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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


6-Mercaptopurine. See Purinethol.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
tolerable dose, median 1.7 (1.5) 1.2 (0.8) <0.001 (IQR) Duration of AZA/6-MP 49.8 (32.0) 54.6 (31.0) 0.407 use, mo, median (IQR) AZA: azathioprine; 6-MP: 6-mercaptopurine; IQR: interquartile range; GI: gastrointestinal; NA: not applicable.
Finally, an in vitro study (10) suggested an alternative biochemical mechanism: XO inhibition by allopurinol may lead to preferential 6-MP oxidation via aldehyde oxidase, with the production of dihydroxy-6-MP, a compound responsible for feedback inhibition of TPMT activity.
Case 2.--A 53-year-old woman with Crohn disease receiving 6-MP monotherapy underwent liver biopsy for investigation of elevated aminotransferases.
Other reassuring reproductive safety information includes evidence that levels of maternal 6-MP found in cord blood and the placenta are very low, which possibly means the placenta blocks some of the passage of 6-MP from the mother to the fetus.
IBD is commonly treated with immunomodulators such as 6-mercaptopurine (6-MP) and its prodrug, azathioprine (AZA).
About 4% of patients on 6-MP or azathioprine will develop leukopenia, and up to 15% will have abnormal liver function test results.
6-mercaptopurine (6-MP)--an immunosuppressive drug found to be useful in closing fistulae and in reducing or eliminating dependence on corticosteroids in some patients with Crohn's disease.
* Probably safe drugs: 6-MP, azathioprine, ciprofloxacin, metronidazole, and cyclosporine.
This assay measures the TPMT-catalyzed transfer of the [sup.3]H-labeled methyl group from S-adenosylmethionine to 6-MP in lysed packed erythrocytes.
Present retrospectively examined the use of 6-mercaptopurine (6-MP) in 155 IBD patients with 325 pregnancies and 233 live births.
Such patients ought to be started on half-dose azathioprine or 6-mercaptopurine (6-MP) because they are at increased risk of early severe myelosuppression and resultant opportunistic infection in response to these agents.