Purinethol (Mercaptopurine) is a purine antagonist that is prescribed along with other agents for the maintenance therapy of acute lymphocytic leukemia.





GSK, Aapen


25 mg




Brief overview of Purinethol

Purinethol, also known as mercaptopurine, plays a role in treating different medical conditions. With its ability to suppress the system, it has established itself as an essential component in healthcare.

Historical development and approval

Purinethols' journey started during the mid-20th century due to the search for effective treatments for leukemia. After undergoing clinical evaluations over time, the U.S. Food and Drug Administration (FDA) recognized its therapeutic potential and approved it.

Role in medical treatments

The origins of Purinethol can be traced back to its use in treating cancer. However, its applications have broadened over time to include treating conditions such as Crohn's disease and ulcerative colitis. Nowadays, it plays a role in both fields.

Uses of Purinethol

Primary medical indications

Purinethol is a medication that is used to treat acute lymphoblastic leukemia (ALL), a type of blood cancer that affects the blood cells. It is more common in children, but can also occur in adults1.

Crohn’s disease is an inflammatory bowel disease that primarily affects the gastrointestinal tract. It can cause pain, diarrhea, and other digestive symptoms. The inflammation caused by Crohn’s disease can involve different areas of the digestive tract in different people, most commonly the small intestine. This inflammation often spreads into the deeper layers of the bowel234.

Ulcerative colitis is another bowel disease that specifically affects the colon and rectum. It leads to ulcerations and inflammation in these areas resulting in symptoms like diarrhea and abdominal discomfort562.

Scope of its applications in healthcare

Purinethol has a range of applications in treating the mentioned conditions and as a supplementary therapy in various treatment plans. Its ability to regulate response makes it extremely valuable in transplant medicine and other autoinflammatory situations.

How It Works

Mechanism of action

Purinethols effectiveness relies on its capability to block the production of nucleotides, which stops the growth of cells, especially lymphocytes. Disrupting the S phase of the cell cycle effectively prevents cell growth.

Cellular impact and pharmacodynamics

At this level, Purinethol goes through a process of transforming into its active state called thioinosinic acid. This metabolite effectively hinders the production of purine nucleotides and interacts with the creation of DNA and RNA. As a result, it reduces the activity of cells that divide quickly, thereby exerting its impact.

Dosage and Administration

The usual recommendation for lymphoblastic leukemia is to start with 2.5mg per kilogram daily. However, for conditions such as Crohn's disease, it is generally suggested to use a lower dose, typically ranging from 1 to 1.5mg per kilogram per day. Nonetheless, adjusting the dosage according to each individual's response is crucial.

Route of administration

Purinethol should be taken by mouth. Following the dosage and watching for any adverse effects is crucial.

Duration of treatment and frequency

The timing of administering Purinethol is customized based on how the treatment works and the type of disease being treated. While certain conditions may call for long-term usage, others may require a duration, with regular observation.


Active and inactive ingredients

Mercaptopurine serves as the ingredient in the tablet alongside additional components, like starch, lactose, and magnesium stearate. These inactive ingredients contribute to the tablet's form and stability.

Formulations available in the market

Pharmaceutical companies have commonly produced 50mg tablets of this medication, making it widely available in healthcare environments.

Off-label Uses

Known off-label applications

Purinethol, also known as mercaptopurine, is a chemotherapy drug that is primarily used to treat acute lymphocytic leukemia 1However, it has also been used off-label to treat Crohn’s disease and ulcerative colitis 23It has also been used to treat histiocytosis X 2.

Clinical studies supporting off-label use

A few initial studies have provided insights into how effective it is for those situations mentioned. Nonetheless, extensive randomized trials are necessary to establish its role in these areas.

Controversies and debates on off-label applications

As with any medication, there are debates surrounding the off-label use of Purinethol. Some doctors believe in its effectiveness, while others request evidence to support its widespread use in these situations.

Side Effects

Understanding potential risks

Like any medication, Purinethol has a range of side effects. Healthcare professionals and patients must stay informed about these risks for a safe and effective treatment experience.

Short-term vs. long-term effects

Although immediate consequences could include sickness, throwing up, and skin irritation, prolonged usage can increase the likelihood of liver problems, decreased bone marrow function, and even the development of cancers. It is, therefore, crucial to monitor these conditions.

Common Side Effects

Most frequently reported adverse reactions

  • Gastrointestinal disturbances
  • Mild alopecia
  • Transient liver enzyme elevations

Management and mitigation strategies

Dealing with the outcomes requires a comprehensive strategy. This involves modifying the dosage, administering medications as needed, or, in extreme cases, even stopping the treatment altogether.


Drugs that may interact with Purinethol

Using this medication concurrently with allopurinol, warfarin, or ACE inhibitors may enhance its effects and potential side effects. It is crucial to provide a medication history to prevent any possible complications.

Potential outcomes of drug interactions

The range of outcomes varies from enhanced therapeutic effects to increased toxicity. Some may exhibit pronounced side effects, while others could impact its effectiveness.

