MERCAPTOPURINE (Systemic)

Some commonly used brand names are:

In the U.S.?

• Purinethol

In Canada?

• Purinethol

Another commonly used name is 6-MP.

Category

• Antineoplastic
• Immunosuppressant

Description

Mercaptopurine (mer-kap-toe-PYOOR-een) belongs to the group of medicines known as antimetabolites.It is used to treat some kinds of cancer.

Mercaptopurine interferes with the growth of cancer cells, which are eventuallydestroyed. Since the growth of normal body cells may also be affected by mercaptopurine,other effects will also occur. Some of these may be serious and must be reportedto your doctor. Other effects may not be serious but may cause concern. Someeffects may not occur for months or years after the medicine is used.

Before you begin treatment with mercaptopurine, you and your doctor shouldtalk about the good this medicine will do as well as the risks of using it.

Mercaptopurine may also be used for other conditions as determined by yourdoctor.

Mercaptopurine is available only with your doctor's prescription, in thefollowing dosage form:

Oral
• Tablets (U.S. and Canada)

Before Using This Medicine

In deciding to use a medicine,the risks of taking the medicine must be weighed against the good it willdo. This is a decision you and your doctor will make. For mercaptopurine,the following should be considered:

Allergies?Tell your doctor if you have ever had any unusual orallergic reaction to mercaptopurine.

Pregnancy?Tell your doctor if you are pregnant or if you intendto have children. There is a chance that this medicine may cause birth defectsif either the male or female is taking it at the time of conception or ifit is taken during pregnancy. However, studies have not been done in humans.Mercaptopurine has been shown to cause damage to the fetus in rats and increasesthe risk of miscarriage or premature births in humans. In addition, many cancermedicines may cause sterility which could be permanent. Although this hasnot been reported with this medicine, the possibility should be kept in mind.

Be sure that you have discussed this with your doctor before taking thismedicine. It is best to use some kind of birth control while you are takingmercaptopurine. Tell your doctor right away if you think you have become pregnantwhile taking mercaptopurine.

Breast-feeding?Tell your doctor if you are breast-feeding or ifyou intend to breast-feed during treatment with this medicine. Because mercaptopurinemay cause serious side effects, breast-feeding is generally not recommendedwhile you are taking it.

Children?Although there is no specific information comparinguse of mercaptopurine in children with use in other age groups, it is notexpected to cause different side effects or problems in children than it doesin adults.

Older adults?Many medicines have not been studied specificallyin older people. Therefore, it may not be known whether they work exactlythe same way they do in younger adults or if they cause different side effectsor problems in older people. There is no specific information comparing useof mercaptopurine in the elderly with use in other age groups.

Other medicines?Although certain medicines should not be usedtogether at all, in other cases two different medicines may be used togethereven if an interaction might occur. In these cases, your doctor may want tochange the dose, or other precautions may be necessary. When you are takingmercaptopurine, it is especially important that your health care professionalknow if you are taking any of the following:

• Acetaminophen (e.g., Tylenol) (with long-term, high-dose use) or
• Amiodarone (e.g., Cordarone) or
• Anabolic steroids (nandrolone [e.g., Anabolin], oxandrolone [e.g.,Anavar], oxymetholone [e.g., Anadrol], stanozolol [e.g., Winstrol]) or
• Androgens (male hormones) or
• Anti-infectives by mouth or by injection (medicine for infection)or
• Antithyroid agents (medicine for overactive thyroid) or
• Carbamazepine (e.g., Tegretol) or
• Chloroquine (e.g., Aralen) or
• Dantrolene (e.g., Dantrium) or
• Disulfiram (e.g., Antabuse) or
• Divalproex (e.g., Depakote) or
• Estrogens (female hormones) or
• Etretinate (e.g., Tegison) or
• Gold salts (medicine for arthritis) or
• Hydroxychloroquine (e.g., Plaquenil) or
• Methyldopa (e.g., Aldomet) or
• Naltrexone (e.g., Trexan) (with long-term, high-dose use) or
• Oral contraceptives (birth control pills) containing estrogen or
• Phenothiazines (acetophenazine [e.g., Tindal], chlorpromazine [e.g.,Thorazine], fluphenazine [e.g., Prolixin], mesoridazine [e.g., Serentil],perphenazine [e.g., Trilafon], prochlorperazine [e.g., Compazine], promazine[e.g., Sparine], promethazine [e.g., Phenergan], thioridazine [e.g., Mellaril],trifluoperazine [e.g., Stelazine], triflupromazine [e.g., Vesprin], trimeprazine[e.g., Temaril]) or
• Phenytoin (e.g., Dilantin) or
• Plicamycin (e.g., Mithracin) or
• Valproic acid (e.g., Depakene)?Risk of unwanted effects onthe liver may be increased

