From the Guidelines
Purixan, a liquid form of mercaptopurine (6-MP), is an oral chemotherapy medication that should be used with caution due to its potential for severe toxicity, particularly in patients with thiopurine methyltransferase (TPMT) deficiency, and its standard dosage typically ranges from 1.5 to 2.5 mg/kg body weight per day, though this may be adjusted based on individual patient factors and response 1.
Key Considerations
- Purixan works by interfering with DNA synthesis in rapidly dividing cells, preventing cancer cells from multiplying, and is primarily used to treat acute lymphoblastic leukemia (ALL) in both children and adults.
- The medication comes as a 20 mg/mL oral suspension, making it easier to administer precise doses, especially for children or patients who have difficulty swallowing pills.
- Regular blood tests are essential during treatment to monitor for bone marrow suppression, liver toxicity, and other side effects, as azathioprine, a related medication, has been associated with pancytopenia, autoimmune hemolytic anaemia, leukopenia, thrombocytopenia, macrocytosis, and pure red cell aplasia 1.
- Patients should take Purixan on an empty stomach, at least one hour before or two hours after meals, and at the same time each day for consistent blood levels.
- Genetic variations in the TPMT and NUDT15 enzymes can affect how patients metabolize this medication, potentially requiring dose adjustments to prevent severe toxicity, and TPMT testing may be performed prior to initiation of azathioprine therapy in patients with autoimmune hepatitis (AIH) to ensure safety and reassurance 1.
Side Effects and Monitoring
- Common side effects of Purixan include nausea, decreased blood counts, and elevated liver enzymes.
- Close monitoring of all patients started on azathioprine is mandatory, even following TPMT activity testing, as azathioprine toxicity is more frequently encountered in the absence of TPMT deficiency.
- Patients with TPMT deficiency may require alternative treatment regimens, such as prednisolone monotherapy or a lower dose of prednisolone combined with mycophenolate mofetil (MMF), to minimize the risk of severe toxicity.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Purixan (Mercaptopurine) Overview
- Mercaptopurine (6MP) is a medication used to treat acute lymphoblastic leukemia (ALL) and other conditions.
- It is metabolized by the body to form 6-thioguanine nucleotide (6TGN), which has anti-leukemic effects, and 6-methylmercaptopurine (6MMP), which can cause toxic effects 2, 3.
Mechanism of Action and Metabolism
- 6MP inhibits de novo purine synthesis, which is a mechanism of its anti-leukemic effects 4.
- Allopurinol can modify 6MP metabolism to favor 6TGN production and reduce 6MMP, which can help reduce toxicity and improve efficacy 2, 5.
Clinical Studies and Outcomes
- Studies have shown that allopurinol can safely correct skewed 6MP metabolism, improving inadequate myelosuppression and reducing gastrointestinal toxicity in patients with ALL 2, 5.
- The combination of 6MP and methotrexate has been shown to produce greater anti-leukemic effects and de novo purine synthesis inhibition compared to 6MP alone 4.
- Microbiome changes have been implicated in the anti-inflammatory response of 6MP in ALL mice models, with short-chain fatty acids playing a role in improving ALL progression 6.