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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-mer·cap·to·pu·rine (Shy),

An analogue of hypoxanthine and of adenine; an antineoplastic agent.
Farlex Partner Medical Dictionary © Farlex 2012


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.
References in periodicals archive ?
While 6-mercaptopurine journeyed from the lab to the doctor's office in just two years, taxol required three decades.
Moreno-Otero, "6-Mercaptopurine or methotrexate added to prednisone induces and maintains remission in steroid-dependent inflammatory bowel disease," European Journal of Gastroenterology & Hepatology, vol.
The therapy generally based on VP regimen (VCR 1.4 mg/m [sup]2 , maximum 2 mg, i.v., days 1 and 8; Pred 30-40 mg/d, p.o., days 1-14), and multiple myeloma regimen (6-mercaptopurine 60 mg?m [sup]-2?d [sup]-1 , generally 100 mg/d, p.o., days 1-14; MTX 20 mg?m [sup]-2?d [sup]-1 , generally 30 mg/d, p.o., days 1 and 8) was administered alternatively.
During this hospitalization, the 6-mercaptopurine and infliximab were discontinued, but the patient remained on low dose corticosteroids.
The indication is for "reducing signs and symptoms and inducing and maintaining clinical remission in patients 6 years of age and older with moderately to severely active Crohn's disease who have had an inadequate response to corticosteroids or immunomodulators such as azathioprine, 6-mercaptopurine, or methotrexate."
The drug, 6-mercaptopurine (MP), is one of anticancer drugs that belong to the class of antimetabolites which can be used to treat different types of diseases such as inflammatory bowel disease, pediatric non-Hodgkins lymphoma, and leukemia [1].
6-Mercaptopurine and 6-thioguanine have been found in 1950s [1, 2].
During the second quarter the Food and Drug Administration approved Simponi (golimumab) for the treatment of moderately to severely active ulcerative colitis in adult patients who have demonstrated corticosteroid dependence or who have had an inadequate response to or failed to tolerate oral aminosalicylates, oral corticosteroids, azathioprine or 6-mercaptopurine.
In rheumatoid arthritis, methotrexate was the most effective companion agent, while in Crohn's disease, azathioprine and 6-mercaptopurine seemed to be effective in preventing AABs.
The patient was switched to another thiopurine drug, 6-mercaptopurine (6-MP), at 75 mg/day (1.4 mg x [kg.sup.-1] x [day.sup.-1]), which was well tolerated but similarly ineffective (8 stools daily).
Janssen Biotech, a biotechnology company that was founded in Philadelphia, has received FDA approval for Simponi (golimumab) to treat moderately to severely active ulcerative colitis in adult patients with corticosteroid dependence or an inadequate response to or failure to tolerate oral aminosalicylates, oral corticosteroids, azathioprine, or 6-mercaptopurine, it was reported yesterday.
Drugs that interfere with niacin or tryptophan metabolism, such as isoniazid, pyrazinamide, 6-mercaptopurine, 5-flurouracil, phenytoin, azathioprine, chloramphenicol, and ethionamide can also cause pellagra-like symptoms.