Propylthiouracil Side Effects

It is possible that some side effects of propylthiouracil may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to propylthiouracil: oral tablet

As well as its needed effects, propylthiouracil may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking propylthiouracil, check with your doctor immediately:

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

If any of the following symptoms of overdose occur while taking propylthiouracil, get emergency help immediately:

Symptoms of overdose
  • Bloody, black, or tarry stools
  • high fever
  • itching skin
  • pale skin
  • swelling

Some propylthiouracil side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned 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


In general the overall incidence of side effects is relatively low (1% to 5%). Serious side effects may occur. These have included agranulocytosis, hepatitis, and vasculitis.


Hematologic side effects have included agranulocytosis (0.5%), granulocytopenia, and thrombocytopenia, as well as rare reports of aplastic anemia. Transient leukopenia is reported in up to 12% of patients, although this may occur in untreated hyperthyroid patients as well. Hypoprothrombinemia and bleeding have been reported.

Agranulocytosis occurs in approximately 0.5% of patients treated with propylthiouracil. Onset is typically within the first three months of therapy but isolated cases have occurred much later. Risk may be greater in patients over 40 years of age and in females.

Rare cases of aplastic anemia are also reported, although recovery in these cases is relatively high (73%).


Hepatic side effects have included hepatocellular hepatitis with or without jaundice, cholestatic jaundice, hepatic encephalopathy, fulminant hepatic necrosis, splenomegaly, and elevations in liver function tests. Fatal hepatitis has been reported.

Propylthiouracil-induced hepatotoxicity occurs rarely, although the exact incidence is unknown. Most cases present as hepatocellular hepatitis, with or without jaundice. Cholestatic jaundice is also reported. While many cases resolve with discontinuation of propylthiouracil therapy and supportive care, fatalities have occurred despite aggressive therapy.

While severe hepatotoxicity appears to be rare, transient and asymptomatic elevations in transaminases may occur in up to 28% of patients.


Dermatologic side effects have included rash, urticaria, hair loss, and skin pigmentation. Exfoliative dermatitis and erythema nodosum have also been reported. Cases of cutaneous vasculitis resulting in death have been reported.

Erythema nodosum and fatal cases of cutaneous vasculitis are reported with propylthiouracil. In addition, purpuric rash, maculopapular rash, or bullous hemorrhagic lesions may occur in conjunction with other adverse effects of propylthiouracil such as hepatotoxicity or hematologic toxicity.


Antineutrophil cytoplasmic antibodies against human neutrophil elastase as well as against proteinase 3 and/or myeloperoxidase were documented in six patients who developed vasculitis during propylthiouracil therapy for hyperthyroidism.

Clinical improvement and disappearance of or decline in antibodies were noted upon discontinuation of propylthiouracil in all six patients. Such antibodies were absent in seven other patients who did not develop vasculitis during propylthiouracil therapy for hyperthyroidism.

Immunologic side effects have included hepatic, hematologic, respiratory, and dermatologic effects. Vasculitis has been associated with propylthiouracil therapy as have positive ANA titers and a lupus-like syndrome.


Respiratory side effects have included two cases of interstitial pneumonitis. Pulmonary infiltrates or alveolar hemorrhage have also been reported.

Manifestations of a vasculitic syndrome with the presence of anti-neutrophilic cytoplasmic antibodies (ANCA) have included alveolar hemorrhage or pulmonary infiltrates.

Nervous system

Nervous system side effects have included paresthesia, headache, drowsiness, neuritis, and vertigo.


Renal side effects have rarely included acute interstitial nephritis and renal failure.

Manifestations of a vasculitic syndrome with the presence of anti-neutrophilic cytoplasmic antibodies (ANCA) have included rapidly progressing glomerulonephritis (crescentic and pauci-immune necrotizing glomerulonephritis) sometimes leading to acute renal failure.


Cardiovascular side effects have included a case report of superior vena cava syndrome.


Gastrointestinal side effects have included nausea, vomiting, epigastric distress, and taste disturbances.


Musculoskeletal side effects have included arthralgia, myalgia, frank arthritis, and polymyositis.


Metabolic side effects have included a case report of severe hypocalcemia.


Other side effects have included tinnitus, reversible sensorineural hearing loss, sialadenopathy, lymphadenopathy, and fever.

Reversible sensorineural hearing loss characterized by tinnitus and impaired hearing is reported in at least two cases. Fatigue, weight loss, and lupus-like syndrome accompanied the hearing loss in one case. In the other, migratory polyarthritis, fever, chills, and nonproductive cough were noted. Symptoms resolved after discontinuation of propylthiouracil.

Manifestations of a vasculitic syndrome with the presence of anti-neutrophilic cytoplasmic antibodies (ANCA) have included fever and leukocytoclastic vasculitis.

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