mer·cap·to·pu·rine (m r-k p t -py r  n)n. A purine analog that acts as an antimetabolite by interfering with purine synthesis, used primarily in the treatment of acute leukemia. |
mercaptopurine
mercaptopurine (6-MP),
drug class: antineoplastic-antimetabolite;
action: inhibits purine metabolism at multiple sites, which inhibits DNA and RNA synthesis;
uses: chronic myelocytic leukemia, acute lymphoblastic leukemia in children, acute myelogenous leukemia.
mercaptopurine (6-mercaptopurine, 6-MP) Warning - Hazardous drug!
Purinethol, Puri-Nethol (UK)
Pharmacologic class: Antimetabolite
Therapeutic class: Antineoplastic
Pregnancy risk category D
FDA Boxed Warning
• Don't give drug unless diagnosis of acute lymphatic leukemia is confirmed and responsible physician knows how to assess response to chemotherapy.
Action
Inhibits DNA and RNA synthesis, suppressing growth of certain cancer cells
Availability
Tablets: 50 mg
⊘Indications and dosages
➣ Acute lymphatic, myelogenous, or myelomonocytic leukemia
Adults and children: 2.5 mg/kg/day P.O. as a single dose, increased to 5 mg/kg/day after 4 weeks if response inadequate or if no toxicity occurs. On complete hematologic remission, give maintenance dosage of 1.5 to 2.5 mg/kg/day P.O. as a single dose (combined with other agents as prescribed).
Contraindications
• Hypersensitivity to drug or its components
• Prior resistance to drug or thioguanine
• Breastfeeding
Precautions
Use cautiously in:
• renal or hepatic impairment
• decreased platelet or neutrophil counts after chemotherapy or radiation
• pregnant patients.
Administration
• Follow facility protocols regarding proper handling and disposal of drug.
☞ Don't handle drug if you're pregnant.
• Be aware that total daily dosage is calculated to nearest multiple of 25 mg and given once daily.
☞ Withdraw drug immediately if white blood cell (WBC) or platelet count falls rapidly or steeply.
| Route | Onset | Peak | Duration |
| P.O. | Unknown | 2 hr | Unknown |
Adverse reactions
GI: nausea, vomiting, anorexia, diarrhea, GI ulcers, painful oral ulcers, pancreatitis
Hematologic: anemia, leukopenia , thrombocytopenia
Hepatic: jaundice, hepatotoxicity
Metabolic: hyperuricemia
Skin: rash, hyperpigmentation
Interactions
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
Patient monitoring
☞ 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.
Patient teaching
☞ 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.
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