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mercaptopurine (6-mercaptopurine, 6-MP)
Pharmacologic class: Antimetabolite
Therapeutic class: Antineoplastic
Pregnancy risk category D
FDA Box Warning
• Don't give drug unless diagnosis of acute lymphatic leukemia is confirmed and responsible physician knows how to assess response to chemotherapy.
Inhibits DNA and RNA synthesis, suppressing growth of certain cancer cells
Tablets: 50 mg
Indications and dosages
➣ Maintenance therapy for acute lymphatic (lymphocytic, lymphoblastic) leukemia
Adults and children: On complete hematologic remission, 1.5 to 2.5 mg/kg/day P.O. as a single dose (combined with other agents as prescribed).
• Hypersensitivity to drug or its components
• Prior resistance to drug or thioguanine
Use cautiously in:
• renal or hepatic impairment
• decreased platelet or neutrophil counts after chemotherapy or radiation
• inherited thiopurine methyltransferase deficiency
• pregnant patients.
• Follow facility protocols regarding proper handling and disposal of drug.
☞ Don't handle drug if you are pregnant.
• Be aware that total daily dosage is calculated to nearest multiple of 25 mg and given once daily.
☞ Be aware that when mercaptopurine is given with allopurinol, mercaptopurine dosage must be reduced to one-third to one-fourth of usual dosage to avoid severe toxicity.
☞ Withdraw drug immediately if white blood cell (WBC) or platelet count falls rapidly or steeply.
GI: nausea, vomiting, anorexia, diarrhea, GI ulcers, painful oral ulcers, pancreatitis
Hematologic: anemia, leukopenia, thrombocytopenia
Hepatic: jaundice, hepatotoxicity
Skin: rash, hyperpigmentation
Drug-drug. Allopurinol (more than 300 mg), aminosalicylate derivatives (mesalazine, olsalazine, sulfasalazine): increased bone marrow depression
Warfarin: decreased anticoagulant effect
Drug-diagnostic tests. Hemoglobin, platelets, red blood cells, uric acid, WBCs: increased values
☞ Watch for signs and symptoms of hepatotoxicity.
• Monitor weekly CBC with white cell differential and platelet count.
• Assess bone marrow aspiration and biopsy results, as necessary, to aid assessment of disease progression, resistance to therapy, and drug-induced marrow hypoplasia.
• Monitor serum uric acid level.
• Evaluate fluid intake and output.
• Monitor liver function tests and bilirubin level weekly at start of therapy, then monthly.
☞ Instruct patient to immediately report fever, sore throat, increased bleeding or bruising, or signs or symptoms of liver problems (right-sided abdominal pain, yellowing of skin or eyes, nausea, vomiting, clay-colored stools, or dark urine).
• Advise both male and female patients to use reliable contraception.
• Encourage patient to maintain adequate fluid intake.
• Caution patient not to get vaccinations without consulting prescriber.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.