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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.

6-mer·cap·to·pu·rine (Shy),

An analogue of hypoxanthine and of adenine; an antineoplastic agent.


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.

mercaptopurine, 6-mercaptopurine

an antimetabolite that acts by blocking purine synthesis; used as an antineoplastic agent, primarily in the treatment of leukemia and lymphosarcoma.
References in periodicals archive ?
The thiopurine antimetabolites azathioprine and 6-mercaptopurine are commonly used to treat inflammatory bowel disease; however, their administration at conventional doses is associated with adverse events and a lack of response in some patients.
A multicenter trial of 6-mercaptopurine and prednisone in children with newly diagnosed Crohn's disease.
Medical therapy for inflammatory bowel disease was grouped by class, including aminosalicylates, steroids, immune modulators (azathioprine, 6-mercaptopurine, methotrexate, and cyclosporine), and anti-TNF inhibitors (infliximab and adalimumab).
Myelosuppression: Patients receiving 6-mercaptopurine and methotrexate during maintenance are at risk for myleosuppression, which can be managed with dose delays and adjustments, depending on severity.
14,15) Several cytostatic agents incorporated in the front-line treatment of ALL have been shown to increase the incidence of secondary hematological malignancies: epipodophyllotoxins, alkylating agents, antracyclines and 6-mercaptopurine.
Metabolism of 6-mercaptopurine in the erythrocytes, liver, and kidney of rats during multiple-dose regimens.
Background: Genetic polymorphisms in thiopurine methyltransferase (TPMT) influence the metabolism of azathioprine (AZA) and 6-mercaptopurine (6-MP) in patients with inflammatory bowel disease (IBD).
Postoperatively, we doubled the dosage of his 6-mercaptopurine, which stabilized his nasal and laryngeal disease.
Azathioprine or 6-mercaptopurine are often effective as long-term therapy.
Azathioprine (AZA) and 6-Mercaptopurine (6-MP), immunosuppressant agents that are used most commonly in organ transplant patients and patients with rheumatoid arthritis, have also shown to be efficacious in inflammatory bowel disease.