propylthiouracil (PTU)
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Introduction
Alias: PTU.
Indications
- palliative treatment of hyperthyroidism & thyrotoxicosis
- adjunct to ameliorate hyperthyroidism in preparation for surgical treatment
- 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
- start 100 mg PO TID, then adjust
- decrease over several weeks to 50-150 mg/day
- 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
- CBC if fever or pharyngitis to rule out agranulocytosis
Adverse effects
- common (> 10%)
- less common (1-10%)
- dizziness, nausea/vomiting, stomach pain, loss of taste, agranulocytosis, SLE-like syndrome
- uncommon (< 1%)
- other
- serious liver injury, including liver failure & death[3]
- hepatotoxicity > that of methimazole[4]
Drug interactions
(see methimazole)
Test interactions
- interferes with thyroid scan, stop 1 week prior to scan
Mechanism of action
- inhibits synthesis of thyroid hormones by interfering with the incorporation of iodine into tyrosyl residues of thyroglobulin
- inhibits coupling of iodotyrosyl residues to form iodothyronine
- inhibits peripheral conversion of T4 to T3
More general terms
Additional terms
References
- ↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ 3.0 3.1 3.2 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#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=260605&pb=PRL (subscription needed) http://www.prescribersletter.com - ↑ 4.0 4.1 Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
- ↑ Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998