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ANTINEOPLASTIC AND IMMUNOMODULATING AGENTS › ANTINEOPLASTIC AGENTS › ANTIMETABOLITES › Purine analogues
mercaptopurine
L01BB02
Adult Dosing
- Acute lymphoblastic leukemia (ALL): 1.5 to 2.5 mg/kg/day (or 50 to 75 mg/m²/day) as a single daily dose
- Adjust dose based on absolute neutrophil count (ANC) and platelet nadir to maintain target myelosuppression
- Reduce dose by 50-75% when co-administered with allopurinol
Pediatric Dosing
- Acute lymphoblastic leukemia (ALL) in children: 1.5 to 2.5 mg/kg/day (or 50 to 75 mg/m²/day) as a single daily dose
- Adjust dose based on toxicity and hematologic response
Indications
- Maintenance therapy for acute lymphoblastic leukemia (ALL) as part of a combination regimen
- Management of Crohn's disease and ulcerative colitis (off-label)
Mechanism of Action
- Purine antimetabolite that acts as a structural antagonist of hypoxanthine and guanine
- Undergoes intracellular conversion to active thiopurine nucleotides (e.g., 6-thioguanine nucleotides) which are incorporated into DNA and RNA, inhibiting purine synthesis and cell proliferation
Contraindications
- Hypersensitivity to mercaptopurine or any component of the formulation
- Prior resistance with mercaptopurine or azathioprine (cross-sensitivity)
- Severe bone marrow suppression
Adverse Reactions
- Myelosuppression (leukopenia, thrombocytopenia, anemia)
- Hepatotoxicity (elevated transaminases, jaundice, cholestasis, hepatic necrosis)
- Gastrointestinal toxicity (nausea, vomiting, anorexia, diarrhea, stomatitis)
- Immunosuppression leading to increased risk of opportunistic infections
- Secondary malignancies (e.g., skin cancers, lymphoproliferative disorders)
Drug Interactions
- Allopurinol: inhibits xanthine oxidase, increasing mercaptopurine concentrations and risk of severe toxicity; reduce mercaptopurine dose by 75%
- Aminosalicylates (e.g., mesalamine, olsalazine, sulfasalazine): inhibit TPMT enzyme, increasing risk of myelosuppression
- Warfarin: mercaptopurine may inhibit the anticoagulant effect of warfarin
- Myelosuppressive agents: additive bone marrow suppression and increased infection risk
Curated Content: Needs Vetting Before Put to Clinical Use