6-Mercaptopurine (Generic Name)

Other Names: Purinethol, mercaptopurine, 6-MP

About This Drug

6-mercaptopurine is used to treat cancer. This drug is given by mouth.

Possible Side Effects (More Common)

  • Mild bone marrow depression. This is a decrease in the number of white blood cells, red blood cells, and platelets. Bone marrow depression usually happens 11 to 23 days after the drug is given, but may not happen for up to six weeks after the drug is given. This may raise your risk of infection, make you tired and weak (fatigue), and raise your risk of bleeding.
  • Soreness of the mouth and throat may happen with high doses of this drug. You may have red areas, white patches, or sores that hurt.
  • Changes in your liver function.  Your doctor will check your liver function as needed

Possible Side Effects (Less Common)

  • Skin and tissue irritation may involve redness, pain, warmth, or swelling at the IV site. This irritation happens if the drug leaks out of the vein into the nearby tissue. During the IV infusion, please tell your nurse right away if you experience pain, redness, or swelling at the site of the IV infusion.
  • Loose bowel movements (diarrhea) that may last for a few days.  This effect is rare, but is severe if it happens.
  • Headache
  • Red rash around the mouth, upper chest, and back of the hands. The rash may be scaly or raised.
  • Skin and nails may get darker. This effect is rare. This is often temporary and will fade when treatment is done.
  • Decreased appetite (decreased hunger)
  • Blood in the urine or stool
  • Crystals in the urine. This may happen with high doses of this drug.
  • Changes in lung tissue may happen with large amounts of this drug. These changes may not last forever, and your lung tissue may go back to normal. Sometimes these changes may not be seen for many years. You may get a cough or have trouble catching your breath.

Allergic Reactions

  • Allergic reactions including anaphylaxis are rare but may happen in some patients. Signs of allergic reaction to this drug may include swelling of the face, feeling like your tongue or throat are swelling, trouble breathing, rash (dry scaling), itching, fever, chills, feeling dizzy, and/or feeling that your heart is beating in a fast or not normal way.  If this happens, do not take another dose of this drug.  You should get urgent medical treatment.

Treating Side Effects

  • Mouth care is very important. Your mouth care should consist of routine, gentle cleaning of your teeth or dentures and rinsing your mouth with a mixture of 1/2 teaspoon of salt in 8 ounces of water or ½ teaspoon of baking soda in 8 ounces of water. This should be done at least after each meal and at bedtime.
  • Avoid mouthwash that contains alcohol. Also avoid alcohol and smoking because they can bother your mouth and throat.
  • Ask your doctor or nurse about medicine that is available to help stop or lessen the loose bowel movements.
  • Drink 6-8 cups of fluids every day unless your doctor has told you to limit your fluid intake due to another health problem. A cup is 8 ounces of fluid. If you throw up or have loose bowel movements, you should drink more fluids so that you do not become dehydrated (lack water in the body from losing too much fluid).
  • If you get a rash do not put anything on it unless your doctor or nurse says you may. Keep the area around the rash clean and dry. Ask your doctor for medicine if your rash bothers you.

Important Information

  • Take this drug at the same time every day.
  • Take on an empty stomach, at least 1 hour before eating or 2 hours after eating.
  • Store this drug at room temperature in a dry place.
  • Missed dose: If you miss a dose, take it as soon as you remember unless it is close to the time of your next dose.  Do not take 2 doses at once. Do not take extra doses.

Food and Drug Interactions

There are no known interactions of 6-mercaptopurine and any food. This drug is known to interact with allopurinol, olsalazine, azathioprine, febuxostat, and echinacea. If you are on any of these medicines or unsure if you are, talk to your doctor before starting this drug. This drug may also interact with other medicines. Tell your doctor and pharmacist about all the medicines and dietary supplements (vitamins, minerals, herbs and others) that you are taking at this time. The safety and use of dietary supplements and alternative diets are often not known. Using these might affect your cancer or interfere with your treatment. Until more is known, you should not use dietary supplements or alternative diets without your cancer doctor's help.

When to Call the Doctor

Call your doctor or nurse right away if you have any of these symptoms:

  • Fever of 100.5 F (38 C) or higher
  • Chills
  • Trouble catching your breath
  • Easy bleeding or bruising
  • Uncontrolled nausea that prevents you from eating or drinking
  • Throwing up more than twice in one day
  • Redness, pain, warmth, or swelling at the IV site
  • Chest pain
  • Blood in the urine
  • Crystals in the urine
  • Coughing
  • Feeling dizzy

Call your doctor or nurse as soon as possible if you have any of these symptoms:

  • Pain in your mouth or throat that makes it hard to eat or drink
  • Loose bowel movements (diarrhea) five or six times in one day or diarrhea with weakness or feeling lightheaded
  • Nausea that is not relieved by prescribed medicines
  • Headache that is not relieved by prescribed medicines
  • Skin or eyes get yellow
  • Lasting loss of appetite or weight loss of five pounds or more in one week
  • Extreme tiredness that interferes with normal activities
  • Rash that bothers you

Sexual Problems and Reproduction Concerns

  • Infertility warning: Sexual problems and reproduction concerns may happen. In both men and women, this drug may affect your ability to have children. This cannot be determined before your treatment. Talk with your doctor or nurse if you plan to have children.  Ask for information on sperm or egg banking.
    • In men, this drug may interfere with your ability to make sperm, but it should not change your ability to have sexual relations.
    • In women, menstrual bleeding may become irregular or stop while you are getting this drug. Do not assume that you cannot become pregnant if you do not have a menstrual period.
    • Women may go through signs of menopause (change of life) like vaginal dryness or itching. Vaginal lubricants can be used to lessen vaginal dryness, itching, and pain during sexual relations.
    • Genetic counseling is available for you to talk about the effects of this drug therapy on future pregnancies. Also, a genetic counselor can look at the possible risk of problems in the unborn baby due to this medicine if an exposure happens during pregnancy.
  • Pregnancy warning: This drug may have harmful effects on the unborn child, so effective methods of birth control should be used during your cancer treatment.
  • Breast feeding warning: Women are advised not to breast feed during treatment because this drug could enter the breast milk and seriously harm a breast feeding infant.

Revised August 2014

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