• Azathioprine (e.g., Imuran) or
• Corticosteroids (cortisone-like medicine) or
• Cyclosporine (e.g., Sandimmune) or
• Muromonab-CD3 (monoclonal antibody) (e.g., Orthoclone OKT3)?Theremay be an increased risk of infection and development of cancer because mercaptopurinereduces the body's immunity

• Allopurinol (e.g., Zyloprim)?Effects of mercaptopurine maybe increased because allopurinol blocks its removal from the body

• Amphotericin B by injection (e.g., Fungizone) or
• Antithyroid agents (medicine for overactive thyroid) or
• Azathioprine (e.g., Imuran) or
• Chloramphenicol (e.g., Chloromycetin) or
• Colchicine or
• Flucytosine (e.g., Ancobon) or
• Ganciclovir (e.g., Cytovene) or
• Interferon (e.g., Intron A, Roferon-A) or
• Plicamycin (e.g., Mithracin) or
• Zidovudine (e.g., AZT, Retrovir) or
• If you have ever been treated with radiation or cancer medicines?Mercaptopurinemay increase the effects of these medicines or radiation therapy on the blood

• Probenecid (e.g., Benemid) or
• Sulfinpyrazone (e.g., Anturane)?Mercaptopurine may raise theconcentration of uric acid in the blood. Since these medicines are used tolower uric acid levels, they may not be as effective in patients taking mercaptopurine

Other medical problems?The presence of other medicalproblems may affect the use of mercaptopurine. Make sure you tell your doctorif you have any other medical problems, especially:

• Chickenpox (including recent exposure) or
• Herpes zoster (shingles)?Risk of severe disease affecting otherparts of the body

• Gout (history of) or
• Kidney stones (history of)?Mercaptopurine may increase levelsof uric acid in the body, which can cause gout or kidney stones

• Infection?Mercaptopurine may decrease your body's ability tofight infection

• Kidney disease or
• Liver disease?Effects of mercaptopurine may be increased becauseof slower removal from the body

Proper Use of This Medicine

Use this medicine only as directed by your doctor. Do not use moreor less of it, and do not use it more often than your doctor ordered. Theexact amount of medicine you need has been carefully worked out. Taking toomuch may increase the chance of side effects, while taking too little maynot improve your condition.

Mercaptopurine is often given together with certain other medicines. Ifyou are using a combination of medicines, make sure that you take each oneat the right time and do not mix them. Ask your health care professional tohelp you plan a way to remember to take your medicines at the right times.

While you are using mercaptopurine, your doctor may want you to drink extrafluids so that you will pass more urine. This will help prevent kidney problemsand keep your kidneys working well.

If you vomit shortly after taking a dose of mercaptopurine, check withyour doctor. You will be told whether to take the dose again or to wait untilthe next scheduled dose.

Dosing?The dose of mercaptopurine will be differentfor different patients. The dose that is used may depend on a number of things,including what the medicine is being used for, the patient's weight, and whetheror not other medicines are also being taken. If you aretaking mercaptopurine at home, follow your doctor's orders or the directionson the label. If you have any questions about the proper dose of mercaptopurine,ask your doctor.

