mercaptopurine

n.
A purine analogue, C₅H₄N₄S, that acts as an antimetabolite by interfering with purine synthesis, used primarily in the treatment of acute leukemia.

Key Terms: Consolidation therapy, Inflammatory bowel disease, Leukemia.

Definition

Mercaptopurine is a medicine used to prevent the formation and spread of cancer cells. Mercaptopurine is also called 6-mercaptopurine or 6-MP, and is available under the brand name Purinethol.

Purpose

Mercaptopurine is used as part of the consolidation and maintenance treatment for acute lymphocytic leukemia (ALL) and acute myelocytic leukemia (AML).

Description

Mercaptopurine is an analog of purine, a component of DNA/RNA, and belongs to antimetabolites that prevent the biosynthesis, or utilization, of normal cellular metabolites. It has been used for several decades in combination with other chemotherapy drugs for the treatment of different types of acute adult and childhood leukemias (ALL and AML). It has also been shown to be effective for the treatment of inflammatory bowel disease (IBD) (which includes Crohn's disease and ulcerative colitis), certain types of arthritis, and polycythemia vera (above normal increase in red cells in the blood). Mercaptopurine helps to decrease the dose of steroids in patients with IBD, and to reduce their dependence on steroids to control symptoms of their disease. The medicine is taken up by red cells in the blood and works by decreasing the formation of certain genetic material (DNA and RNA) in patients with cancer and by altering the activity of the immune system in patients with IBD.

Recommended Dosage

Doses vary between different chemotherapy protocols. The usual dose is 2.5 mg per kg (2.2 pounds) per day in adults and children (50 mg daily in an average 5-year old child or 100–200 mg daily in adults). The total daily dose is calculated to the nearest multiple of 25 mg and is given all at one time. Another way of dosing 6-MP is based on body surface area (BSA), and is usually 75 mg per square meter in children and 80–100 mg per square meter in adults.

Doses of 1.5–2.5 mg per kg per day is recommended for leukemia patients. For those patients with inflammatory bowel disease, doses of 1.5 mg per kg per day have been used in research studies.

Administration

This medicine is usually taken by mouth and should be given at the same time every day, preferably on an empty stomach (one hour before meals or two hours after meals). Children with leukemia should be taking this medicine at bedtime for maximum effectiveness. All patients should drink plenty of fluids (at least eight glasses of water per day) while taking this medication, unless otherwise directed by a physician.

Precautions

The use of 6-MP in pregnant women should be avoided whenever possible, especially during the first three months of pregnancy, as 6-MP can cause birth defects and spontaneous abortions.

As 6-MP can lower the body's ability to fight infections, patients are advised to avoid contact with people who have a cold, flu, or other infections.

Mercaptopurine should be used with caution in the following populations:

• people who had an allergic reaction to 6-MP in the past
• people at risk for pancreatitis (inflammation of the pancreas)
• breastfeeding mothers (it is not known if 6-MP crosses in to breast milk)
• people with liver or kidney disease
• people with gout (6-MP can exacerbate the symptoms of gout)
• people taking allopurinol for gout
• people with suppressed bone marrow (tissue filling the empty spaces inside the bone)

Patients are encouraged to stop taking 6-MP, and contact a physician immediately, if any of the following symptoms develop:

• fever, chills, or sore throat
• yellowing of the skin or eyes
• blood in the urine or stools
• black stools
• unusual bleeding or bruising
• stomach pain with nausea, vomiting, or loss of appetite

Patients taking 6-MP must see a physician before starting medication therapy, and also occasionally during therapy, to have blood tests for the monitoring of a complete blood count and kidney and liver functions.

Side Effects

This is a very potent medicine that can cause serious side effects. These side effects include skin rash, nausea, vomiting, diarrhea, mouth sores, yellowing of the eyes or skin, clay-colored stools, dark urine, decreased ability to fight infections, pinpoint red dots on the skin, and darkening of the skin. Nausea and vomiting, diarrhea, and stomach pain are less common in children than in adults.

