Minor adverse effects of propylthiouracil include: rash, urticaria, pruritus, abnormal hair loss, skin pigmentation, oedema, nausea, vomiting, epigastric distress, loss of taste, arthralgia, myalgia, paresthesia and headache.
Leucopenia is a common adverse effect, but it is usually mild and reversible.
Agranulocytosis is the most serious adverse effect of propylthiouracil, but the incidence is very low. It tends to occur within the first two months of therapy and patients over the age of 40 years and receiving larger doses are at greater risk.
Frequency unknown: Hepatitis, Hepatic Failure
Other severe, but infrequent adverse events include: aplastic anaemia; drug fever; lupus-like syndrome; severe hepatic reactions (including encephalopathy, fulminant hepatic necrosis and death); periarteritis; hypoprothrombinaemia; thrombocytopenia and bleeding.
Nephritis, interstitial pneumonitis, cutaneous and systemic vasculitis and polymyositis have also been reported. Hypersensitivity reactions may be associated with the development of anti-neutrophil cytoplasmic antibodies (ANCA).
Propylthiouracil-induced hepatoxicity is rare and usually manifests as hepatocellular hepatitis with or without jaundice. Cholestatic jaundice has also occurred. Adverse liver effects are generally reversible on cessation of propylthiouracil.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme on the MHRA website www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.