Class: Chemotherapy

Generic Name: Mercaptopurine (mer-kap-toe-PYOOR-een), 6-Mercaptopurine, 6-MP
Trade Name: Purinethol®

How is this drug used? Mercaptopurine is FDA approved for the treatment of acute lymphatic leukemia.  It is important for patients to remember that physicians have the ability to prescribe medication for conditions other than those for which the drug has been approved by the FDA. Patients who have received a prescription of this drug for a condition other than which it is approved may wish to discuss this issue with their physician.

What is the mechanism of action? Mercaptopurine belongs to a group of drugs classified as antimetabolites.  Antimetabolites produce their anti-cancer effects by inhibiting the ability of a cell to produce or repair DNA and RNA, thereby making the cell unable to replicate or repair itself and ultimately causing cellular death.

How is mercaptopurine given (administered)? Mercaptopurine is given orally in a tablet and the dose depends on several factors, including the condition being treated, the size of the patient, the particular regimen being used and the overall health of the patient.

How are patients monitored? Patients will usually have scheduled meetings with their healthcare provider while they are being treated with mercaptopurine.  Patients may undergo physical examinations, scans, or other measures to assess side effects and response to therapy. Typically, blood will be drawn to check levels of blood cells and to monitor functions of some organ systems, particularly the liver as mercaptopurine can cause liver damage.

Patients will be closely monitored for liver abnormalities. In addition evaluating blood samples to determine liver function, patients will be checked for yellowing of the skin or eyes tenderness or pain in the right upper quadrant of the abdomen, diarrhea, inability to eat/weight loss and abdominal swelling. If patients experience any of these symptoms, they should contact their healthcare provider.

In addition, some patients will be at an increased risk for developing a condition called tumor lysis syndrome in which electrolyte and metabolic disturbances occur.  Tumor lysis syndrome can be prevented if managed aggressively at the beginning of treatment.  Blood tests will measure levels of electrolyte and metabolic products, and patients should contact their healthcare provider if they experience symptoms such as nausea and vomiting, shortness of breath, an irregular heartbeat, clouding of urine, lethargy and/or joint discomfort.  Patients may be given medication to prevent this condition.

What are the common (occur in 30% or more of patients) side effects of treatment with mercaptopurine?

• Low white blood cell levels – increases the risk of infection
• Low red blood cell levels – increases the risk of anemia
• Low platelet levels – increases the risk of bleeding
• Abnormalities in liver function tests as determined by blood tests, liver damage, jaundice

What are the less common (occur in 10% to 29% of patients) side effects of treatment with mercaptopurine?

• Nausea and vomiting
• Loss of appetite
• Infertility

This is not a complete list of side effects. Some patients may experience other side effects that are not listed here. Patients may wish to discuss with their physician the other less common side effects of this drug, some of which may be serious.

Some side effects may require medical attention. Other side effects do not require medical attention and may go away during treatment. Patients should check with their physician about any side effects that continue or are bothersome.

What can patients do to help alleviate or prevent discomfort and side effects?

• Pay careful attention to the physician’s instructions and inform the physician of any side effects.
• Maintain adequate rest and nutrition.
• Wear sunscreen and protective clothing and try to minimize sun exposure.
• Drink plenty of fluids. (Patients should ask their physician about the amount of liquid to consume during a day.)
• If possible, avoid large crowds or people who are sick or not feeling well, as this drug may leave some patients susceptible to infection.
• Wash hands often to reduce the risk of infection.
• Eat small meals frequently to help alleviate nausea.
• If patients have been prescribed an anti-nausea medication, they should be sure to take the prescribed doses.
• Avoid activities that may cause injury or bruising.
• Use a soft toothbrush and an electric razor to prevent cuts on the mouth or skin.
• For mouth sores, patients should rinse their mouth three times a day with a salt and soda solution (8 ounces of water mixed with ½ to 1 tsp baking soda and/or ½ to 1 tsp salt) and brush their teeth with a soft toothbrush to help prevent the development of mouth sores.

Are there any special precautions patients should be aware of before starting treatment?

• Patients should inform their physician if they are pregnant, breastfeeding or planning a family in the near future. This drug may cause birth defects. It is important to use some kind of birth control while undergoing treatment. Also, patients may want to talk to their physician if they are considering having children in the future, since some drugs may cause fertility problems.
• It is important that patients inform their physician of any pre-existing conditions (chicken pox, heart disease, kidney disease, liver disease, lung disease, etc.) as they may worsen with this drug.
• Patients should inform their physician of any other medication they are taking (whether prescription or over-the-counter, including vitamins, herbs, etc.) as they may interfere with treatment.
• Patients should inform their physician if taking the blood thinner, warfarin, as they may require additional monitoring.
• Patients should check with their physician before starting any new drug or nutritional supplement.
• Patients should inform their physician of any known drug or food allergies or any reactions to medications they have experienced in the past.
• Patients should keep medication out of reach of children and return any unused drug to a pharmacy.
• Follow all prescribing instruction.

When should patients notify their physician?

• Mouth sores
• Signs of liver abnormalities – yellowing of skin or eyes, right upper quadrant tenderness or pain, diarrhea, inability to eat/weight loss, abdominal swelling
• Flu or cold-like symptoms – fever, sore throat, cough, chills
• Signs of infection – redness, swelling, pus, tenderness, painful urination
• Unexplained or excessive bleeding (nosebleeds, bruising, black tarry stools, blood in the urine, etc.)
• Persistent or severe fatigue
• Difficulty breathing
• Unusual weight gain
• Swelling of extremities
• Skin rash, hives or itching

What is a package insert?
A package insert is required by the FDA and contains a summary of the essential scientific information needed for the safe and effective use of the drug for healthcare providers and consumers.  A package insert typically includes information regarding specific indications, administration schedules, dosing, side effects, contraindications, results from some clinical trials, chemical structure, pharmacokinetics and metabolism of the specific drug. By carefully reviewing the package insert, you will get the most complete and current information about how to safely use this drug. If you do not have the package insert for the drug you are using, your pharmacist or physician may be able to provide you with a copy.

Copyright © 2010 CancerConnect Last updated 07/10.

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