Propylthiouracil (PTU)

Source: UK SPC (eMC) for Propylthiouracil 100mg Tablets, §4.2 (https://www.medicines.org.uk/emc/product/14253/smpc). OTHER INDICATIONS — Preparation for surgery: as for management of hyperthyroidism, until the patient becomes euthyroid. Adjunct to radioactive iodine therapy: as for management of hyperthyroidism, for several weeks prior to radio-iodine treatment; withdraw propylthiouracil 2 to 4 days before irradiation, and note the radio-iodine dose may need adjusting because propylthiouracil may have a radioprotective effect. THYROTOXIC CRISIS: 200 mg every 4 to 6 hours for the first 24 hours, decreasing the dose as the crisis subsides. ELDERLY: the adult dose applies, but caution is advised in the presence of renal or hepatic impairment, where a dose reduction may be justified. PAEDIATRIC (given in the SPC but not as a single clean per-kg figure, hence paedDose is null — verify all of this against a children's formulary before use): juvenile hyperthyroidism — children aged 6–10 years, initial dose 50–150 mg daily; children over 10 years, initial dose 150–300 mg (or 150 mg/m2) daily; maintenance dose is determined by the patient's response. Treatment of hyperthyroidism in neonates: 5–10 mg/kg daily. 'No other specific children's doses are known.' MONITORING/SAFETY from §4.4: warn patients that fever, mouth ulcers, rashes or sore throat may indicate agranulocytosis — they should contact their doctor immediately and treatment should be stopped; perform a full blood count if there is clinical evidence of infection; use with extreme caution with other drugs known to cause agranulocytosis; use with caution in patients over 40 years old; propylthiouracil may cause hypoprothrombinaemia and bleeding, so monitor prothrombin time during therapy, especially before surgery; discontinue if clinically important abnormal liver function occurs (severe hepatic reactions including fatal cases and cases requiring liver transplant have been reported in adults and children, mostly within 6 months); prolonged therapy and/or excessive doses may cause hypothyroidism, so monitor thyroid function regularly; systemic vasculitis can occur at any time up to several years after starting and the risk may increase with prolonged use — discontinue promptly. Contains lactose — not for patients with rare hereditary galactose intolerance, total lactase deficiency or glucose-galactose malabsorption. METHOD: administered by the oral route.