastic anemia and thrombocytopenia, or liver disease.

Patients should discuss any dietary sources of iodine, including iodized salt and shellfish with the prescribing physician.

A physician should monitor users of Propylthiouracil during the entire course of treatment. Regular visits to a physician are recommended, along with blood tests that can rule out any negative effects.

Because this medication can harm an unborn baby, using an effective form of birth control while taking this medication is suggested. Women who are pregnant or who might become pregnant should inform their physician before taking Propylthiouracil. The primary effect on an unborn baby from the transplacental passage of Propylthiouracil is the development of mild hypothyroidism, particularly when close to term. This is usually resolved within a few days, with no outside treatment needed. This hypothyroidism may manifest as a goiter in the newborn, as the result of increased levels of thyrotropin.

Propylthiouracil may temporarily lower the number of white blood cells found in blood, which increases the change of infection. This medication may also lower the number of platelets, which are needed for proper blood clotting. If these events occur, certain precautions can reduce the risk of bleeding or infection. These precautions include those described in the following list.

  • Taking care to avoid people with infections. If symptoms of an infection, such as fever, chills, cough, hoarseness, back or side pain or painful urination occur, these should be reported to the prescribing physician.
  • Reporting any unusual bruising or bleeding, blood in the stools or urine or spots on the skin.
  • Reporting black, tarry stools
  • Using care when brushing teeth, flossing or using toothpicks. A different way of cleaning teeth may be recommended by a physician or dentist during the use of this medication.
  • Use of this medication should be reported to a dentist before any dental procedures are completed.
  • Care should be used around sharp objects such as razor blades or nail clippers.
  • Contact sports or other injuries where bruising or injury could occur should be avoided.

Immunizations should not be given when a patient is taking Propylthiouracil, without the approval of the prescribing physician. Propylthiouracil could lower the resistance and cause the infection that the immunization is meant to prevent. The patient and those living in their household should not take an oral polio vaccine. Those who have recently taken an oral polio vaccine should wear a mask when around the patient and not get too close to them.

Significant liver problems may occur while taking this medication. Propylthiouracil should be stopped and a physician consulted if the patient experiences abdominal or stomach pain or tenderness, clay-colored stools, decreased appetite, blood in the urine, fever, itching, loss of appetite, nausea and vomiting, skin rash, swelling of the feet or lower legs, excessive fatigue or yellowing of the eyes or skin.

Before any surgery or medical procedure, the physician in charge should be notified of the use of this medication. Taking Propylthiouracil along with the medications used during surgery could increase the risk of side effects.

The prescribing physician should be informed if the patient is allergic to this or any other medication or any of the ingredients contained in Propylthiouracil. A complete list of ingredients can be found in the Propylthiouracil medication guide.

It is important to inform the prescribing physician of the use of anticoagulants and beta blockers. The dosage of certain medications may be changed during the course of treatment with Propylthiouracil.

The prescribing physician should be informed if the patient has every had leukopenia, thrombocytopenia or aplastic anemia. Any condition that affects the number of white blood cells that are produced by the body should also be reported, as should any prior history of liver disease.

Throughout treatment, the patient should be continually assessed for symptoms of hypothyroidism, which include constipation, intolerance to cold, dry skin, constipation, headaches, weakness and fatigue. The physician should also be checked regularly for skin rashes or swelling of the cervical lymph nodes.

Patients taking Propylthiouracil should monitor their weight two to three times weekly and report any significant changes to the prescribing physician.

This medication may cause drowsiness, so certain activities, such as driving should be avoided until the response to Propylthiouracil is known.

Carrying identification describing the use of Propylthiouracil as part of a medication regimen is suggested.

No other medications, including over the counter drugs, herbs or nutritional supplements should not be taken while using Propylthiouracil unless first discussed with a physician.


Propylthiouracil should be stored in a closed container kept at room temperature, or approximately 77°F, and away from moisture, heat and direct light and should not be frozen. All tablets should be taken as prescribed and kept out of the reach of children and pets. Any unused medication should be disposed of and any outdated medication should not be kept. A healthcare professional should be consulted on the proper disposal of any unused medication.


Propylthiouracil is an oral antithyroid medication that comes in the form of a tablet. It is used to treat hyperthyroidism and Graves disease. It may also be prescribed to patients who recently had thyroid surgery or prior to radioactive iodine treatment for patients with a toxic multinodular goiter when other medications have not worked effectively.

Propylthiouracil works by making it more difficult for the body to use iodine and produce thyroid hormone. It does not block the effects of any thyroid hormone that was produced by the body prior to the use of Propylthiouracil. The medication is generally well tolerated, with some common side effects reported.

This medication should only be used under the supervision of a physician. It may lower the amount of white blood cells found in the blood, which increases the risk of infection. For this reason, particular care should be taken to avoid infection. This includes not taking vaccines and avoiding people who have recently received an oral polio vaccine.

Propylthiouracil should not be used when pregnant, unless the patient and physician have determined that the benefits significantly outweigh the risks. This medication may cause irreversible harm to an unborn baby. No risks of breastfeeding have been reported, though the medication is secreted in small amounts through breast milk. Patients should inform their physician if they are pregnant or may become pregnant, prior to taking this medication.

The use of Propylthiouracil in children over the age of 6 may be indicated. Propylthiouracil is prescribed to children in a lower dose, in tablet form. Use of Propylthiouracil in children under the age of 6 is not recommended.

Prior to any medical or dental procedure, the use of Propylthiouracil should be reported to the physician or dentist in charge. Propylthiouracil may interact with certain drugs used during surgery. A medication guide should be provided by the pharmacist with this medication and should be read thoroughly before use. A normal diet can be followed while using Propylthiouracil.

Treatment time will vary based on why Propylthiouracil is prescribed and whether it is considered a primary or adjunct treatment. The average treatment time varies from 6 months to several years, with one year being the average treatment span.