Purinethol (mercaptopurine) is used to treat a certain type of cancer (acute lymphocytic leukemia). It is a chemotherapy drug that works by slowing or stopping the growth of cancer cells.

Talk to the doctor about the risks and benefits of mercaptopurine, especially when used in children and young adults. It may be given to you for other reasons. Talk with the doctor.

Use Purinethol (mercaptopurine tablets) as ordered by your doctor. Read all information given to you. Follow all instructions closely.

Take Purinethol (mercaptopurine tablets) at the same time of day.

Talk with your doctor or pharmacist about how to take Purinethol (mercaptopurine tablets) with regard to food.

Drink lots of noncaffeine liquids unless told to drink less liquid by your doctor.

Your doctor will tell you how to take Purinethol (mercaptopurine tablets). Be sure you know how much to take, how often to take Purinethol (mercaptopurine tablets), and how to store this drug. If your doctor does not tell you how to use Purinethol (mercaptopurine tablets) or if you are not sure how to use it, talk with your doctor.

You will need to take special care when handling Purinethol (mercaptopurine tablets). Check with the doctor or pharmacist to see how to handle Purinethol (mercaptopurine tablets).

What do I need to tell my doctor BEFORE I take Purinethol?

• If you have an allergy to mercaptopurine or any other part of Purinethol (mercaptopurine tablets).
• If you are allergic to any drugs like this one, any other drugs, foods, or other substances. Tell your doctor about the allergy and what signs you had, like rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
• If you have taken Purinethol (mercaptopurine tablets) or a drug called thioguanine before and your cancer did not respond.
• If you are taking allopurinol.
• If you are breast-feeding or plan to breast-feed.

This is not a list of all drugs or health problems that interact with Purinethol (mercaptopurine tablets).

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Purinethol (mercaptopurine tablets) with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take Purinethol?

Tell all of your health care providers that you take Purinethol (mercaptopurine tablets). This includes your doctors, nurses, pharmacists, and dentists.

If you have upset stomach, throwing up, diarrhea, or are not hungry, talk with your doctor. There may be ways to lower these side effects.

Very bad and sometimes life-threatening blood and bone marrow problems like anemia, low platelet counts, or low white blood cell counts have happened with Purinethol (mercaptopurine tablets). Change in dose or even stopping the drug may be needed if any of these side effects happen. Talk with the doctor.

You may have more chance of getting an infection. Wash hands often. Stay away from people with infections, colds, or flu.

You may bleed more easily. Be careful and avoid injury. Use a soft toothbrush and an electric razor.

If you have thiopurine S-methyltransferase (TPMT) or nucleotide diphosphatase (NUDT15) deficiency, talk with your doctor.

This medicine may add to the chance of getting some types of cancer. Talk with the doctor.

A rare type of cancer called hepatosplenic T-cell lymphoma (HSTCL) has happened with Purinethol (mercaptopurine tablets). These cases have been deadly. Most of the time, these cases happened in teenagers or young adults. Most of these patients were using Purinethol (mercaptopurine tablets) to treat certain types of bowel problems like Crohn disease and ulcerative colitis. This medicine is not approved for use to treat bowel problems like these. Tell the doctor if you have ever had any type of cancer. Talk with the doctor.

Have blood work checked as you have been told by the doctor. Talk with the doctor.

If you are taking warfarin, talk with your doctor. You may need to have your blood work checked more closely while you are taking it with Purinethol (mercaptopurine tablets).

Talk with your doctor before getting any vaccines. Use of some vaccines with Purinethol (mercaptopurine tablets) may either raise the chance of an infection or make the vaccine not work as well.

You may get sunburned more easily. Avoid sun, sunlamps, and tanning beds. Use sunscreen and wear clothing and eyewear that protects you from the sun.

A very bad and sometimes life-threatening problem called Macrophage Activation Syndrome (MAS) may rarely happen in people with autoimmune diseases. Talk with the doctor.

Low blood sugar has happened in people taking Purinethol (mercaptopurine tablets), especially children. Signs may be dizziness, headache, feeling sleepy, feeling weak, shaking, a fast heartbeat, confusion, hunger, or sweating. Call your doctor right away if you have any of these signs.

This medicine may cause harm to the unborn baby or loss of the unborn baby if you take it while you are pregnant.

