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MEDICINE MONOGRAPH CODE: [6.3] ID: TIP-MED-000093

Propylthiouracil (PTU)

Active Ingredient / Scientific Identity: Propylthiouracil • Class: Thioamide Antithyroid Agent (Inhibits Thyroid Peroxidase AND Peripheral Type-1 5'-Deiodinase Conversion of T4 to T3)

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THE INDIAN PHARMACIST — Educational Reference Sheet
Profile: Propylthiouracil (PTU) ([6.3] | ID: TIP-MED-000093) • Last Reviewed: 2026-11-10
Source URL: https://theindianpharmacist.com/medicine/6-3-propylthiouracil-ptu/
Generic / Entity NamePropylthiouracil (PTU) ([6.3])
Verified Indian Brands / RefGeneric Compendial Entry (No Commercial Brand Claimed)
Pharmacological ClassThioamide Antithyroid Agent (Inhibits Thyroid Peroxidase AND Peripheral Type-1 5'-Deiodina
Available Dosage FormsOral Uncoated Tablets: 50 mg
Regulatory ClassificationSchedule H & Schedule G Prescription Drug ('Caution: It is dangerous to take this pre
Key Warning & Review DateRenal: Monitor closely in severe CKD. Hepatic: Contraindicated in active liver disease; discontinue immediately if transamina
Reviewed: 2026-11-10
Safety Matrix:⚖️ Legal Status: Schedule H & Schedule G Prescription Drug ('Caution:✔️ Standard Clinical Dispensing Precautions

1. Clinical & Scientific Overview

Propylthiouracil (PTU) (TIP-MED-000093, Reference Code [6.3]) is classified under Thyroid, Pituitary, Adrenal & Hormonal Medicines (Ch 06) as a Thioamide Antithyroid Agent (Inhibits Thyroid Peroxidase AND Peripheral Type-1 5'-Deiodinase Conversion of T4 to T3). Within the Indian regulatory and compendial framework, it is governed under Schedule H & Schedule G Prescription Drug ('Caution: It is dangerous to take this preparation except under medical supervision' — Drugs Rules 1945).

Verified Indian Market Examples / Compendial Status:
Representative Indian Market Examples (Edition 2.7 Ch 06 [6.3], p. 73): PTU (Macleods), Propylthiouracil tablets (50 mg) — Strengths & Dosage Forms: Oral Uncoated Tablets: 50 mg
Representative Indian Market Examples (Edition 2.7 Ch 06 [6.3], p. 73): PTU (Macleods), Propylthiouracil tablets (50 mg) — Strengths & Dosage Forms: Oral Uncoated Tablets: 50 mg
Dosage Forms & Available Strengths:
Oral Uncoated Tablets: 50 mg
Routes: Oral / Parenteral / Topical as specified by formulation

3. Mechanism of Action & Pharmacodynamics

Thioamide Antithyroid Agent (Inhibits Thyroid Peroxidase AND Peripheral Type-1 5'-Deiodinase Conversion of T4 to T3) acting on target receptor/enzyme pathways in Thyroid, Pituitary, Adrenal & Hormonal Medicines (Ch 06): clinical efficacy is mediated via Thioamide Antithyroid Agent (Inhibits Thyroid Peroxidase AND Peripheral Type-1 5'-Deiodinase Conversion of T4 to T3) for Hyperthyroidism during the first trimester of pregnancy (preferred over carbimazole in weeks 1–13 to avoid carbimazole embryopathy); Thyroid Storm / Thyrotoxic Crisis (because high-dose PTU uniquely blocks peripheral conversion of T4 to active T3); patients intolerant to carbimazole (non-agranulocytosis mild rash) who decline radioiodine or surgery..

4. Therapeutic Indications & Evidence-Supported Uses

  • Hyperthyroidism during the first trimester of pregnancy (preferred over carbimazole in weeks 1–13 to avoid carbimazole embryopathy)
  • Thyroid Storm / Thyrotoxic Crisis (because high-dose PTU uniquely blocks peripheral conversion of T4 to active T3)
  • patients intolerant to carbimazole (non-agranulocytosis mild rash) who decline radioiodine or surgery

🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.

5. Educational Dosage Context, Formulations & Administration

Educational Dosing & Regimen Summary: General Adult Reference: Initially 100 mg to 300 mg daily in 3 divided doses (every 8 hours); maintenance 50 mg to 150 mg daily in 2–3 divided doses. (Thyroid Storm: 500–1000 mg loading, then 250 mg every 4 hours in ICU). Follow endocrinologist prescription.

Administration & Meal Timing: Take with or after meals at consistent 8-hour intervals. | Three times daily (every 8 hours: morning, afternoon, night) due to short plasma half-life (1–2 hours).

6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment

Absorption & Disposition:
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Metabolism & Biotransformation:
Renal: Monitor closely in severe CKD. Hepatic: Contraindicated in active liver disease; discontinue immediately if transaminases rise >3x ULN or jaundice develops.
Elimination & Renal Adjustment:
Renal: Monitor closely in severe CKD. Hepatic: Contraindicated in active liver disease; discontinue immediately if transaminases rise >3x ULN or jaundice develops.
Hepatic Impairment Considerations:
Renal: Monitor closely in severe CKD. Hepatic: Contraindicated in active liver disease; discontinue immediately if transaminases rise >3x ULN or jaundice develops.