Missed dose?If you miss a dose of this medicine, do not takethe missed dose at all and do not double the next one. Instead, go back toyour regular dosing schedule and check with your doctor.

Storage?To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in otherdamp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be surethat any discarded medicine is out of the reach of children.

Precautions While Using This Medicine

It is very important that your doctor check your progress atregular visits to make sure that this medicine is working properlyand to check for unwanted effects.

Avoid alcoholic beverages until you have discussedtheir use with your doctor. Alcohol may increase the harmful effectsof this medicine.

While you are being treated with mercaptopurine, and after you stop treatmentwith it, do not have any immunizations (vaccinations)without your doctor's approval. Mercaptopurine may lower your body'sresistance and there is a chance you might get the infection the immunizationis meant to prevent. In addition, other persons living in your household shouldnot take oral polio vaccine since there is a chance they could pass the poliovirus on to you. Also, avoid persons who have taken oral polio vaccine. Donot get close to them and do not stay in the same room with them for verylong. If you cannot take these precautions, you should consider wearing aprotective face mask that covers the nose and mouth.

Mercaptopurine can temporarily lower the number of white blood cells inyour blood, increasing the chance of getting an infection. It can also lowerthe number of platelets, which are necessary for proper blood clotting. Ifthis occurs, there are certain precautions you can take, especially when yourblood count is low, to reduce the risk of infection or bleeding:

• If you can, avoid people with infections. Checkwith your doctor immediately if you think you are getting an infectionor if you get a fever or chills, cough or hoarseness, lower back or side pain,or painful or difficult urination.
• Check with your doctor immediately ifyou notice any unusual bleeding or bruising; black, tarry stools; blood inurine or stools; or pinpoint red spots on your skin.
• Be careful when using a regular toothbrush, dental floss, or toothpick.Your medical doctor, dentist, or nurse may recommend other ways to clean yourteeth and gums. Check with your medical doctor before having any dental workdone.
• Do not touch your eyes or the inside of your nose unless you havejust washed your hands and have not touched anything else in the meantime.
• Be careful not to cut yourself when you are using sharp objects suchas a safety razor or fingernail or toenail cutters.
• Avoid contact sports or other situations where bruising or injurycould occur.

Tell the doctor in charge that you are taking this medicine before youhave any medical tests. The results of tests for the amount of sugar or uricacid in the blood measured by a machine called a sequential multiple analyzer(SMA) may be affected by this medicine.

Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects.Although not all of these side effects may occur, if they do occur they mayneed medical attention.

Also, because of the way cancer medicines act on the body, there is a chancethat they might cause other unwanted effects that may not occur until monthsor years after the medicine is used. These delayed effects may include certaintypes of cancer. Discuss these possible effects with your doctor.

Check with your doctorimmediately if any of the following side effects occur:

Less common

Black, tarry stools; blood in urineor stools; cough or hoarseness; fever or chills; lower back or side pain; painful or difficult urination; pinpointred spots on skin; unusual bleeding or bruising

Check withyour doctor as soon as possible if any of the following side effects occur:

More common

Unusual tiredness or weakness; yelloweyes or skin

Less common

Joint pain; loss of appetite; nausea and vomiting; swelling of feetor lower legs

Rare

Sores in mouth and on lips

Other side effects may occurthat usually do not need medical attention. These side effects may go awayduring treatment as your body adjusts to the medicine. Also, your health careprofessional may be able to tell you about ways to prevent or reduce someof these side effects. Check with your health care professional if any ofthe following side effects continue or are bothersome or if you have any questionsabout them:

Less common

Darkening of skin; diarrhea; headache; skin rash and itching; weakness

After you stop taking mercaptopurine, it may still produce someside effects that need attention. During this period of time, check with yourdoctor if you notice any of the following side effects:

Black, tarry stools; blood in urineor stools; cough or hoarseness; fever or chills; lower back or side pain; painful or difficult urination; pinpointred spots on skin; unusual bleeding or bruising; yellow eyes or skin

Other sideeffects not listed above may also occur in some patients. If you notice anyother effects, check with your doctor.