Health Guide

Mercaptopurine (By mouth)

Mercaptopurine (mer-kap-toe-PURE-een)

Treats acute lymphoblastic leukemia.

Brand Name(s):


There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to mercaptopurine, or if you are pregnant.

How to Use This Medicine:

Liquid, Tablet

  • Medicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.
  • Your doctor will tell you how much medicine to use. Do not use more than directed.
  • Shake the bottle for at least 30 seconds to make sure the oral liquid is well mixed. Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup. Clean the dosing syringe with warm, soapy water after each use. Rinse the syringe well, and let it dry before you use it again.
  • Drink extra fluids so you will urinate more often and help prevent kidney problems.
  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.
  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Once opened, use the oral liquid within 8 weeks.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Do not use this medicine together with azathioprine unless your doctor tells you otherwise.
  • Some medicines can affect how mercaptopurine works. Tell your doctor if you are using allopurinol, mesalamine, olsalazine, sulfasalazine, trimethoprim-sulfamethoxazole, or warfarin.
  • This medicine may interfere with vaccines. Ask your doctor before you get a flu shot or any other vaccines.

Warnings While Using This Medicine:

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.
  • Tell your doctor if you are breastfeeding, or if you have kidney disease, liver disease, blood or bone marrow problems, autoimmune disease (including inflammatory bowel disease), or any type of infection (including Epstein-Barr virus, cytomegalovirus).
  • This medicine may cause the following problems:
    • Liver problems
    • Increased risk of new cancers, including skin cancer, cervical cancer
    • Low blood sugar in children
  • This medicine may make you bleed, bruise, or get infections more easily. Take precautions to prevent illness and injury. Wash your hands often.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
  • This medicine may make your skin more sensitive to sunlight. Wear sunscreen. Do not use sunlamps or tanning beds.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Bloody or black, tarry stools
  • Dark urine or pale stools, nausea, vomiting, loss of appetite, stomach pain, or yellow skin or eyes
  • Fever, chills, sore throat, cough, and body aches
  • Severe pain or swelling in your joints
  • Unusual bleeding, bruising, or weakness

If you notice these less serious side effects, talk with your doctor:

  • Darkening skin
  • Hair loss
  • Loss of appetite, nausea, vomiting, diarrhea

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 7/4/2018
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