Purinethol (Oral)

Mercaptopurine is used along with other medicines to maintain treatment for acute lymphoblastic leukemia. It is part of a group of medicines called antimetabolites.

Mercaptopurine works by interfering with the growth of cancer cells, leading to their destruction. However, it can also affect the growth of normal cells, which may cause other unwanted effects. Some of these effects can be serious and should be reported to your doctor.

This medicine is only available with a prescription from your doctor.

It is very important that your doctor checks your progress during regular visits to ensure that this medicine is working properly. Blood tests may be necessary to look for unwanted effects. Genetic testing may also be done to check your levels of thiopurine S-methyltransferase (an enzyme needed to metabolize mercaptopurine).

Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to prevent pregnancy during treatment with this medicine and for at least 6 months after your last dose. Male patients with female partners should also use effective birth control during treatment with this medicine and for at least 3 months after the last dose. If you think you have become pregnant while using this medicine, tell your doctor right away.

Mercaptopurine can temporarily lower the number of white blood cells in your blood, increasing the risk of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this happens, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

• If possible, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you develop a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
• Check with your doctor immediately if you notice any unusual bleeding or bruising, black, tarry stools, blood in the urine 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 suggest other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
• Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
• Be cautious when using sharp objects such as a safety razor or fingernail or toenail cutters to avoid cutting yourself.
• Avoid contact sports or situations where bruising or injury could happen.

Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin. These could be signs of a serious liver problem.

While you are being treated with mercaptopurine, and after you stop treatment with it, do not have any immunizations (vaccines) without your doctor's approval. Mercaptopurine may weaken your body's resistance, and the vaccine may not work as well or you might get the infection that the vaccine is meant to prevent. Additionally, you should not be around people in your household who receive live virus vaccines because they could pass the virus on to you. Some examples of live vaccines include measles, mumps, influenza (nasal flu vaccine), poliovirus (oral form), rotavirus, and rubella. Avoid close contact with them and do not stay in the same room with them for long. If you have questions about this, talk to your doctor.

This medicine may increase your risk of getting certain types of cancer, including skin cancer and cervical cancer. Some teenagers and young adults with Crohn's disease or ulcerative colitis have developed a rare type of cancer called hepatosplenic T-cell lymphoma (HSTCL). Check with your doctor right away if you have unusual bleeding, bruising, or weakness, swollen lymph nodes in the neck, underarms, or groin, or unexplained weight loss.

This medicine may cause a life-threatening condition called macrophage activation syndrome (MAS). This usually occurs in patients with an autoimmune disease (e.g., inflammatory bowel disease) or a virus infection (e.g., Epstein-Barr, cytomegalovirus) and must be treated immediately. Tell your doctor right away if you have a fever, a persistent cough, redness in one part of your body, or warmth or swelling of your skin.

Talk with your doctor before using this medicine if you plan to have children. Some men and women using this medicine have become infertile (unable to have children).

This medicine may make your skin more sensitive to sunlight. Wear sunscreen. Do not use sunlamps or tanning beds.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

In deciding to use a medicine, the risks of taking the medicine must be weighed against the benefits it will provide. This is a decision you and your doctor will make together. For this medicine, consider the following:

Allergies

Inform your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also, let your healthcare professional know if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies have not been conducted on how age affects the effects of mercaptopurine in children. Safety and effectiveness have not been established. The oral liquid may cause hypoglycemia (low blood sugar) in children younger than 6 years of age or those with a low body mass index.

Geriatric

Current studies have not shown specific problems in the elderly that would limit the usefulness of mercaptopurine. However, older patients are more likely to have age-related liver, kidney, or heart issues, which may require caution and a dose adjustment for those taking mercaptopurine.

Breast Feeding

There are no adequate studies in women to determine the risk to infants when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Interactions with Medicines

Some medicines should not be used together at all, while in other cases, two different medicines may be used together even if an interaction could happen. In these situations, your doctor may want to adjust the dose, or other precautions may be necessary. When taking this medicine, it is especially important for your healthcare professional to know if you are taking any of the medicines listed below. The following interactions have been chosen based on their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

• Febuxostat
• Measles Virus Vaccine, Live
• Mumps Virus Vaccine, Live
• Rotavirus Vaccine, Live
• Rubella Virus Vaccine, Live
• Varicella Virus Vaccine, Live
• Zoster Vaccine, Live

Using this medicine with any of the following medicines is usually not recommended, but may be necessary in some cases. If both medicines are prescribed together, your doctor may adjust the dose or how often you use one or both of the medicines.