Interactions

Mercaptopurine can decrease the effectiveness of blood thinners such as warfarin (Coumadin).

The drug can exacerbate the symptoms of gout. The anti-gout medication, allopurinol, can increase blood levels of 6-MP and increase the risk of its side effects. The dose of 6-MP needs to be decreased, or its use should be avoided, in patients taking allopurinol, which interferes with the degradation of 6-MP.

Risk of liver disease may be increased in patients taking both doxorubicin (a cancer chemotherapy drug) and 6-MP. Other medicines that decrease the function of the liver can cause increased toxicity with 6-MP. Patients should inform their doctor or pharmacist about all the prescription drugs and over-the-counter medications that they are taking.

—Olga Bessmertny, Pharm.D.

n
6-MP

trade name: Purinethol; drug class: antineoplastic-antimetabolite; action: inhibits purine metabolism at multiple sites, which inhibits DNA and RNA synthesis; uses: chronic myelocytic leukemia, acute lymphoblastic leukemia in children, acute myelogenous leukemia.

Brand names: Purinethol®

Chemical formula:

Español:
• Mercaptopurina, Tableta oral

Mercaptopurine Oral tablet

What is this medicine?

MERCAPTOPURINE, 6-MP is a chemotherapy drug. It interferes with the growth of cancer cells and can reduce immune system activity. It is used to treat certain types of acute leukemia. It is occasionally used for other medical conditions.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
• infection (especially virus infection such as chickenpox or herpes)
• kidney disease
• liver disease
• low blood counts like low platelets, red blood cells, or white blood cells
• thiopurine methyltransferase (TPMT) deficiency
• an unusual or allergic reaction to mercaptopurine, azathioprine, other chemotherapy, other medicines, foods, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding

How should I use this medicine?

Take this medicine by mouth with a glass of water. Follow the directions on the prescription label. Take your medicine at regular intervals. Do not take it more often than directed. Do not stop taking except on your doctor's advice.

Talk to your pediatrician regarding the use of this medicine in children. While this drug may be prescribed for selected conditions, precautions do apply.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.
NOTE: This medicine is only for you. Do not share this medicine with others.

What may interact with this medicine?

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

This medicine may also interact with the following medications:
• allopurinol
• balsalazide
• medicines to increase blood counts like filgrastim, pegfilgrastim, sargramostim
• other chemotherapy drugs like doxorubicin
• mesalazine, 5-ASA
• olsalazine
• sulfasalazine
• vaccines
• warfarin

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

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.

To protect your kidneys, drink water or other fluids as directed while you are taking this medicine.

In some cases, you may be given additional medicines to help with side effects. Follow all directions for their use.

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.

Be careful brushing and flossing your teeth or using a toothpick because you may get an infection or bleed more easily. If you have any dental work done, tell your dentist you are receiving this medicine.

Avoid taking products that contain aspirin, acetaminophen, ibuprofen, naproxen, or ketoprofen unless instructed by your doctor. These medicines may hide a fever.

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.

Men should inform their doctors if they wish to father a child. This medicine may lower sperm counts.

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
• 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 infection - fever or chills, cough, sore throat, pain or difficulty passing urine
• 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, fainting spells, lightheadedness
• breathing problems
• confusion
• mouth soreness or patches
• nausea, vomiting
• right upper belly pain
• swelling of the ankles, feet, hands, or stomach
• trouble passing urine or change in the amount of urine
• yellowing of the eyes or skin

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):
• darkening of the skin
• diarrhea
• hair loss
• loss of appetite

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medicine?

Keep out of the reach of children.

Store at room temperature between 15 and 25 degrees C (59 and 77 degrees F). Protect from moisture. Keep container tightly closed. Throw away any unused medicine after the expiration date.

Last updated: 7/1/2002

Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.

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