Mercaptopurine: Treatment for ALL, Crohn's & Colitis
Mercaptopurine is a purine analogue and antimetabolite used primarily as an antineoplastic and immunosuppressive agent. It works by interfering with nucleic acid synthesis, preventing the replication of fast-dividing cells like cancer cells or overactive immune cells.
Mercaptopurine is a crucial component of maintenance therapy for acute lymphoblastic leukemia (ALL), significantly reducing the risk of relapse.
Beyond oncology, it is widely utilized in gastroenterology as a steroid-sparing agent to maintain long-term remission in inflammatory bowel diseases (IBD), such as Crohn's disease and ulcerative colitis.
Indications
- Leukemia: Maintenance therapy for Acute Lymphoblastic Leukemia (ALL) in adults and children. Also used in some regimens for Acute Myeloid Leukemia (AML).
- Gastrointestinal: Off-label but standard clinical use for maintaining remission in Crohn's disease and Ulcerative Colitis.
Dosage and administration
The dosage is highly individualized based on body surface area or body weight.
- Standard Leukemia Dose: Typically 2.5 mg/kg or 50 to 75 mg/m² of body surface area per day.
- Administration: Take as a single daily dose at the same time each day. Do not take with milk or dairy products, as they contain an enzyme (xanthine oxidase) that degrades the drug.
- Critical Interaction: If co-administered with allopurinol (or febuxostat), the Mercaptopurine dose must be reduced to 25% of the standard dose to avoid life-threatening bone marrow toxicity.
- Pregnancy and breastfeeding (highly teratogenic).
- Profound bone marrow suppression (severe neutropenia or thrombocytopenia).
- Severe hepatic or renal impairment.
- Active severe infections.
Frequent blood tests and liver function monitoring are mandatory during therapy.
- Hematologic: Bone marrow suppression (leukopenia, thrombocytopenia, anemia), increasing the risk of serious infections and bleeding.
- Hepatic: Hepatotoxicity, including jaundice and elevated liver enzymes.
- Gastrointestinal: Nausea, vomiting, anorexia, stomatitis.
- Other: Increased risk of pancreatitis (especially in IBD patients).
