From the FDA Drug Label
WARNING Severe liver injury and acute liver failure, in some cases fatal, have been reported in patients treated with propylthiouracil. Propylthiouracil can cause serious side effects, including: Severe liver problems. In some cases, liver problems can happen in people who take Propylthiouracil including: liver failure, the need for liver transplant, or death
Propylthiouracil and Liver Disease: Propylthiouracil can cause severe liver injury and acute liver failure, which can be fatal. Patients taking propylthiouracil should be monitored for symptoms of liver problems, including:
- Fever
- Loss of appetite
- Nausea
- Vomiting
- Tiredness
- Itchiness
- Pain or tenderness in the right upper stomach area
- Dark urine
- Pale or light-colored bowel movements
- Yellowing of the skin or eyes If these symptoms occur, patients should stop taking propylthiouracil and call their doctor right away 1, 1.
From the Research
Propylthiouracil (PTU) should be avoided in patients with liver disease due to its potential to cause serious hepatotoxicity, and its use is not supported by recent high-quality evidence for the treatment of alcoholic liver disease. The most recent and highest quality study, a systematic review from 2005 2, found no significant effects of propylthiouracil on mortality, liver-related mortality, complications of the liver disease, or liver histology in patients with alcoholic liver disease. Additionally, propylthiouracil was associated with a non-significant increased risk of non-serious adverse events and with the seldom occurrence of serious adverse events, such as leukopenia.
Key Considerations
- PTU is associated with a higher risk of severe liver injury compared to other antithyroid medications like methimazole, particularly in adults 3.
- If a patient with pre-existing liver disease requires treatment for hyperthyroidism, methimazole is generally preferred as first-line therapy unless specifically contraindicated.
- Frequent liver function monitoring is essential for patients who must use PTU, typically every 2-4 weeks.
- Signs of liver injury include jaundice, dark urine, right upper quadrant pain, fatigue, anorexia, pruritus, or unexplained symptoms.
- PTU-induced liver damage can range from mild transaminase elevations to fulminant hepatic failure requiring transplantation.
Monitoring and Management
- Liver function tests should be monitored closely in patients taking PTU, and the medication should be discontinued immediately if liver function tests become significantly abnormal (typically ALT >3 times upper limit of normal) or symptoms of liver injury develop.
- Alternative treatments for hyperthyroidism, such as radioactive iodine therapy or thyroidectomy, should be considered after stabilization.
- The mechanism of PTU-induced liver damage involves direct hepatocellular injury and immunoallergic reactions, highlighting the importance of careful monitoring and prompt discontinuation of the medication if necessary.