Propylthiouracil: Everything You Need To Know!
Propylthiouracil (PTU) is a vital medication in managing hyperthyroidism, particularly in specific patient populations.
Propylthiouracil is used as an antithyroid agent for hyperthyroidism and Graves’ disease, and it is proven to be more effective than methimazole for thyrotoxic crises.
Our GMP-approved propylthiouracil API is a white-to-off-white, crystalline powder, 99% pure.
It is easily soluble in ethanol and acetone (16 mg/mL), but insoluble in water (approximately 1 mg/mL).
What is Propylthiouracil (PTU)?
Propylthiouracil (PTU) is a thioamide-class drug primarily used to treat hyperthyroidism, in which the thyroid gland produces excess hormones.
Approved by the FDA in 1947, PTU works by inhibiting the synthesis of thyroid hormone.
Unlike methimazole, another antithyroid drug, PTU also blocks the conversion of thyroxine (T4) to triiodothyronine (T3), the more active thyroid hormone.
This dual action is beneficial in severe cases, such as a thyroid storm.
PTU is available in 50 mg tablets and is typically prescribed for short-term use due to its risk profile. It’s often reserved for patients who cannot tolerate methimazole or during specific phases of pregnancy.
What Is Propylthiouracil Used For (What Does Propylthiouracil Do)?
PTU addresses several thyroid-related conditions:
Graves’ Disease: The most common cause of hyperthyroidism, an autoimmune disorder where antibodies stimulate excessive thyroid hormone production.
Thyroid Storm: A life-threatening exacerbation of hyperthyroidism requiring rapid hormone reduction. PTU’s ability to block T4-to-T3 conversion makes it first-line here.
Pre-Surgery Preparation: Patients undergoing thyroidectomy may use PTU to stabilize hormone levels preoperatively.
Radioactive Iodine Therapy Adjunct: PTU can be used to manage symptoms before or after radioactive iodine treatment.
PTU is generally preferred over methimazole in the first trimester of pregnancy and for those allergic to methimazole.
How Does Propylthiouracil Work? (Mechansim Of Action)
PTU’s mechanism of action involves two key actions:
Inhibition of Thyroid Peroxidase (TPO): TPO is an enzyme critical for iodine organification (binding to thyroglobulin) and thyroid hormone synthesis. PTU disrupts this process, reducing T4 and T3 production.
Blocking T4-to-T3 Conversion: Peripheral tissues convert T4 to T3. PTU inhibits type 1 deiodinase, the enzyme responsible for its effectiveness in acute settings, such as thyroid storm.
Effects begin within 24 hours, but symptom improvement may take weeks as pre-existing hormones are metabolized.
Propylthiouracil vs Methimazole (PTU vs MMI)
While both PTU and methimazole treat hyperthyroidism, their key differences influence their uses.
We have listed their key differences below in the table; take a look:
| Items | Propylthiouracil (PTU) | Methimazole |
|---|---|---|
| Mechanism | Blocks TPO and T4-to-T3 conversion | Only inhibits TPO |
| Dosing Frequency | Every 8 hours (3x daily) | Once daily |
| Pregnancy Use | Preferred in the first trimester | Avoid in the first trimester |
| Side Effect Profile | Higher risk of hepatotoxicity | Lower liver risk, but teratogenic |
| Onset of Action | Faster T3 reduction | Slower |
Methimazole is usually first-line due to its once-daily dosing and safer profile, except in pregnancy or thyroid storm.
Propylthiouracil Dosage and Administration
Adults: Initial dose is 100–150 mg every 8 hours, adjusted based on thyroid function test (TFT) results. Maintenance doses range from 50 to 150 mg daily.
Children: 5–7 mg/kg/day divided into three doses.
Thyroid Storm: Higher doses (200–400 mg every 6–8 hours) are used onforhort-term batreatment
Tips:
Take with food to reduce stomach upset.
Regular TFTs (every 4–6 weeks) guide dose adjustments.
What Are the Side Effects of Propylthiouracil?
PTU’s side effects range from mild to severe:
Common: Rash, joint pain, nausea, headache, metallic taste.
Serious:
Hepatotoxicity: Risk of liver failure, especially in children.
Agranulocytosis: Sudden drop in white blood cells, increasing infection risk.
Vasculitis: Inflammation of blood vessels, often presenting as skin lesions or kidney issues.
Hypothyroidism: Over-treatment can cause fatigue and weight gain.
Patients should seek immediate care for symptoms such as jaundice, a sore throat, or unexplained bruising.
Propylthiouracil Precautions and Drug Interactions
Contraindications:
Severe liver disease.
Allergy to PTU or thioamides.
Drug Interactions:
Warfarin: PTU potentiates anticoagulant effects.
Beta-Blockers: Often co-prescribed for symptom control.
Theophylline: PTU may increase its serum levels.
Precautions:
Monitor for infections (risk of agranulocytosis).
Avoid during breastfeeding due to minimal secretion into milk.
What to Monitor After Taking Propylthiouracil?
Regular monitoring ensures safety and efficacy after taking PTU.
What we need to monitor includes:
Thyroid Function Tests: TSH, T3, and T4 levels every 4–6 weeks.
Liver Enzymes: ALT/AST at baseline and periodically.
CBC: Check for agranulocytosis (sudden WBC drop).
Symptoms: Watch for rash, jaundice, or fatigue.
Is Propylthiouracil Safe During Pregnancy?
PTU is preferred during the first trimester due to methimazole’s teratogenic risks (e.g., choanal atresia).
However, PTU carries a low risk of liver toxicity, so guidelines recommend switching to methimazole after the first trimester.
Untreated hyperthyroidism poses more significant risks (preterm birth, preeclampsia), so therapy should continue with close monitoring.
Propylthiouracil in Special Populations
Pediatrics: Use cautiously due to the risk of hepatotoxicity; closely monitor liver enzymes.
Elderly individuals: Lower doses may be necessary due to slower metabolism.
Liver Impairment: Contraindicated in severe cases; avoid during mild-moderate disease unless necessary.
How Much Does Propylthiouracil API Cost?
The price of propylthiouracil powder depends on several aspects:
1. PTU Price with GMP and DMF
GMP and DMF prices can be double those of non-GMP factories.
If you need it for compounding or making tablets or capsules, you must use a GMP source.
Prices from the GMP factory in China are around 300 USD/kg.
Sources without GMP cost approximately 180 USD per kilogram for commercial order quantities.
2. Your order quantity
If you purchase it in commercial quantities, the unit price will be significantly lower than if you place a trial order.
It is just common sense.
For example, buying only one kilogram as a trial order will probably cost more than $ 400 per kilogram.
3. Purity requirements.
If 99% of common APIs cannot meet your purity requirements, such as requiring a single impurity of no more than 0.1% and total impurities of less than 0.5%, it will cost even more.
Take its reference standard. For example, 200 mg of USP RS costs approximately $ 4.00
How To Ship and Store Propylthiouracil API?
Propylthiouracil API powder has been tested and proven to be a safe chemical, suitable for shipment by air, courier, sea, or inland vehicles.
It is not flammable, explosive, oxidizing, toxic, radioactive, or corrosive.
No special packaging is required.
According to its stability tests, shelf life at room temperature is 3 years when protected from light and moisture, so you don’t need to ship and store it at low temperatures around 2~8 degrees Celsius.
Therefore, you can ship it under normal temperatures, ensuring it is well-sealed and protected from light and heat during transportation and storage.
Disclaimer:
This content is for informational purposes only and is intended for business-to-business communication within the pharmaceutical industry. It is not intended as medical advice. The manufacture, import, and use of API must comply with all applicable laws and regulations in the relevant country or region.
This blog post is informational only and does not constitute medical advice.
Always consult a healthcare professional before starting any new medication or treatment.
