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Mercaptopurine is a custom pharmacy drug. It is classified in the family of drugs known as purine antagonists. Mercaptopurine is predominantly utilized in the treatment of white blood cell origin cancers such as acute lymphoblastic leukemia and acute lymphatic leukemia. It is sometimes prescribed as a stand-alone drug or in concert with other chemotherapy drugs. Common alternative uses for this drug include: ulcerative colitis and Crohn's disease.


Mercaptopurine is most often administered once daily as a tablet or suspension. If your primary care physician prescribes mercaptopurine for once a day dosage, it should be taken at the same time each day. If you are prescribed a suspension, always use an oral syringe to precisely measure your dose. Be sure to thoroughly shake the bottle before measuring the dose to ensure that the medicine is properly distributed throughout prior to syringing.


Mercaptopurine may produce some unwanted side effects in select patients. Side effects may come on quickly or slowly appear; they may linger or grow in intensity. It is impossible to know which, if any, side effects you will experience until you begin taking this drug. Watch for side effects and contact your physician if any become worse or seem to be persisting. A list of some of the most likely side effects is below, but this is only a partial list and your experience may be different. The important thing to remember is to contact your physician if you experience anything that feels like it is worsening, or feels prolonged.

  • Vomiting and/or Nausea
  • Hair Loss
  • Rash
  • Darkening of Skin

Severe Side Effects:

It is possible to experience severe side effects while taking mercaptopurine. Not every patient will experience side effects. Those who do experience severe side effects should see their physician right away or go to an emergency medical facility for prompt treatment. A partial list of some of the known severe side effects is below.

  • Fever and/or Chills, Sore Throat
  • Signs of Infection
  • Pale Skin
  • Weakness
  • Short of Breath
  • Swelling in Stomach Area
  • Stomach Pain (upper right area)
  • Swelling (legs, feet, ankles)
  • Unusual Bruising
  • Abnormal Bleeding
  • Jaundice
  • No Appetite
  • Diarrhea


If you are considering the use of this drug, make an appointment to see your physician and have her or him review your medical history. Discuss your medications and current health status with your physician, as well as all your options, and then allow your physician to decide if mercaptopurine is safe for your use and appropriate for your treatment.

Ask your physician about possible contraindications relevant to you.

Mercaptopurine may be contraindicated for any of the following conditions. If you have any of the following, do not take mercaptopurine unless your physician gives you the go-ahead.

  • Kidney Disease
  • Impaired Kidney Function
  • Severe Loss of Body Water
  • Thiopurine S-Methyltransferase Deficiency
  • Decreased Bone Marrow Function
  • Anemia
  • Pregnancy
  • Ascites
  • Diminished Blood Platelets
  • Diminished White Blood Cells
  • Diminished Neutrophils
  • Hepatosplenic T-cell Lymphoma
  • Liver Problems
  • Abnormal Liver Function Tests
  • Blockage of Bile Flow
  • Acute Pancreas Inflammation
  • Stomach Ulcer
  • Intestinal Ulcer
  • High Bilirubin in Blood
  • "It is rare to find health professionals who are so willing to educate the patient on what they need to know."

    Clair C. | West Hollywood, CA