• Adenovirus Vaccine
• Alacepril
• Alfalfa
• Allopurinol
• Azathioprine
• Bacillus of Calmette and Guerin Vaccine, Live
• Benazepril
• Black Cohosh
• Captopril
• Cholera Vaccine, Live
• Cilazapril
• Dengue Tetravalent Vaccine, Live
• Doxorubicin
• Doxorubicin Hydrochloride Liposome
• Enalaprilat
• Enalapril Maleate
• Fosinopril
• Influenza Virus Vaccine, Live
• Levoketoconazole
• Lisinopril
• Mesalamine
• Methotrexate
• Moexipril
• Mycophenolic Acid
• Olsalazine
• Oxypurinol
• Pentopril
• Perindopril
• Poliovirus Vaccine, Live
• Quinapril
• Ramipril
• Ribavirin
• Smallpox Vaccine
• Spirapril
• Sulfamethoxazole
• Sulfasalazine
• Trandolapril
• Trimethoprim
• Typhoid Vaccine, Live
• Warfarin
• Yellow Fever Vaccine
• Zofenopril

Using this medicine with any of the following medicines may increase the risk of certain side effects, but using both drugs might be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Acenocoumarol
• Cyclosporine
• Phenprocoumon

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be taken with food or certain types of food, as interactions may occur. Drinking alcohol or using tobacco with certain medicines may also cause interactions. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

Having other medical issues may affect the use of this medicine. Be sure to tell your doctor if you have any other medical problems, especially:

• Anemia or
• Blood or bone marrow problems or
• Bowel problems (e.g., nausea, vomiting, diarrhea) or
• Gout or
• Leukopenia (low white blood cells) or
• Liver disease or
• Thrombocytopenia (low platelets in the blood)—Use with caution. May worsen these conditions.

• Autoimmune disease (e.g., inflammatory bowel disease) or
• Viral infections (e.g., Epstein-Barr, cytomegalovirus)—Use with caution. May worsen side effects.

• Infection—May reduce your body's ability to fight infection.

• Kidney disease—Use with caution. The effects may be stronger because the medicine is removed from the body more slowly.

Along with its necessary effects, a medicine may cause some unwanted effects. Not all of these side effects may happen, but if they do, they might need medical attention.

Check with your doctor right away if any of the following side effects occur:

More common

• Black, tarry stools
• Bleeding gums
• Clay colored stools
• Cough or hoarseness
• Dark urine
• Decreased appetite
• Fever or chills
• Headache
• Loss of appetite
• Lower back or side pain
• Nausea, vomiting
• Painful or difficult urination
• Pale skin
• Pinpoint red spots on the skin
• Rash, itchy skin
• Stomach pain or tenderness
• Swelling of the feet or lower legs
• Trouble with breathing upon exertion
• Unusual bleeding or bruising
• Unusual tiredness or weakness
• Yellow eyes or skin

Less common

• Chest pain
• Joint pain
• Sore throat
• Sores, ulcers, or white spots on the lips or in the mouth
• Swollen glands

Incidence not known

• Anxiety
• Blurred vision
• Cold sweats
• Coma
• Confusion
• Constipation
• Depression
• Diarrhea
• Dizziness
• Fast heartbeat
• Heartburn
• Increased hunger
• Increased sensitivity of the skin to sunlight
• Indigestion
• Joint pain, stiffness, or swelling
• Nervousness
• Nightmares
• Redness or other discoloration of the skin
• Seizures
• Severe sunburn
• Shakiness
• Slurred speech
• Stomach cramping or burning
• Vomiting of blood or material that looks like coffee grounds

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to explain how to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

• Darkening of the skin

Incidence not known

• Hair loss or thinning of the hair
• Low sperm count

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

In the U.S.

• Purinethol
• Purixan

Available Dosage Forms:

• Suspension
• Tablet

Therapeutic Class: Antineoplastic Agent

Pharmacologic Class: Antimetabolite

Medicines used to treat cancer are very strong and can have many side effects. Before using this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.

Use this medicine exactly as directed by your doctor. Do not use more of it, do not use it more often, and do not use it for a longer time than your doctor ordered.

Mercaptopurine is given together with certain other medicines. If you are using a combination of medicines, it is important that you take each medicine at the right time. Follow your doctor's instructions on when to take these medicines.

Shake the oral liquid for at least 30 seconds to make sure that it is well mixed. Measure the dose with a marked measuring oral syringe and adaptor. Wash the dosing syringe with warm soapy water, rinse, and dry well after each use.

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

Tell your doctor if you are using this medicine together with allopurinol. Your doctor may decrease your dose of the oral liquid.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

• For oral dosage forms (suspension or tablets):For maintenance treatment of acute lymphatic leukemia: Adults—Dose is based on body weight and must be determined by your doctor. At first, 1.5 to 2.5 milligrams (mg) per kilogram (kg) of body weight per day, taken as a single dose. Your doctor may adjust your dose as needed and tolerated. Children—Use and dose must be determined by your doctor.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

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

Storage

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Once opened, use the oral liquid within 8 weeks. Throw away any unused medicine after 8 weeks.