Adult: As treatment of hyperthyroidism in patients with Graves' disease or toxic multinodular goitre, and to ameliorate hyperthyroidism symptoms in preparation for radioactive iodine therapy or thyroidectomy: Usual dose: Initially, 300-600 mg daily, depending on the severity of the condition. For severe cases and/or very large goitres: Initially, 600-1,200 mg daily may be required. Doses are usually given in 3 divided doses at 8-hour intervals. When the patient becomes euthyroid, gradually reduce to a maintenance dose of 50-150 mg daily. Dosage and treatment recommendations may vary among countries and between individual products (refer to specific product guidelines). Child: When alternative therapies are inappropriate: 6-10 years 50-150 mg daily; >10 years 150-300 mg daily. All doses are divided every 8 hours. Individualise maintenance doses based on patient response. Dosage and treatment recommendations may vary among countries and between individual products (refer to specific product guidelines).
Oral Thyrotoxic crisis
Adult: In combination with other appropriate agents such as iodine, adrenergic blocking agents, and general supportive measures: 200 mg every 4-6 hours for the 1st 24 hours. May gradually reduce to a maintenance dose once full symptomatic control is achieved. Dosage and treatment recommendations may vary among countries and between individual products (refer to specific product guidelines).
What are the brands available for Propylthiouracil in Singapore?
Propyl
Propylthiouracil Teva
Renal Impairment
eGFR (mL/min/1.73 m2)
Dosage
<10
Reduce dose by 50%.
10-50
Reduce dose by 25%.
Dosage and treatment recommendations may vary among countries and between individual products (refer to specific product guidelines).
Hepatic Impairment
Dosage reduction may be needed.
Administration
Propylthiouracil Should be taken with food.
Special Precautions
Patient with risk factors for bone marrow suppression or concomitantly receiving agents that are known to cause myelosuppression (particularly agranulocytosis). Withdraw propylthiouracil before irradiation or treatment with radioiodine (refer to specific product guideline for detailed information). Renal and hepatic impairment. Neonates, children (use is not recommended except in cases when alternative therapies are inappropriate); elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Bleeding, hypoprothrombinaemia, bone marrow suppression (e.g. aplastic anaemia, thrombocytopenia, leucopenia), exfoliative dermatitis, unexplained fever, hypothyroidism, lupus-like syndrome (e.g. splenomegaly), nephritis, interstitial pneumonitis. Blood and lymphatic system disorders: Lymphadenopathy. Ear and labyrinth disorders: Vertigo. Gastrointestinal disorders: Nausea, vomiting, epigastric distress, ageusia, dysgeusia. General disorders and administration site conditions: Oedema. Hepatobiliary disorders: Hepatitis, jaundice. Immune system disorders: Hypersensitivity reactions. Musculoskeletal and connective tissue disorders: Arthralgia, myalgia. Nervous system disorders: Drowsiness, neuritis, paraesthesia, headache. Skin and subcutaneous tissue disorders: Rash, urticaria, pruritus, alopecia, skin pigmentation. Potentially Fatal: Liver injury leading to liver failure or liver transplantation; agranulocytosis; vasculitis (including alveolar or pulmonary haemorrhage, cerebral angiitis, glomerulonephritis, ischaemic colitis, and leucocytoclastic cutaneous vasculitis).
Monitor CBC with differential (baseline and if febrile illness or pharyngitis occurs); LFTs, including bilirubin, alkaline phosphatase, ALT, and AST (baseline and if liver injury symptoms occur); prothrombin time (during treatment, especially prior to surgical procedures); thyroid function tests, including TSH and free thyroxine (T4) concentrations (periodically during therapy). Assess for signs and symptoms of liver injury (e.g. fatigue, weakness, vague abdominal pain, loss of appetite, itching, easy bruising, yellowing of the eyes or skin), especially during the 1st 6 months of therapy; agranulocytosis (e.g. fever, mouth ulcers, rashes, sore throat, chills, malaise).
