II. Indications

  1. FDA Approved (in combination regimens)
    1. Acute Lymphoblastic Leukemia (ALL)
  2. Off-Label Use
    1. Inflammatory Bowel Disease (Crohns Disease, Ulcerative Colitis)
    2. Cancer
      1. Acute promyelocytic Leukemia
      2. Autoimmune Hepatitis
      3. Lymphoblastic Lymphoma

III. Mechanism

  1. Mercaptopurine is a thiopurine derivative with antineoplastic and Immunosuppressant activity
  2. Mercaptopurine is a prodrug metabolized to active components by hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
    1. Metabolites inhibit interconversion between Nucleotides, inhibiting Purine and DNA synthesis
    2. Metabolites
      1. 6-thioGMP (6-thioguanosine-5'-phosphate)
      2. T-IMP (6-thioinosine monophosphate)
  3. Mercaptopurine is also a metabolized to deoxythioguanosine
    1. Deoxythioguanosine is a purine Nucleoside antimetabolite analog
    2. Incorporated into DNA in place of the Nucleoside Guanosine
    3. Interrupts DNA Replication
  4. Mercaptopurine is also metabolized to 6-methylmercaptopurine ribonucleoside (MMPR) by 6-thiopurine methyltransferase
    1. MMPR inhibits Purine synthesis

IV. Medications

  1. Mercaptopurine tablets: 50 mg
  2. Mercaptopurine oral solution: 20 mg/ml

V. Dosing

  1. See other references for disease specific dosing protocols
  2. Consider concurrent Folic Acid supplementation
  3. Inflammatory Bowel Disease (Crohns Disease, Ulcerative Colitis)
    1. Start (adult): 50 mg orally daily, then titrate to effect
    2. Adult and Child Dosing Range: 0.5 to 1.5 mg/kg orally daily
  4. Dose reduction indications (by >50%)
    1. Thiopurine methyltransferase (TPMT) Deficiency
    2. NUDT15 Gene Anomaly (Nudix Hydrolase 15 deficiency)

VI. Adverse Effects

  1. Alopecia
  2. Carcinogenic
    1. Case reports of T-Cell Lymphoma development after Mercaptopurine
  3. Myelosuppression
  4. Hepatotoxicity
  5. Hyperuricemia
  6. Hypoglycemia
  7. Lymphoproliferative Disorder
  8. Pancreatitis
  9. Photosensitivity
  10. Portal Hypertension

VII. Safety

  1. Avoid in Pregnancy (any trimester)
    1. Use reliable Contraception
  2. Avoid in Lactation
  3. Monitoring
    1. Complete Blood Count
    2. Liver Function Tests
    3. Renal Function tests

VIII. Drug Interactions

  1. Drugs that increase Mercaptopurine toxicity
    1. Allopurinol
    2. Trimethoprim Sulfamethoxazole

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Related Studies

Cost: Medications

mercaptopurine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
MERCAPTOPURINE 50 MG TABLET Generic $0.85 each