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Propylthiouracil Side Effects

Medically reviewed by Last updated on Mar 8, 2022.

For the Consumer

Applies to propylthiouracil: oral tablet


Oral route (Tablet)

Severe liver injury and acute liver failure, including fatalities, have been reported with propylthiouracil. Liver transplantation was required in some cases. Reserve propylthiouracil for patients who can not tolerate methimazole when radioactive iodine therapy or surgery are not appropriate treatment options. Propylthiouracil may be the preferred treatment when an antithyroid drug is indicated during or just prior to the first trimester of pregnancy, because of the risk of fetal abnormalities associated with methimazole.

Side effects requiring immediate medical attention

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:

More common

  • Black, tarry stools
  • chest pain
  • chills
  • cough
  • fever
  • painful or difficult urination
  • shortness of breath
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • swollen glands
  • unusual bleeding or bruising
  • unusual tiredness or weakness

Less common

  • Dark-colored urine
  • general feeling of discomfort, illness, or weakness
  • headache
  • light-colored stools
  • nausea or vomiting
  • stomach pain, continuing
  • upper right abdominal or stomach pain
  • yellow eyes and skin

Incidence not known

  • Abdominal or stomach pain
  • agitation
  • bleeding gums
  • bleeding under the skin
  • blood in the urine or stools
  • bloody or cloudy urine
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • coma
  • confusion
  • cough or hoarseness
  • cracks in the skin
  • decreased urine output
  • depression
  • difficulty with breathing
  • difficulty with moving
  • dizziness
  • drowsiness
  • feeling of fullness
  • fever with or without chills
  • general feeling of discomfort, illness, or weakness
  • high blood pressure
  • hostility
  • irritability
  • joint pain
  • lethargy
  • loss of appetite and weight
  • loss of heat from the body
  • lower back or side pain
  • muscle aching or cramping
  • muscle pain or stiffness
  • muscle twitching
  • numbness or tingling of the hands, feet, or face
  • pain in the ankles or knees
  • painful, red lumps under the skin, mostly on the legs
  • pinpoint red spots on the skin
  • rapid weight gain
  • red, swollen skin
  • redness, soreness, or itching skin
  • scaly skin
  • seizures
  • soreness of the muscles
  • sores on the skin
  • sores, ulcers, or white spots on the lips or in the mouth
  • sores, welting, or blisters
  • stupor
  • swelling of the face, ankles, hands, feet, or lower legs
  • swollen joints
  • swollen salivary glands
  • swollen, painful, or tender lymph glands in the neck, armpit, or groin
  • tightness in the chest
  • unusual weight gain
  • wheezing

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

Side effects not requiring immediate medical attention

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:

Incidence not known

  • Abnormal loss of hair
  • change in taste or bad unusual or unpleasant (after) taste
  • dizziness or lightheadedness
  • feeling of constant movement of self or surroundings
  • heartburn
  • hives or welts
  • loss of taste
  • pain or discomfort in the chest, upper stomach, or throat
  • sensation of spinning
  • skin rash
  • sleepiness

For Healthcare Professionals

Applies to propylthiouracil: oral tablet


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


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]


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]


Rare (Less than 0.1%): Agranulocytosis, thrombocytopenia, leucopenia, aplastic anemia, pancytopenia, hemorrhage, granulocytopenia

Frequency not reported: Hypoprothrombinemia, lymphadenopathy[Ref]


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]


Rare (Less than 0.1%): Vomiting

Frequency not reported: Nausea, vomiting, epigastric distress[Ref]


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


Frequency not reported: Edema[Ref]


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]


Frequency not reported: Fever[Ref]


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


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


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

Frequently asked questions


1. "Product Information. Propylthiouracil (propylthiouracil)." Lederle Laboratories (2001):

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

3. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online." (2006):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.