Management: Symptomatic and supportive treatment. Perform gastric lavage or emesis to empty the stomach. Activated charcoal may also be administered. May give antibiotics and corticosteroids, or transfuse fresh whole blood if bone marrow depression develops. Prothrombin deficiency may be controlled by phytomenadione.
Drug Interactions
May increase the activity of oral anticoagulants (e.g. warfarin) due to anti-vitamin K properties of propylthiouracil. Concomitant use with agents that are known to cause myelosuppression may potentiate the risk of agranulocytosis. May increase the serum levels of digitalis glycosides (e.g. digoxin) and theophylline once hyperthyroidism is corrected.
Action
Description: Overview: Propylthiouracil is a thiourea derivative antithyroid agent. Mechanism of Action: Propylthiouracil inhibits thyroid hormone biosynthesis by blocking thyroid peroxidase. This interferes with the oxidation of iodide ion and iodotyrosyl groups, inhibits the incorporation of iodine into tyrosyl residues of thyroglobulin, and prevents the coupling of iodotyrosyl residues to form iodothyronine. In addition, propylthiouracil inhibits the peripheral conversion of thyroxine (T4) to triiodothyronine (T3) and acts as a thyroid blocker by decreasing the retention of radioactive iodine (I-131) within the thyroid gland. Pharmacodynamics: Propylthiouracil causes depletion of thyroglobulin and a reduction in circulating thyroid hormone levels. However, it does not inhibit the action or release of thyroid hormones that have already been formed or are present in the thyroid gland, nor does it affect the activity of exogenously administered thyroid hormones. In patients with Graves' disease, propylthiouracil may also gradually reduce the levels of circulating thyroid-stimulating immunoglobulins. Onset: 24-36 hours. Duration: 12-24 hours. Pharmacokinetics: Absorption: Rapidly absorbed from the gastrointestinal tract. Bioavailability: 50-75%. Time to peak plasma concentration: 1-2 hours. Distribution: Concentrated in the thyroid gland. Crosses the placenta and enters breast milk. Plasma protein binding: 80-85%. Metabolism: Extensively metabolised in the liver into its glucuronic acid conjugate. Excretion: Via urine (35%; primarily as metabolites). Elimination half-life: 1-2 hours.
Chemical Structure
Propylthiouracil Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 657298, Propylthiouracil. https://pubchem.ncbi.nlm.nih.gov/compound/Propylthiouracil. Accessed Oct. 27, 2025.
Storage
Store between 15-30°C. Follow applicable procedures for receiving, handling, administration, and disposal.
H03BA02 - propylthiouracil ; Belongs to the class of thiouracils. Used in the management of thyroid diseases.
References
Brayfield A, Cadart C (eds). Propylthiouracil. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 06/10/2025.Joint Formulary Committee. Propylthiouracil. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 06/10/2025.Paediatric Formulary Committee. Propylthiouracil. BNF for Children [online]. London. BMJ Group, Pharmaceutical Press, and RCPCH Publications. https://www.medicinescomplete.com. Accessed 06/10/2025.Propyl Tablet (Imeks Pharma Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 06/10/2025.Propylthiouracil 100 mg Tablets (Macleods Pharma UK Limited). MHRA. https://products.mhra.gov.uk. Accessed 06/10/2025.Propylthiouracil 50 mg Tablets (Morningside Healthcare Ltd). MHRA. https://products.mhra.gov.uk. Accessed 06/10/2025.Propylthiouracil Tablet (Actavis Pharma, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 06/10/2025.Propylthiouracil, PTU. Gold Standard Drug Database in ClinicalKey [online]. Elsevier Inc. https://www.clinicalkey.com. Accessed 15/10/2025.Propylthiouracil. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 06/10/2025.Propylthiouracil. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 06/10/2025.Propylthiouracil. UpToDate Lexidrug, Pediatric and Neonatal Lexi-Drugs Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 15/10/2025.
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