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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.

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.




abbreviation for 6-mercaptopurine. See mercaptopurine.


6-Mercaptopurine. See Purinethol.


References in periodicals archive ?
5] Nonstandard abbreviations: AZA, azathioprine; 6-MP, 6-mercaptopurine; 6-TGN, 6-thioguanine nucleotide; 6-MMPR, 6-methylmercaptopurine ribonucleotide; TPMT, thiopurine S-methyltransferase; TNF-[alpha], tumor necrosis factor-[alpha]; IBD, inflammatory bowel disease; XO, xanthine oxidase; HPRT, hypoxanthineguanine phosphoribosyltransferase; 6-MMP, 6-methylmercaptopurine; 5-ASA, 5-aminosalicylic acid.
6-MP is converted nonenzymatically to 6-thioguanine (6-TGN), the biologically active metabolite responsible for the therapeutic response.
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.
10] Nonstandard abbreviafions: 6-MP, 6-mercaptopurine; aza, azathioprine; IBD, inflammatory bowel disease; TPMT, thiopurine S-methyltransferase; TTPA, Inosine triphosphatase; ADR, adverse drug reacfion; 6-TGN, 6-thioguanosine nucleotide; OR, odds ratio; and CI, confidence interval.
It's unnecessary to routinely monitor 6-thioguanine nucleotide (6-TGN), the active metabolite of azathioprine and 6-MP.
Erythrocyte TPMT activity was measured in EDTA blood as the conversion of 6-MP to 6-MeMP (16) and expressed as picomoles of 6-MeMP formed per hour per milligram of hemoglobin [pmol 6-MeMP * [h.
To our knowledge, this is the first LC/MS/MS method developed to quantify 6-TGNs and 6-MMPNs, the 2 major metabolites of azathioprine and 6-MP present in erythrocytes.
1] Nonstandard abbreviations: 6-MP, 6-mercaptopurine; TPMT, thiopurine methyltransferase; ORF, open reading frame; FRET, fluorescence resonance energy transfer; TAMRA, 6-carboxytetramethylrhodamine; [T.
Few HPLC methods have been developed for the determination of thiopurine and methylated thiopurine metabolites of azathioprine or 6-MP in biological fluids [7-9].
6-MP and its metabolites can be methylated by thiopurine methyltransferase (TPMT).
The investigators postulated that the AZA-induced increase in TPMT activity reflects appropriate conversion of AZA to 6-MP by glutathione S-transferases and therefore reflects the immunosuppressive potency of the drug [5].