Advice for concurrent medication usage

It's always important to seek advice from healthcare before starting any new medication. Regular checkups and periodic evaluations are crucial to ensure the possible results when taking multiple medications.


Cases where extreme caution is advised

Using Purinethol comes with its share of complexities. Patients with preexisting liver or kidney disorders must exercise caution when considering this treatment. Similarly, individuals who have known bone marrow suppression or are currently taking agents must undergo thorough evaluation before starting therapy.

Situations of heightened risk

When undergoing the process with Purinethol, it is essential to exercise caution in specific situations such as 1. Recent vaccinations 2. Concurrent use of medications that may harm the liver 3. Pending surgeries or invasive procedures: Being aware of these circumstances enables healthcare professionals to make decisions and minimize unnecessary risks.


Specific conditions or scenarios where Purinethol should not be used

Purinethol should not be used by patients allergic to mercaptopurine or any ingredients in the medication. Moreover, it is not recommended for individuals with liver problems or those who have had issues with thiopurine S methyltransferase (TPMT) deficiency.

Rationale behind contraindications

The reasons behind these contraindications are firmly rooted in prioritizing safety. People with the mentioned conditions or medical histories face a chance of experiencing severe adverse reactions, making the potential risks far greater than the potential benefits.

Careful Administration

Guidelines for special populations

For individuals with kidney problems or specific genetic variations, it may be necessary to adjust the dosage or consider treatments. It is crucial to customize treatment plans for these particular groups of people.

Monitoring parameters during treatment

Starting Purinethol requires a monitoring system, including regular liver function tests, complete blood counts, and assessments of renal function. This surveillance is crucial for identifying and addressing any potential adverse effects.

Important Precautions

Pre-treatment screenings

Before starting treatment with Purinethol, it is advisable to undergo an evaluation beforehand. This may involve testing to assess TPMT activity as well as assessments of liver and kidney function and a detailed examination of blood-related parameters.

Behavioral and dietary considerations while on medication

Patients taking Purinethol should be careful not to consume much alcohol and be cautious about the types of food they eat that could worsen gastrointestinal side effects. Additionally, they must avoid getting vaccinations and prioritize maintaining good hygiene to prevent potential complications.

Administration to Elderly

Dose adjustments if any

Considering the changes that occur with aging, it may be necessary to adjust the dosage for the elderly. This is important to accommodate the differences in how their bodies process medications and prevent a buildup of drugs.

Potential heightened risks or concerns

Elderly individuals may experience increased sensitivity to the effects of Purinethol. Additionally, when combined with medications, frailty, and age-related organ decline, there is a higher likelihood of adverse reactions in this population group.

Administration to Pregnant Women and Nursing Mothers

Risks to the fetus or infant

The use of Purinethol during pregnancy requires consideration due to its potential to cause birth defects. Exposure in the first trimester can present significant dangers to the developing baby.

Alternative treatments if necessary

When medical intervention is necessary, healthcare providers may consider alternative treatment plans with a better safety record for pregnant or breastfeeding individuals.

Recommendations for discontinuation during lactation

Due to the possibility of Purinethol metabolites being present in breast milk, nursing mothers are often advised to refrain from breastfeeding while undergoing treatment to protect their infants from harm.

Administration to Children

Age-specific dosage guidelines

Determining the dosage for children is a complex process considering factors such as body surface area. Healthcare professionals carefully calculate the dosage to ensure it achieves therapeutic levels without causing any potential harm.

Considerations for pediatric patients

Children, as they grow and develop, may experience side effects. Therefore, monitoring them and providing parents with proper education and guidance is crucial.

Over Dosage

Symptoms of Purinethol overdose

Overdosing, whether intentional, can have serious consequences, such as causing significant suppression of the bone marrow and liver damage and complications in the gastrointestinal system. Signs of this may include tiredness, yellowing of the skin or eyes (jaundice) and repeated infections.

Immediate interventions and management

Immediate medical attention is necessary in cases of overdosage. The management may include providing support addressing issues and taking specific actions to counteract the effects of the drug.


Optimal storage conditions

Keeping Purinethol in a dry location is crucial, away from direct sunlight and out of children's reach. Keeping the temperature between 15°C and 25°C is essential for maintaining the effectiveness and stability of the medication.

Shelf life and expiration considerations

It is essential to avoid using Purinethol after its expiration date as it may be less effective. Regularly checking medication supplies to prevent the use of expired medications is crucial.

Handling Precautions

Safe handling and disposal methods

When dealing with Purinethol, gloves are essential to avoid contact with the skin. In healthcare environments, using areas, drug preparation, and strict disposal protocols are necessary to prioritize the safety of patients and staff.

Measures to prevent contamination or accidental exposure

To ensure safety, it is essential to use pill dispensers, ensure child-proof caps are in place, and store the medication in its container. Also, it is crucial to avoid crushing or splitting tablets as this can help prevent exposure.

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