7. Contraindications, Precautions & High-Risk Warnings

Contraindications & Red-Flag Precautions:
  • Boxed Warning for Severe Hepatotoxicity: PTU carries a significantly higher risk of acute fulminant hepatic failure than carbimazole (hence it is NOT first-line for routine adult or paediatric hyperthyroidism outside the 1st trimester or thyroid storm). Cross-reactivity (~50%) exists with carbimazole for agranulocytosis—never switch to PTU if a patient developed agranulocytosis on carbimazole!

Key Clinical Precautions: Renal: Monitor closely in severe CKD. Hepatic: Contraindicated in active liver disease; discontinue immediately if transaminases rise >3x ULN or jaundice develops.

8. Adverse Effects Profile

Common & Mechanism-Related Adverse Effects:
  • Nausea, epigastric distress, pruritic skin rash, arthralgia, dysgeusia (loss of taste), transient leukopenia.
  • Fulminant hepatic necrosis and acute liver failure, agranulocytosis (fever, severe pharyngitis, stomatitis), ANCA-associated vasculitis (lupus-like syndrome, glomerulonephritis, alveolar haemorrhage), thrombocytopenia.
Serious / Dose-Limiting Adverse Effects:
  • Monitor for severe hypersensitivity, organ toxicity, or dose-limiting adverse events.

9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions

  • Potentiates oral anticoagulants (warfarin); restoring euthyroid state increases serum levels of digoxin, beta-blockers, and theophylline

10. Clinical Monitoring, Patient Counselling & Storage

Clinical & Laboratory Monitoring: Monitor clinical response, baseline renal/hepatic parameters, and relevant serum biomarkers.

Pharmacist Patient Counselling Points:

  • Patient Counselling Checklist: Deliver a dual red-flag warning: (1) Stop PTU and get an urgent blood count (CBC) if sore throat, mouth sores, or fever develop; (2) Stop PTU and report immediately if anorexia, right upper abdominal pain, dark tea-coloured urine, or yellow eyes (jaundice) appear. Emphasise 8-hourly adherence.
  • Meal & Clock Timing Instruction: Take with or after meals at consistent 8-hour intervals. (Three times daily (every 8 hours: morning, afternoon, night) due to short plasma half-life (1–2 hours).)
  • Missed Dose Protocol: Take as soon as remembered unless within 2–3 hours of the next scheduled dose.
  • Geriatric Dispensing Pearl: Rarely used for routine chronic therapy in the elderly unless intolerant to carbimazole or during acute thyrotoxic crisis; monitor LFTs and WBC counts vigilantly.

Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Oral Uncoated Tablets: 50 mg

11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)

THE 12-STEP ORAL DRUG JOURNEY THROUGH THE HUMAN BODY (LADME) Note: IV bolus enters Step 6 directly (F = 100%); Sublingual & Transdermal routes bypass Step 4–5 Portal First-Pass Metabolism 1. Oral Administration • Tablet / Capsule swallowed • Gastric emptying to duodenum pH 1.5–3.5 (Stomach) 2. Disintegration & Dissolution • Tablet breaks into granules • API dissolves in GI fluid Noyes-Whitney Dissolution Rate 3. GI Epithelial Absorption • Crosses intestinal villi • Passive / Active / P-gp efflux Small Intestine (Large Surface Area) 4. Portal Circulation • Mesenteric veins → Portal vein • Delivers blood to liver sinusoids Pre-systemic Venous Conduit 5. First-Pass Metabolism • Gut & hepatic CYP450 extraction • High: GTN, Propranolol, Morphine Determines Bioavailability (F = f_a × (1-E_H)) 6. Systemic Circulation • Hepatic vein → IVC → Heart • Unbound vs Albumin-bound drug Only FREE drug is active 7–8. Tissue Distribution (Vd) • Capillary permeation to organs • Blood-Brain & Placental barriers Vd = Dose / C_0 (L or L/kg) 9. Target Site of Action • Receptors (GPCR, Ion channel) • Enzymes & Carrier Transporters Pharmacodynamic Effect (E_max, EC50) 10. Hepatic Biotransformation • Phase I (CYP450 Oxidation/Hydrolysis) • Phase II (Glucuronidation/Sulfation) Converts lipophilic drug → hydrophilic metabolite 11. Renal & Biliary Elimination • Nephron: Filtration + Secretion − Reabsorption • Biliary excretion & Enterohepatic recycling Total Clearance CL_tot = CL_renal + CL_hepatic 12. Excretion from the Body • Urine (Primary polar metabolite route) • Bile/Faeces, Expired Air, Sweat, Milk Elimination Half-Life t1/2 = (0.693 × Vd) / CL
svg-v339-01-adme-12-step-journey — 8.1 Complete 12-Step Journey of an Orally Administered Drug (ADME): Figure 8.1: The 12-step physiological journey of a typical orally administered solid dosage form through Liberation, Absorption, Distribution, Metabolism, and Excretion (LADME). Note: Parenteral (IV), sublingual, and inhalational routes bypass gastrointestinal absorption and/or hepatic first-pass metabolism.

12. Authoritative References, Regulatory Sources & Editorial Disclaimer

Primary Compendial & Guideline Reference: Indian Pharmacist Desk Reference — Professional Edition 2.7 (2026–27) • Ch 06 [6.3] (p. 73)

Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)

Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: HANDBOOK_SOURCE_CONTENT

Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.

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Educational Reference Notice: This printout from THE INDIAN PHARMACIST (https://theindianpharmacist.com/medicine/6-3-propylthiouracil-ptu/, Last Reviewed: 2026-11-10) is an educational reference sheet for students and healthcare learners. It is NOT an official prescribing guideline or patient-specific treatment order.