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propylthiouracil (PTU)

Alias: PTU. Indications: 1) palliative treatment of hyperthyroidism & thyrotoxicosis 2) adjunct to ameliorate hyperthyroidism in preparation for surgical treatment 3) use PTU only in patients who have an allergy or intolerance to methimazole, or in pregnant women in their first trimester [3] Contraindications: - liver failure - discontinue PTU if liver damage is suspected Dosage: 1) start 100 mg PO TID, then adjust 2) decrease over several weeks to 50-150 mg/day 3) thyroid storm: 200-250 mg every 6 hours until euthyroid Tabs: 50 mg. Monitor: - monitor patients on PTU for signs of liver damage, particularly during the first 6 months of therapy; liver function testing - prothrombin time every 3 months - thyroid function every 3 months a) serum TSH b) serum T4 &/or serum free T4 - CBC if fever or pharyngitis to rule out agranulocytosis Adverse effects: 1) common (> 10%) a) skin rash b) leukopenia c) fever 2) less common (1-10%) - dizziness, nausea/vomiting, stomach pain, loss of taste, agranulocytosis, SLE-like syndrome 3) uncommon (< 1%) - thrombocytopenia, aplastic anemia, swollen salivary glands, cholestatic jaundice, nephrotic syndrome, constipation, goiter, weight gain, edema, paresthesia, drowsiness, vertigo, headache, rash, urticaria, pruritus, hair loss, arthralgia 4) other - serious liver injury, including liver failure & death [3] - hepatotoxicity > that of methimazole [4] Test interactions: - interferes with thyroid scan, stop 1 week prior to scan Drug interactions: (see methimazole) Mechanism of action: 1) inhibits synthesis of thyroid hormones by interfering with the incorporation of iodine into tyrosyl residues of thyroglobulin 2) inhibits coupling of iodotyrosyl residues to form iodothyronine 3) inhibits peripheral conversion of T4 to T3

Interactions

drug adverse effects of antithyroid agent(s) monitor with antithyroid agents

Related

methimazole; thiamazole (Tapazole)

General

antithyroid agent

Properties

MISC-INFO: elimination route LIVER pregnancy-category D safety in lactation -

Database Correlations

PUBCHEM correlations

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  2. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  3. FDA MedWatch Propylthiouracil 06/04/2009, updated 04/21/2010 http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm164162.htm - FDA Drug Safety Communication: New Boxed Warning on severe liver injury with propylthiouracil, 04-21-2010 http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm209023.htm - Prescriber's Letter 17(6): 2010 New Boxed Warning on Severe Liver Injury with Propylthiouracil Detail-Document#: 260605 (subscription needed) http://www.prescribersletter.com
  4. Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  5. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998