Propylthiouracil Side Effects

Medically reviewed by Drugs.com. Last updated on Feb 25, 2025.

Applies to propylthiouracil: oral tablet.

Precautions

It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. You should not become pregnant while you are taking this medicine. If you think you have become pregnant while using the medicine, tell your doctor right away.

Propylthiouracil can temporarily lower the number of white blood cells in your blood, increasing 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.

While you are being treated with propylthiouracil, and after you stop treatment with it, do not have any immunizations (vaccines) without your doctor’s approval. Propylthiouracil may lower your body’s resistance and there is a chance you might get the infection the immunization is meant to prevent. In addition, other persons living in your household should not take or have recently taken oral polio vaccine since there is a chance they could pass the polio virus on to you. Also, avoid other persons who have taken oral polio vaccine. Do not get close to them, and do not stay in the same room with them for very long. If you cannot take these precautions, you should consider wearing a protective face mask that covers the nose and mouth.

Liver problems may occur while you are using 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.

Before having any kind of surgery, tell the medical doctor in charge that you are using this medicine. Taking propylthiouracil together with medicines used during surgery may increase the risk of side effects.

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.

Serious side effects of propylthiouracil

Along with its needed effects, propylthiouracil may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking propylthiouracil:

Get emergency help immediately if any of the following symptoms of overdose occur while taking propylthiouracil:

Symptoms of overdose

• bloody, black, or tarry stools
• high fever
• itching skin
• pale skin
• swelling

Other side effects of propylthiouracil

Some side effects of propylthiouracil may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

For healthcare professionals

Applies to propylthiouracil: oral tablet.

General adverse events

The more commonly reported adverse events have included nausea, taste perversion, and itching.

Hepatic

• Common (1% to 10%): Asymptomatic liver function test abnormalities (increased serum bilirubin, alanine transaminase and/or alkaline phosphatase concentrations), which are reversible on dose reduction or discontinuation of treatment
• Frequency not reported: Liver injury presenting as hepatitis, liver failure necessitating liver transplantation jaundice (usually cholestatic), hepatic necrosis, hepatic failure^[Ref]

Liver injury resulting in liver failure presenting as hepatitis, liver failure necessitating liver transplantation or resulting in death, has been reported. Cases of liver injury and death were reported in women during pregnancy; two reports of liver failure and death have been received in newborns exposed to this drug in utero.^[Ref]

Immunologic

• Frequency not reported: Vasculitis syndrome, lupus-like syndrome (including splenomegaly and vasculitis), sialadenopathy^[Ref]

Vasculitis resulting in severe complications and death have been reported. These cases have included glomerulonephritis, leukocytoclastic cutaneous vasculitis, alveolar/pulmonary hemorrhage, cerebral angiitis, and ischemic colitis. Most were associated with anti-neutrophilic cytoplasmic antibodies (ANCA)-positive vasculitis.^[Ref]

Hematologic

• Rare (Less than 0.1%): Agranulocytosis, thrombocytopenia, leucopenia, aplastic anemia, pancytopenia, hemorrhage, granulocytopenia
• Frequency not reported: Hypoprothrombinemia, lymphadenopathy^[Ref]

Dermatologic

• Rare (0.01% to 0.1%): Stevens Johnson syndrome, toxic epidermal necrolysis
• Very rare (less than 0.01%): Skin rash, urticaria
• Frequency not reported: Exfoliative dermatitis, erythema nodosum, abnormal loss of hair, pruritus, skin pigmentation, lightening of hair color, lymphadenopathy, mild papular skin rashes, leukocytoclastic cutaneous vasculitis^[Ref]

Gastrointestinal

• Rare (Less than 0.1%): Vomiting
• Frequency not reported: Nausea, vomiting, epigastric distress^[Ref]

Genitourinary

• Frequency not reported: Increase of decrease in urination^[Ref]

Metabolic

• Frequency not reported: Edema^[Ref]

Musculoskeletal

• Frequency not reported: Periarteritis, arthralgia, myalgia, arthritis, myopathy, backache^[Ref]

Nervous system

• Frequency not reported: Paresthesias, loss of taste, taste perversion, headache, drowsiness, neuritis, vertigo, encephalopathy, numbness or tingling of fingers, toes, or face, cerebral angiitis^[Ref]

Other

• Frequency not reported: Fever^[Ref]

Ocular

• Frequency not reported: Sore, red, watery eyes (recurrent keratitis, conjunctival disorders)^[Ref]

Renal

• Frequency not reported: Acute glomerulonephritis, nephritis, glomerulonephritis^[Ref]

Respiratory

• Frequency not reported: Interstitial pneumonitis, alveolar/pulmonary hemorrhage^[Ref]

See also:

Frequently asked questions

• How does propylthiouracil work?

Further information

Propylthiouracil side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer