Propycil 50 mg

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Propycil 50 mg

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Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Propycil 50 mg

Quick Facts

Property Description
Active Ingredient Propylthiouracil (PTU)
Form Tablet (for oral administration)
Pharmacological Class Thioamide Antithyroid Agent
Primary Action Thyroid Hormone Synthesis Inhibitor
Origin Synthetic Thiocarbamide Compound

What Type of Medicine is Propylthiouracil (Propycil 50 mg)?

Propycil 50 mg is a prescription-only medicinal product containing the single active substance, Propylthiouracil (PTU), and is formally categorized as a Thioamide Antithyroid agent. This substance is a chemically synthetic thiocarbamide compound that is clinically recognized for its critical role in managing conditions characterized by an excessive output of thyroid hormones. Unlike agents that permanently damage the gland, Propylthiouracil functions as a reversible Thyroid Hormone Synthesis Inhibitor, positioning it as a pharmacological means of control.

Composition, Origin, and Form of the 50 mg Tablet

The composition of Propycil 50 mg includes the therapeutic compound Propylthiouracil at a precise strength of 50 mg per tablet, alongside various solid pharmaceutical excipients essential for the tablet’s structure. The 50 mg designation strictly verifies the mass of the active ingredient present in each unit dose, consistent with established international standards for the single-ingredient product. Propylthiouracil is particularly noted for its formulation’s suitability for a broad patient group.

General Therapeutic Purpose of Antithyroid Agents

The general therapeutic purpose of this Antithyroid agent is to help restore a proper metabolic balance by reducing the concentration of active thyroid hormones in the bloodstream. This is achieved through its primary action: blocking the enzyme thyroid peroxidase (TPO) within the thyroid gland, which is essential for constructing Thyroxine (T4) and Triiodothyronine (T3). This pharmacological intervention effectively manages the hormonal output and activation, stabilizing the body’s endocrine function.

Regulatory References

  1. NIH Drug Information

What side effects are possible with Propycil 50 mg?

Possible Side Effects and Safety Information: Propylthiouracil

The safety profile of Propylthiouracil (Propycil 50 mg) is formally defined by official government regulatory documents, which categorize adverse reactions based on their frequency and the body systems affected. The primary safety concerns highlighted across regulatory labels include the potential for severe hepatotoxicity (liver injury) and agranulocytosis (a severe reduction in white blood cells), both of which are classified as serious adverse reactions.


Official Adverse Reaction Classification

Adverse effects are grouped into System-Organ-Classes (SOCs). The label documents effects on the Blood and Lymphatic System Disorders, Hepatobiliary Disorders, Immune System Disorders (including vasculitis), and Skin and Subcutaneous Tissue Disorders.

Classification Examples of Documented Adverse Reactions
Common Nausea, vomiting, headache, rash, arthralgia (joint pain)
Uncommon Agranulocytosis
Rare Severe liver injury, ANCA-positive vasculitis

Regulatory Safety Notes

The onset of agranulocytosis is frequently noted in regulatory documents as a time-related safety pattern, often occurring early in the course of treatment, typically within the first few months. The risk of severe liver toxicity is identified as a critical safety concern in pediatric patients. Furthermore, the label contraindicates the use of Propylthiouracil in individuals with a history of severe liver injury from prior PTU exposure or severe hepatic impairment.

The safety profile dictates a structured risk assessment, distinguishing common and expected events from those that are serious, while also noting specific risks for certain patient populations, as defined by government health authorities.

Overdose and Emergency Response

Overdose and When to Seek Help

Official regulatory documents define the overdose profile of Propylthiouracil (Propycil 50 mg) by specifying documented clinical manifestations and mandated emergency actions. Immediate medical attention is required for any suspected overdose.


Documented Overdose Manifestations

Symptoms of overdose described in official prescribing information may include nonspecific findings such as nausea, vomiting, and epigastric distress, alongside headache, fever, arthralgia (joint pain), pruritus, and signs of pancytopenia.


Severe Outcomes and Emergency Response

The primary concern in overdose is the potential for severe systemic toxicities. These include potentially life-threatening outcomes such as acute liver failure (which has resulted in fatal outcomes in both adult and pediatric patients) and severe blood dyscrasias, notably agranulocytosis.

Due to this risk profile and the regulatory statement that no specific antidote is known, urgent medical action is necessary. Individuals must contact emergency services or a Poison Control Center immediately.

Management and Monitoring

Overdose management is centered on providing symptomatic and supportive treatment. Procedures like gastric lavage or the use of activated charcoal may be considered to reduce absorption. Following the acute phase, close surveillance is required. This involves monitoring vital signs, complete blood counts (CBC), and liver function tests due to the potential for delayed onset of severe hepatic and hematologic toxicity.

Therapeutic Uses of Propycil 50 mg

What Propycil 50 mg Treats: Main Uses and Benefits

Propycil (Propylthiouracil) is commonly used to address conditions characterized by periods of heightened symptoms associated with an overactive thyroid gland (hyperthyroidism), particularly Graves' disease and Toxic multinodular goiter. It is applied across domains where additional symptomatic support is needed to help achieve a controlled, euthyroid state, and contributes to easing the overall symptom load during periods of heightened symptoms. The medication may assist with managing symptom clusters related to heightened physiological activity.


The drug is relevant for easing symptoms related to systemic imbalance, such as unexplained weight loss and heat intolerance, and assists with addressing elevated heart rate (tachycardia) and palpitations. It is relevant for easing symptoms of increased neurological activity, like tremor and nervousness. Propycil is commonly used in clinical settings that involve acute or unstable symptom patterns, such as the management of a Thyroid Storm, and is used in settings where short-term symptom stabilization is important in patients who may be prepared for definitive treatments like thyroidectomy or Radioactive Iodine (RAI) therapy. It is considered relevant for use in the first trimester of pregnancy or when alternative antithyroid agents are not tolerated.


“It provides support that helps patients cope more steadily with difficult symptomatic episodes by addressing the systemic imbalance.”


Quick Fact: Supports Easing Symptoms related to heightened physiological activity
Symptom Domain Cardiovascular Overstimulation
Patient Benefit Contributes to easing symptoms related to heightened physiological activity like elevated heart rate and palpitations
Acute Use Context Used in clinical settings that involve acute or unstable symptom patterns

Eligibility and Restrictions for Use

Who Can and Cannot Use Propycil 50 mg?

The official eligibility for Propylthiouracil (Propycil 50 mg) is strictly defined by regulatory authorities and often reserved for specific populations. The medicine is primarily indicated for adults who are unable to tolerate the alternative drug, Methimazole, and for whom definitive treatments, like surgery or radioactive iodine therapy, are not suitable.

Absolute Contraindications and Non-Eligibility

Propylthiouracil must not be used if a patient has a known hypersensitivity to the drug or any of its components, or if they have a history of a severe adverse reaction (such as agranulocytosis or hepatitis) to any thiourea derivative. The medicine is also contraindicated in patients with severe hepatic impairment.

Age and Physiological Restrictions

Category Regulatory Status
Children under 6 Not recommended for use.
Pediatric Patients (6+) Use is conditional; generally not recommended unless Methimazole is not tolerated.
Pregnancy Reserved as the preferred antithyroid agent only during or just prior to the first trimester.
Renal Impairment Requires caution and a mandatory dose reduction based on the degree of impairment.

Eligibility in older adults (65 and over) is treated with caution due to insufficient clinical data and the higher frequency of decreased organ function.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Propylthiouracil (Propycil 50 mg) has documented interaction patterns with specific medicinal products, primarily based on its influence on thyroid status and potential effects on coagulation.

Interaction-Related Restrictions

Co-administration with Radio-iodine ( ^131 I) therapy is subject to a mandatory timing-based rule. Pre-treatment with Propylthiouracil may reduce the effectiveness of radio-iodine. Regulatory requirements state that the medicine must be withdrawn 2 to 4 days before irradiation to prevent this restriction.

For co-administration with oral anticoagulants like warfarin, Propylthiouracil may increase the anticoagulant activity due to the potential inhibition of Vitamin K activity. This effect requires consideration, and monitoring of prothrombin time is noted, particularly before surgical procedures.

Exposure-Modifying Interactions

As the patient's thyroid function normalizes (achieving a euthyroid state), this physiological change modifies the clearance of several co-administered drugs. Regulatory information indicates that the clearance of beta-adrenergic blocking agents (beta-blockers) may be reduced. Similarly, serum levels of Digitalis Glycosides and Theophylline may be increased due to decreased elimination rates linked to the restored thyroid status.

Food and Substances

Regulatory documentation confirms there are no known interactions between Propylthiouracil and standard foods or drinks. The potential effect of drinking alcohol while taking the medication is officially documented as unknown.

Mechanism of Action

Blocking New Hormone Assembly in the Thyroid

The primary mechanism involves the drug acting as an inhibitor of the enzyme Thyroid Peroxidase (TPO), located within the thyroid gland. By blocking TPO, PTU immediately suppresses the essential biochemical steps—iodination and coupling—required for synthesizing new Thyroxine (T₄) and Triiodothyronine (T₃) hormones. This causes a cessation of new T₄ and T₃ hormone synthesis .


◣ Reducing Hormone Activation in Peripheral Tissues

PTU also engages a secondary, systemic mechanism by inhibiting Type 1 Iodothyronine Deiodinase (ID-1), an enzyme primarily found in organs like the liver and kidney. Inhibition of ID-1 reduces the critical conversion of the less active T₄ pro-hormone into the highly potent active hormone, T₃. This dual action accelerates the decline in the overall active T₃ concentration in the bloodstream.


⏱️ The Mechanism's Time Constraint

It is essential to understand that the mechanism does not affect hormones already synthesized and stored in the thyroid gland. Because of this physiological limitation, the system-level change in hormone concentration is delayed until the existing reserve of stored hormones has been naturally metabolized and cleared from the system.

Dosage and Administration Information

Official Administration Guidelines

Propylthiouracil (Propycil 50 mg) is administered solely by the oral route using the 50 mg tablet formulation. The medicine is used following a structured two-phase titration schedule based on the patient's clinical status, with the total course of therapy typically spanning 1 to 2 years.


Standard Dosing and Frequency

The typical initial adult dose for hyperthyroidism is 300 mg daily, which is customarily divided into three equal portions taken at approximately eight-hour intervals. In cases of severe hyperthyroidism or very large goiters, the initial daily dose may be increased up to 600 mg to 900 mg. For total daily doses exceeding 300 mg, more frequent administration (every four to six hours) may be required to maintain consistent drug levels. Once the patient’s condition is stabilized (achieving a euthyroid state), usually after one to two months, the dose is gradually reduced (titrated) to a lower maintenance dose ranging from 50 mg to 150 mg daily.


Population-Specific Use and Adjustments

Official prescribing instructions mandate specific adjustments for certain populations. For children aged 6 to 10 years, the initial daily dose is typically 50 mg to 150 mg in divided doses. Dose adjustments are also explicitly required for patients with reduced kidney function: those with a glomerular filtration rate (GFR) between 10 and 50 mL/ min should receive 75% of the full dose, and patients with a GFR below 10 mL/ min should receive 50% of the full dose. In the first trimester of pregnancy, Propylthiouracil must be administered at the lowest effective dose. Regarding a missed dose, the instruction is to take it as soon as remembered unless it is almost time for the next scheduled dose, in which case the missed dose must be skipped without doubling the dose.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Propycil 50 mg

Evidence for Use in Managing Hyperthyroidism

The research base for Propylthiouracil (PTU) primarily involves controlled clinical trials, often called Randomized Controlled Trials (RCTs), which was studied for patterns in adults diagnosed with an overactive thyroid gland, such as those with Graves' disease. These studies monitored key outcomes related to systemic or functional imbalance, specifically tracking changes in thyroid hormone levels like T4 and T3. The research examined patterns related to hormone levels falling within a defined range (euthyroidism), and how those patterns were maintained.

Systematic reviews and comprehensive meta-analyses have also explored this area. The evidence level is categorized as High for research describing patterns related to hormone level changes over the immediate, short-term period. However, long-term research is often challenged because follow-up durations were limited in many studies. As a result, the certainty about the long-term patterns remains lower than for the initial short-term findings.

Evidence for Use in Acute Management and Preparation for Definitive Therapy

Research examined Propylthiouracil in two specific contexts where patients may experience conditions involving periods of heightened symptoms.

Acute Management (Thyroid Storm)

For the acute, severe presentation known as thyroid storm, evidence is limited to detailed clinical observations (case series) and consensus documents. Research here was studied for its application during episodes where symptoms become more noticeable, tracking acute care metrics like rapid changes in hormone levels. Data show patterns related to rapid biochemical changes, but comparative evidence is lacking.

Pre-treatment Before Definitive Therapy

Studies was studied for whether specific pre-treatment protocols showed patterns related to reaching a controlled hormone state before procedures like Radioactive Iodine (RAI) therapy. Findings were mixed regarding patterns of RAI treatment failure when Propylthiouracil had been used beforehand. Therefore, subgroup findings are uncertain concerning the most effective pre-treatment protocol, and the evidence quality varies across studies.

Evidence in Special Patient Populations

Propylthiouracil was evaluated in pregnant women with hyperthyroidism, specifically those included in research during the first trimester. The research base consists mainly of large observational cohorts and meta-analyses. While some studies have reported certain patterns, findings were mixed regarding absolute risk in comparison to alternative treatments, meaning certainty remains low for definitive conclusions about specific birth outcomes. The evidence provides context but not individual predictions, as findings describe group patterns, not personal outcomes.

Frequently Asked Questions (FAQ)

Common questions about Propycil 50 mg (FAQ)

Q: Does Propycil 50 mg cause weight gain or weight loss?

A: Official reports from safety monitoring indicate that weight changes have occurred in some patients taking Propylthiouracil. These reports include instances of both weight gain and a loss of appetite leading to weight loss. However, the exact frequency of these changes is not always clearly defined across all official documents.

Q: Can Propycil affect a person's mood or cause anxiety?

A: Regulatory documents have noted a variety of central nervous system (CNS) effects as reported adverse reactions. These symptoms include agitation, hostility, confusion, irritability, and depression. However, official information does not explicitly list anxiety as an adverse effect.

Q: What are the signs of liver issues related to Propycil?

A: The official medication guide describes potential signs of severe liver problems that require immediate medical review. These symptoms include yellowing of the skin or eyes, dark urine, pale stools, persistent nausea or vomiting, itching, and unexplained tiredness or fever. Official regulatory documents list these signs to help patients recognize when to seek prompt medical attention.

Q: Can Propycil 50 mg be crushed or split?

A: The medicine is provided solely as a 50 mg tablet intended for oral administration. The official labeling for the standard tablet does not contain instructions that explicitly permit crushing or splitting the tablet.

Q: Can Propycil cause hair loss?

A: Yes, regulatory adverse event summaries indicate that hair loss, also known as alopecia, has been reported as a side effect experienced during treatment with this medicine.

Q: Does Propycil interact with common over-the-counter pain relievers?

A: Official drug information advises caution regarding certain over-the-counter pain relievers. While interactions with Paracetamol (acetaminophen) are generally minor, the use of non-steroidal anti-inflammatory drugs (NSAIDs) and Aspirin has been shown to potentially affect the binding of T4 hormone in the blood.

Q: Is it normal to feel tired when first starting Propycil?

A: Official adverse effects summaries have included reports of tiredness, excessive weakness, drowsiness, and a general feeling of discomfort. This indicates that a feeling of being tired may be experienced by some patients initiating treatment.

Q: Is Propycil safe to use while breastfeeding?

A: Propylthiouracil is known to pass into human milk in small amounts. Official guidance outlines that the lowest effective dose should be used, and the nursing infant's status should be monitored for signs of infection or blood disorders. Recent findings regarding severe liver injury have led to changes in previous official advice for use during lactation.

Q: Why is Propycil sometimes used before thyroid surgery?

A: The medicine is used as a pre-treatment protocol to help optimize the patient's thyroid function to a controlled, or euthyroid, state before undergoing surgery. This pre-optimization is intended to minimize the risk of a severe, acute exacerbation of symptoms, known as a thyroid storm, during or shortly after the procedure.

Q: Are there restrictions on driving or operating machinery while taking this medicine?

A: While the official product label does not contain a formal restriction on driving, some reported adverse reactions include dizziness, drowsiness, and vertigo. These effects could potentially impair a person’s judgment or ability to safely operate machinery or vehicles.

Q: Does Propycil 50 mg need to be taken with food?

A: The official medication guide does not contain a specific instruction on whether the medicine must be taken with or without food. The administration schedule involves dividing the total daily amount into multiple doses taken at regular intervals.

Q: Can Propycil interact with herbal supplements?

A: Regulatory documents establish the need for physicians to be informed about all co-administered products, a category that explicitly includes vitamins and herbal supplements. This guidance exists because products not formally listed in the interaction section may still require medical review.

Q: What types of long-term monitoring are needed when taking Propycil?

A: Official information emphasizes the need for symptom vigilance due to the risk of rare, severe side effects. Regulatory documents state that patients should report symptoms of liver disease or agranulocytosis (low white blood cell count). If such symptoms arise, the official recommendation is for doctors to conduct monitoring, including liver function tests and the patient's complete blood count.

Q: Is it possible for the hyperthyroid condition to return after stopping Propycil?

A: Official information relating to the treatment of hyperthyroidism confirms that when antithyroid medicines are used as the sole therapy, there is a possibility that the condition may return after the medicine is discontinued. This potential for recurrence is a factor in treatment planning.

Q: Is Propycil also used to treat Graves' eye disease?

A: Propycil is an antithyroid agent used to treat the underlying hyperthyroidism caused by Graves' disease. Treatment for Graves' eye disease, also known as ophthalmopathy, is a separate concern that often requires different medical or surgical interventions, such as corticosteroids.

Q: Are generic versions of Propycil available?

A: Yes, the active ingredient in Propycil, which is Propylthiouracil, is officially available in generic formulations in markets like the U.S.

Q: Can Propycil affect my fertility?

A: Studies conducted on laboratory animals have reported effects on the reproductive system, including observations of infertility in some models. Specific details regarding the direct human fertility risk are not consistently present in the primary regulatory labels.

Q: Does Propycil 50 mg affect cholesterol levels?

A: While the medicine treats an overactive thyroid, clinical studies have noted a trend that anti-thyroid drug treatment can lead to an increase in total cholesterol and LDL-cholesterol levels. This effect is often observed as the thyroid function returns to a normal, or euthyroid, state.

Q: What should I know about Propycil and dental procedures?

A: Regulatory guidance highlights the need for a physician's review before a patient undergoes any dental work. For invasive procedures, official information suggests that monitoring for potential bleeding issues or the risk of agranulocytosis (low white blood cell count) may be necessary, possibly involving a complete blood count test.

Q: Can I take vitamins while using Propycil?

A: Official drug interaction guides specify that a physician must be informed about all medications a patient is taking, and this explicitly includes vitamins. This ensures all potential interactions are reviewed by a medical professional.

Q: Does Propycil have a 'Black Box Warning'?

A: Yes, Propylthiouracil has been assigned a specific safety notice known as a Black Box Warning in regulatory documents. This is the strongest type of warning, highlighting the elevated risks of severe liver injury and acute liver failure associated with its use.

Q: Can Propycil affect my sense of taste or smell?

A: Yes, official summaries of reported side effects include both the loss of taste and a phenomenon known as taste perversion. These are potential, but generally uncommon, adverse effects associated with the medicine.

How should Propycil 50 mg be stored and disposed of?

Official Storage Conditions and Disposal of Propylthiouracil

Propylthiouracil tablets must be stored under defined conditions to maintain stability and prevent degradation, as required by regulatory labeling.

Storage Requirement Official Specification
Temperature Range Controlled room temperature (20 C to 25 C / 68 F to 77 F)
Environmental Control Store away from excessive heat and moisture. Do not freeze.
Container & Safety Keep in a closed container and securely out of the reach of children.
Disposal Rule Consult a healthcare professional on how to dispose of any outdated or unused product. Do not keep medicine that is no longer needed.

The official storage conditions mandate a controlled room temperature and protection from environmental extremes like excessive heat and freezing. The medicine must remain in a closed container and be kept away from children. Proper disposal requires discarding expired product and following professional guidance on safe discard procedures for unused portions.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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