Use birth control that you can trust to prevent pregnancy while taking Purinethol (mercaptopurine tablets). If you are pregnant or you get pregnant while taking Purinethol (mercaptopurine tablets), call your doctor right away.

Nausea, vomiting, diarrhea, and loss of appetite may occur. Temporary hair loss may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

People using this medication may have serious side effects. However, your doctor has prescribed this drug because he or she has judged that the benefit to you is greater than the risk of side effects. Careful monitoring by your doctor may decrease your risk.

Tell your doctor right away if you have any serious side effects, including: joint pain/swelling, black stools, vomit that looks like coffee grounds, signs of kidney problems (such as change in the amount of urine, pain in the lower back/side).

Get medical help right away if you have any very serious side effects, including: symptoms of liver disease (such as nausea/vomiting that doesn't stop, stomach/abdominal pain, yellowing eyes/skin, dark urine).

This medication may decrease bone marrow function, an effect that may lead to a low number of blood cells such as red cells, white cells, and platelets. This effect can cause anemia, decrease your body's ability to fight an infection, or cause easy bruising/bleeding. Tell your doctor right away if you develop any of the following symptoms: unusual tiredness, pale skin, signs of infection (such as sore throat that doesn't go away, fever, chills), easy bruising/bleeding.

Mercaptopurine may rarely increase your risk of developing certain types of cancer (such as lymphoma, skin, cervical). This risk is higher in children/young adults being treated for certain bowel diseases (such as Crohn's disease, ulcerative colitis). Keep all medical and laboratory appointments. Tell your doctor right away if you develop any of the following symptoms: swollen abdomen, swollen lymph nodes, night sweats, unexplained weight loss, unusual skin changes (such as new skin lesion or bump, or change in size or color of a mole), unusual vaginal bleeding/discharge.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

What may interact with this medicine?

Do not take this medicine with any of the following medications:

• febuxostat

This medicine may also interact with the following medications:

• allopurinol
• certain medicines that treat or prevent blood clots like warfarin
• certain medicines that treat ulcerative colitis like balsalazide, olsalazine, mesalamine, or sulfasalazine
• live virus vaccines
• trimethoprim-sulfamethoxazole

What should I watch for while using this medicine?

This drug may make you feel generally unwell. This is not uncommon, as chemotherapy can affect healthy cells as well as cancer cells. Report any side effects. Continue your course of treatment even though you feel ill unless your doctor tells you to stop.

Call your doctor or health care professional for advice if you get a fever, chills or sore throat, or other symptoms of a cold or flu. Do not treat yourself. This drug decreases your body's ability to fight infections. Try to avoid being around people who are sick.

This medicine may increase your risk to bruise or bleed. Call your doctor or health care professional if you notice any unusual bleeding.

This medicine can make you more sensitive to the sun. Keep out of the sun. If you cannot avoid being in the sun, wear protective clothing and use sunscreen. Do not use sun lamps or tanning beds/booths.

Talk to your doctor about your risk of cancer. You may be more at risk for certain types of cancers if you take this medicine.

Do not become pregnant while taking this medicine. Women should inform their doctor if they wish to become pregnant or think they might be pregnant. There is a potential for serious side effects to an unborn child. Talk to your health care professional or pharmacist for more information. Do not breast-feed an infant while taking this medicine.

This medicine has caused reduced sperm counts in some men. This may interfere with the ability to father a child. You should talk to your doctor or health care professional if you are concerned about your fertility.

What side effects may I notice from receiving this medicine?

Side effects that you should report to your doctor or health care professional as soon as possible:

• allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
• breathing problems
• low blood counts - this medicine may decrease the number of white blood cells, red blood cells and platelets. You may be at increased risk for infections and bleeding
• signs of decreased platelets or bleeding - bruising, pinpoint red spots on the skin, black, tarry stools, blood in the urine
• signs of decreased red blood cells - unusually weak or tired, feeling faint or lightheaded, falls
• signs of infection - fever or chills, cough, sore throat, pain or difficulty passing urine
• signs and symptoms of liver injury like dark yellow or brown urine; general ill feeling or flu-like symptoms; light-colored stools; loss of appetite; nausea; right upper belly pain; unusually weak or tired; yellowing of the eyes or skin
• sore throat
• swelling of the stomach

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):

• diarrhea
• hair loss
• mouth sores
• vomiting