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a purine analogue in which sulfur replaces the oxygen atom of purine; it is used as an antineoplastic agent primarily for treatment of acute lymphoblastic leukemia. It is also used an immunosuppressant in the treatment of Crohn's disease and ulcerative colitis. Called also 6-mercaptopurine and 6-MP.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

mercaptopurine (6-mercaptopurine, 6-MP)

Purinethol, Puri-Nethol (UK)

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

• Breastfeeding


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.

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


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.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved


A purine analog, C5H4N4S, that interferes with the synthesis of purines and is used primarily in the treatment of certain forms of leukemia.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


An antimetabolic chemotherapeutic structural analogue (thiol replaces 6-hydroxyl) of hypoxanthine, which is activated by hypoxanthine phosphoribosyl transferase and converted in vivo to thioinosinic acid, a competitive inhibitor in purine synthesis that targets rapidly dividing cells (e.g., in ALL, AML). The wide variation in 6-MP bioavailability and suboptimal doses during maintenance regimens are attributable causes for the high incidence of relapse in children with ALL in remission.

Adverse effects
Myelosuppression, anorexia, nausea, vomiting, jaundice.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


A CYTOTOXIC drug used in combination with others in the treatment of acute LEUKAEMIA. The drug is on the WHO official list. A brand name is Puri-Nethol.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
lewisi in both splenectomised and Cy-treated rats, while inhibition of its production by mercaptopurine led to the development of a moderate disease.
Identifying patients having high risk of developing toxicity with mercaptopurine is important as toxicity gives undue morbidity and mortality (7,8,22).
High-performance liquid chromatographic assay of the methyl and nucleotide metabolites of 6-mercaptopurine: quantitation of red blood cell 6-thioguanine nucleotide, 6-thioinosinic acid and 6-m ethyl mercaptopurine metabolites in a single sample.
leukemia is related to RBC methotrexate and mercaptopurine metabolites during maintenance chemotherapy.
Kinetics of mercaptopurine and thioguanine nucleotides in renal transplant recipients during azathioprine treatment.
Patients were also allowed to continue on whatever other drugs they were receiving for their illness, and these included p-aminosalicylic acid-containing agents, steroids, mercaptopurine, azathioprine, and antibiotics.
Mercaptopurine (MP), [4] the analog of hypoxanthine, is an antileukemic agent widely used to treat acute lymphoblastic leukemia (ALL) (1).
Mercaptopurine pharmacogenetics: monogenic inheritance of erythrocytes thiopurine methyltransferase activity.
Altered mercaptopurine metabolism, toxic effects and dosage requirement in a thiopurine methyltransferase-deficient child with acute lymphoblastic leukemia.
Patients with chronically active disease who appear to be "steroid dependent" may benefit from treatment with azathioprine or mercaptopurine in an effort to eliminate the use of corticosteroids.