Purinethol (Mercaptopurine)

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Mercaptopurine (Purinethol) works by blocking the growth of certain cancer cells. This drug may also be used to treat Crohn’s disease, ulcerative colitis, and lymphoma.

How should it be used?

This medication is available in tablet form.

  • Take exactly as instructed by your doctor.
  • Take by mouth with or without food with a full glass of water.
  • Drink plenty of fluids while taking this medicine.
  • Do not increase your dose or take this medicine more often than is prescribed.

Special Precautions/Instructions

Before taking this medicine tell your doctor about all of the following:

  • Medicines (including over the counter), vitamins, herbal products, and supplements that you are taking.
  • Have a problem (hypersensitivity) to mercaptopurine or any other ingredient in this medicine: – Mercaptopurine, corn and potato starch, lactose, magnesium stearate, and stearic acid
  • Have liver or kidney problems
  • Are pregnant, plan on becoming pregnant, or breastfeeding.

Women of childbearing age should avoid becoming pregnant.

Side Effects

  • Intestinal ulceration has been reported.
  • Nausea, vomiting, and anorexia are uncommon when medicine is started.
  • Mild diarrhea and sprue-like symptoms have been noted occasionally, but it is difficult at present to attribute these to the medication.
  • Oral lesions are rarely seen, and when they do they look like thrush rather than antifolic ulcerations.
  • An increased risk of pancreatitis may be associated with the investigational use of Purinethol in inflammatory bowel disease.
  • The administration of Purinethol has been associated with skin rashes and hyperpigmentation. Alopecia has been reported.

As this medication is used in cancer treatment, there are risks of bone marrow suppression and liver injury.

Contact your doctor if you experience: fever, sore throat, jaundice, nausea, vomiting, signs of local infection, bleeding from any site, or symptoms suggestive of anemia.

Contact your doctor immediately if you experience signs of an allergic reaction including:

  • Diarrhea
  • Feeling sick
  • Fever, shivering/chills, rash
  • Muscle and bone pain
  • Kidney problems (changes in the amount of urine or color of urine)
  • Tiredness, dizziness
  • Itching
  • Swelling
  • Trouble breathing

Carcinogenic potential exists in humans, but the extent of the risk is unknown. The effect on human fertility is unknown for either males or females.

Storage Conditions

This medication should be stored between 59-77 degrees F in a dry place. Keep out of reach of children and protect from light.


Call the national poison control center 1-800-222-1222 or 911 in the event of overdose. Symptoms of an overdose include vomiting, diarrhea, sore throat, fever, chills, and other signs of infection.