Mercaptopurine is used to treat acute lymphoblastic or lymphocytic leukemia. Mercaptopurine is sometimes given with other cancer medications.

Mercaptopurine may also be used for purposes not listed in this medication guide.

You should not use mercaptopurine if you have ever used mercaptopurine or thioguanine and they were not effective in treating your condition.

Some people using mercaptopurine have developed a rare fast-growing type of lymphoma (cancer). This condition affects the liver, spleen, and bone marrow, and it can be fatal.

Call your doctor at once if you have symptoms of lymphoma, such as: fever, night sweats, tiredness, stomach bloating, feeling full, easy bruising or bleeding, or weight loss.

Mercaptopurine comes as a tablet and a suspension (liquid) to take by mouth. It is usually taken once a day. Take mercaptopurine at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take mercaptopurine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

If you are taking the suspension, shake the bottle very well for 30 seconds before each use to mix the medication evenly. It is important to use an oral syringe (measuring device) to accurately measure and take your dose of mercaptopurine. If you do not find an oral syringe with your medication, ask your pharmacist to give you one. After you use the oral syringe to take your medication, remove the plunger from the rest of the measuring device, wash both parts with warm soapy water, and rinse under running tap water. Allow the parts to air dry before putting back together for the next use.

Continue to take mercaptopurine even if you feel well. Do not stop taking mercaptopurine without talking to your doctor

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Shake the oral suspension (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Use care when handling mercaptopurine tablets or oral suspension. mercaptopurine may be dangerous if it gets in your eyes or on your skin. If this occurs, wash your skin with soap and water or rinse your eyes with water. Seek medical attention if you have redness, itching, or swelling even after rinsing off the medicine. Ask your doctor or pharmacist how to dispose of unused medicine no longer needed.

Mercaptopurine can increase your risk of bleeding, infection, or liver problems. You will need frequent medical tests. Your next dose may be delayed based on the results.

Mercaptopurine can affect your kidneys. Drink plenty of liquids to keep your kidneys working properly.

You may be given other medication to help prevent serious side effects on your kidneys. Keep using this medicine for as long as your doctor has prescribed.

Store mercaptopurine at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

You should not use this medicine if you are allergic to mercaptopurine or thioguanine, or if you have ever used mercaptopurine or thioguanine and they were not effective in treating your condition.

Mercaptopurine may cause a rare type of lymphoma (cancer) of the liver, spleen, and bone marrow that can be fatal. Talk with your doctor about your own risk.

Using mercaptopurine may also increase your risk of developing other types of cancer. Ask your doctor about your specific risk.

Tell your doctor if you have ever had:

• liver disease;

• kidney disease;

• an inherited condition in which your body cannot produce enough of the enzyme thiopurine methyltransferase (TPMT);

• any type of viral, bacterial, or fungal infection; or

• ulcerative colitis (treated with mesalamine, sulfasalazine, or similar medicines).

Mercaptopurine may harm an unborn baby, especially when used during the first trimester. Use effective birth control to prevent pregnancy, and tell your doctor if you become pregnant.

You should not breastfeed while taking mercaptopurine.

Call your doctor for instructions if you miss a dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Early symptoms of an overdose may include loss of appetite, nausea, vomiting, or diarrhea. Later symptoms may include fever or flu-like symptoms.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Mercaptopurine suspension can be kept at room temperature for up to 8 weeks after the bottle is opened for the first time. Then, dispose of any suspension that is left over after 8weeks.

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unless your doctor tells you otherwise, continue your normal diet.

Do not receive a "live" vaccine while using mercaptopurine. The vaccine may not work as well and may not fully protect you from disease. Live vaccines include measles, mumps, rubella (MMR), polio, rotavirus, typhoid, yellow fever, varicella (chickenpox), zoster (shingles), and nasal flu (influenza) vaccine.

Avoid being near people who are sick or have infections. Tell your doctor at once if you develop signs of infection.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Mercaptopurine may cause serious side effects. Call your doctor at once if you have:

• low blood cell counts--fever, chills, tiredness, mouth sores, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet, feeling light-headed or short of breath;

• liver problems--loss of appetite, nausea, vomiting, diarrhea, upper stomach pain, swelling in your midsection, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or

• symptoms of lymphoma--fever, night sweats, tiredness, stomach bloating, feeling full, weight loss.

Common side effects of mercaptopurine may include:

• low blood cell counts;

• bruising or bleeding;

• nausea, vomiting, loss of appetite;

• diarrhea;

• rash, changes in skin color;

• hair loss; or

• general ill feeling.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Mercaptopurine can harm your liver, especially if you also use certain medicines for infections, tuberculosis, depression, birth control, hormone replacement, high cholesterol, heart problems, high blood pressure, seizures, pain, or arthritis (including Tylenol, Advil, Motrin, or Aleve).

Tell your doctor about all your other medicines, especially:

• allopurinol;

• olsalazine, mesalazine, sulfasalazine or similar medicines;

• sulfamethoxazole and trimethoprim; or

• warfarin (Coumadin, Jantoven).

This list is not complete. Other drugs may affect mercaptopurine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to mercaptopurine.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.