INN monograph
Propylthiouracil
Thyroid Hormone Synthesis Inhibitor [EPC] · POM
Verified · Updated 01 Aug 2026 · Source: Local active-ingredient clinical extract; FDA drug label via OpenFDA/DailyMed; Professional class pharmacology (Therapeutic agent (verify pharmacological class))
Kenya market
Wholesale / list prices where loaded
Risk first
Contraindications
- Hypersensitivity to the active substance or excipients.
- Additional absolute contraindications are indication- and product-specific — consult SmPC.
Precautions
- WARNINGS Liver Toxicity Liver injury resulting in liver failure, liver transplantation, or death, has been reported with propylthiouracil therapy in adult and pediatric patients.
- No cases of liver failure have been reported with the use of methimazole in pediatric patients.
- For this reason, propylthiouracil is not recommended for pediatric patients except when methimazole is not well-tolerated and surgery or radioactive iodine therapy are not appropriate therapies.
- Biochemical monitoring of liver function (bilirubin, alkaline phosphatase) and hepatocellular integrity (ALT, AST) is not expected to attenuate the risk of severe liver injury due to its rapid and unpredictable onset.
- Patients should be informed of the risk of liver failure.
- Patients should be instructed to report any symptoms of hepatic dysfunction (anorexia, pruritus, right upper quadrant pain, etc.), particularly in the first six months of therapy.
- When these symptoms occur, propylthiouracil should be discontinued immediately and liver function tests and ALT and AST levels obtained.
- Use in Pregnancy There are cases of liver injury, including liver failure and death, in women treated with propylthiouracil during pregnancy.
- Two reports of in utero exposure with liver failure and death of a newborn have been reported.
- If propylthiouracil is used during pregnancy, or if the patient becomes pregnant while taking propylthiouracil, the patient should be warned of the rare potential hazard to the mother and fetus of liver damage.
- Propylthiouracil crosses the placenta and can cause fetal goiter and cretinism when administered to a pregnant woman (see Precautions, Pregnancy ).
- After the first trimester of pregnancy, the use of an alternative antithyroid medication may be advisable (see Precautions, Pregnancy ).
Point of care
Dosing
Adult
DOSAGE AND ADMINISTRATION Propylthiouracil is administered orally. The total daily dosage is usually given in 3 equal doses at approximately 8-hour intervals. Adults The initial dose is 300 mg daily. In patients with severe hyperthyroidism, very large goiters, or both, the initial dose may be increased to 400 mg daily; an occasional patient will require 600 to 900 mg daily initially. The usual maintenance dose is 100 to 150 mg daily. Pediatric Patients Propylthiouracil is generally not recommended for use in the pediatric patient population except in rare instances in which other alternative therapies are not appropriate options. Studies evaluating appropriate dosing regimen have not been conducted in the pediatric population although general practice would suggest initiation of therapy in patients 6 years or older at a dosage of 50 mg daily with careful upward titration based on clinical response and evaluation of TSH and free T4 levels. Although cases of severe liver injury have been reported with doses as low as 50 mg/day, most cases were associated with doses of 300 mg/day and higher. Geriatric Patients Clinical studies of propylthiouracil did not include sufficient numbers of subjects aged 65 or over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
Paediatric
See label paediatric section if present; otherwise use paediatric formulary — do not extrapolate adult doses.
Renal
Review renal impairment dosing; many agents need CrCl/eGFR adjustment.
- CrCl 0–120: Confirm renal dosing in product SmPC / primary label.
Hepatic
Review hepatic impairment dosing; monitor LFTs if agent is hepatically cleared or hepatotoxic.
Safety
Drug interactions
- Professional use: confirm indication, dose, duration, monitoring and patient counselling points against current Kenya STG / EML and the product SmPC.
- Document allergy status and key interactions.
Safety
Adverse effects
- ADVERSE REACTIONS The following adverse reactions have been reported with the use of propylthiouracil.
- Because these events generally come from voluntary reporting from a population of uncertain size, it is not possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
- Severe adverse reactions include liver injury presenting as hepatitis, liver failure necessitating liver transplantation or resulting in death (see WARNINGS ).
- Inhibition of myelopoiesis (agranulocytosis, granulopenia, aplastic anemia, and thrombocytopenia), drug fever, a lupus-like syndrome (including splenomegaly and vasculitis), periarteritis, hypoprothrombinemia, and bleeding have been reported.
- Nephritis, glomerulonephritis, interstitial pneumonitis, exfoliative dermatitis, and erythema nodosum have also been reported.
- There are reports of a vasculitis associated with the presence of anti-neutrophilic cytoplasmic antibodies (ANCA), resulting in severe complications and death (see WARNINGS ).
- There have been rare reports of serious hypersensitivity reactions (e.g., Stevens Johnson syndrome and toxic epidermal necrolysis) in patients treated with propylthiouracil.
- Other adverse reactions include skin rash, uticaria, nausea, vomiting, epigastric distress, arthralgia, paresthesias, loss of taste, taste perversion, abnormal loss of hair, myalgia, headache, pruritus, drowsiness, neuritis, edema, vertigo, skin pigmentation, jaundice, sialadenopathy, and lymphadenopathy.
Use
Indications
INDICATIONS AND USAGE Propylthiouracil is indicated: in patients with Graves’ disease with hyperthyroidism or toxic multinodular goiter who are intolerant of methimazole and for whom surgery or radioactive iodine therapy is not an appropriate treatment option to ameliorate symptoms of hyperthyroidism in preparation for thyroidectomy or radioactive iodine therapy in patients who are intolerant of methimazole.
Pharmacology
Mode of action
It inhibits the synthesis of thyroid hormones by interfering with the incorpora- tion of iodine into tyrosyl residues of thyroglobulin.
Full mechanism text
It inhibits the synthesis of thyroid hormones by interfering with the incorpora- tion of iodine into tyrosyl residues of thyroglobulin. It also inhibits the coupling of these iodotyrosyl residues to form iodothyronine.
ADME
Pharmacokinetics & PD
| Onset | Product-specific |
|---|---|
| Duration | Product-specific |
| Route | See product SmPC |
Full PK/PD text
CLINICAL PHARMACOLOGY Propylthiouracil inhibits the synthesis of thyroid hormones and thus is effective in the treatment of hyperthyroidism. The drug does not inactivate existing thyroxine and triiodothyronine that are stored in the thyroid or circulating in the blood, nor does it interfere with the effectiveness of thyroid hormones given by mouth or by injection. Propylthiouracil inhibits the conversion of thyroxine to triiodothyronine in peripheral tissues and may therefore be an effective treatment for thyroid storm. Propylthiouracil is readily absorbed and is extensively metabolized. Approximately 35% of the drug is excreted in the urine, in intact and conjugated forms, within 24 hours.
Kenya
Brands & prices
| Brand | Company | Pack | KES |
|---|---|---|---|
| Propylthiouracil, by Metro | Distributed by Metro Pharmaceuticals Limited | Standard Commercial Pack | — |
Special populations
Pregnancy & lactation
Pregnancy
Use only if potential benefit justifies potential risk; prefer agents with better reproductive data when alternatives exist.
Lactation
Assess infant risk vs benefit of maternal therapy; prefer agents with lactation data.
Diet
Food & alcohol
- Food
- Food
Trust
Sources & disclaimer
Source: Local active-ingredient clinical extract; FDA drug label via OpenFDA/DailyMed; Professional class pharmacology (Therapeutic agent (verify pharmacological class))
Last reviewed: 01 Aug 2026
Decision support only — not a substitute for clinical judgment, product SmPC, or Kenya STG/EML.