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Mercaptopurine is available as a pill you can swallow. It is sometimes called 6-mercaptopurine, or 6-MP.

How It Works

Mercaptopurine stops cells from growing and dividing.

Why It Is Used

Mercaptopurine is used to treat acute lymphoblastic leukemia (ALL). It may also be used when chronic myelogenous leukemia (CML) becomes a more aggressive disease and, very rarely, for acute myelogenous leukemia (AML).

Mercaptopurine is also sometimes used to treat non-Hodgkin's lymphoma, inflammatory bowel disease, Crohn's disease, and ulcerative colitis that has not responded to other drugs.

How Well It Works

Mercaptopurine works well against some ALL, CML, and a type of non-Hodgkin's lymphoma called lymphoblastic lymphoma.1 It sometimes works well in the treatment of inflammatory bowel disease, Crohn's disease, and ulcerative colitis that has not responded to other drugs.

Side Effects

Side effects of mercaptopurine are common and may include:

  • Nausea or vomiting.
  • Loss of appetite.
  • Mouth sores.
  • Changes in the way things taste.
  • Diarrhea.
  • Changes in liver function.
  • Rash, which may itch.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Mercaptopurine is usually used only under the supervision of a medical oncologist or hematologist. It may also be used by a gastroenterologist to treat inflammatory bowel disease.

Mercaptopurine may increase the blood-thinning effects of other drugs, such as warfarin (for example, Coumadin).

You may not be able to become pregnant or father a child after taking mercaptopurine. Talk about this with your doctor before starting treatment.

Mercaptopurine can cause birth defects. Do not use this drug if you are pregnant or wish to become pregnant or to father a child while you are taking it.

Women who take this drug may experience symptoms of menopause, including hot flashes and vaginal dryness.

Do not use alcohol or illegal drugs while you are taking this drug.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. Itakura H, Coutre SE (2009). Acute lymphoblastic leukemia in adults. In JP Greer et al., eds., Wintrobe's Clinical Hematology, 12th ed., vol. 2, pp. 1821–1842. Philadelphia: Lippincott Williams and Wilkins.


By Healthwise Staff
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer Brian Leber, MDCM, FRCPC - Hematology
Last Revised February 9, 2011

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.