Thioguanine

(thigh-oh-gwon-een)

Trade/other name(s): 6-TG, 6-Thioguanine, Tabloid

Why would this drug be used?

Thioguanine is used to treat some kinds of acute leukemia and other types of cancer.

How does this drug work?

Thioguanine belongs to a general group of chemotherapy drugs called anti-metabolites. It keeps cells from making DNA and RNA. This stops cancer cells from growing and they eventually die.

Before taking this medicine

Tell your doctor…

• If you are allergic to anything, including medicines, dyes, additives, or foods.
• If you have any medical conditions such as kidney disease, liver disease (including hepatitis), heart disease, congestive heart failure, diabetes, gout, infections, or if you have had kidney stones. These conditions may require that your medicine dose, regimen, or timing be changed.
• If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. This drug may cause birth defects if either the male or female is taking it at the time of conception or during pregnancy. Check with your doctor about what kinds of birth control can be used with this medicine.
• If you are breast-feeding. It is not known if this drug passes into breast milk. If it does, it could harm the baby.
• If you think you might want to have children in the future. Some drugs can cause sterility. Talk with your doctor about the possible risk with this drug and the options that may preserve your ability to have children.
• About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

Certain drugs that are used to treat bowel inflammation and ulcerative colitis, such as olsalazine (Dipentum), sulfasalazine (Azulfidine), mesalamine (Asacol, Canasa) may raise the blood levels of thioguanine and cause worse side effects. Your doctor may need to watch you more closely.

Any drugs or supplements that interfere with blood clotting can raise the risk of bleeding during treatment with thioguanine. These include:

• vitamin E
• non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen (Advil, Motrin), naproxen (Aleve, Naprosyn), and many others
• warfarin (Coumadin)
• ticlopidine (Ticlid)
• clopidogrel (Plavix)

Note that many cold, flu, fever, and headache remedies contain aspirin or ibuprofen. Ask your pharmacist if you aren't sure what's in the medicines you take.

Check with your doctor, nurse, or pharmacist about other medicines, vitamins, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Thioguanine is usually taken once a day on an empty stomach, 1 hour before or 2 hours after a meal. The dose depends on your weight and the type of cancer you are being treated for. If your stomach gets upset, take an anti-nausea pill an hour before you take the thioguanine.

Take this drug exactly as your doctor tells you to. If you are unsure of the dose or other instructions, call your doctor or nurse and ask that they explain them to you.

Store the medicine in a tightly closed container away from heat and moisture and away from children and pets.

Precautions

Do not get any immunizations (vaccines), either during or after treatment with this drug, without your doctor's OK. Thioguanine may affect your immune system. This could make vaccinations ineffective, or could even lead to serious infections if you get a live virus vaccine during or soon after treatment. Try to avoid contact with people who have recently received a live virus vaccine, such as the oral polio vaccine or smallpox vaccine. Check with your doctor about this.

Your doctor will likely test your blood throughout your treatment, looking for possible effects of the drug on blood counts (described below) or on other body organs. Based on the test results, you may be given medicines to help treat any effects. Your doctor may also need to reduce or delay your next dose of this drug, or even stop it altogether. Keep all your appointments for lab tests and doctor visits.

This drug can lower your white blood cell count, especially in the weeks after the drug is given. This can increase your chance of getting an infection. Be sure to let your doctor or nurse know right away if you have any signs of infection, such as fever (100.5° or higher), chills, pain when passing urine, a new cough, or bringing up sputum.

This drug may lower your platelet count in the weeks after it is given, which can increase your risk of bleeding. Speak with your doctor before taking any drugs or supplements that might affect your body's ability to stop bleeding, such as aspirin or aspirin-containing medicines, warfarin (Coumadin), or vitamin E. Tell your doctor right away if you have unusual bruising, or bleeding such as nosebleeds, bleeding gums when you brush your teeth, or black, tarry stools.

This drug may lower your red blood cell count. If this occurs, it is usually a few weeks after starting treatment. A low red blood cell count (known as anemia) can cause shortness of breath, or make you to feel weak or tired all the time. Your doctor may give you medicines to help prevent or treat this condition, or you may need to get blood transfusions.

You may have nausea and vomiting while you are taking this drug. Ask your doctor for a prescription for an anti-nausea medicine that you can take at home. It is important to have these medicines on hand and to take them as prescribed by your doctor.

This drug can kill large numbers of cancer cells within the first 24 hours of treatment, spilling the cells' contents into the blood. This can lead to electrolyte imbalances and tumor lysis syndrome, which can result in serious kidney damage and other problems. If your doctor thinks you may be at risk, he or she will give you medicines and/or fluids to help prevent it. Drink plenty of fluids while taking this drug.

This drug can cause severe liver damage in a few people. Call your doctor right away if you notice nausea, vomiting, fatigue, poor appetite, dark urine, yellowing skin or eyes, or tenderness under the right side of the rib cage.

Avoid pregnancy during treatment and for some months afterward. This drug may harm a growing fetus. Talk with your doctor about this.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.

Common

• nausea*
• vomiting*
• decreased platelet count with increased risk of bleeding*
• decreased white blood cell count with increased risk of infection*
• headache
• darkening of the skin
• weakness or aching
• tiredness (fatigue)

Less common

• high uric acid levels in the blood, with worsening of gout
• loss of appetite

Rare

• sores in mouth or on lips
• unsteady gait
• liver damage with poor appetite, yellow skin or eyes, or tenderness under the right side of the ribs*
• damage to the intestine
• kidney damage*
• death due to infection or other cause

*See the "Precautions" section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved before 1984. (FDA cannot verify dates of drugs approved before 1984.)

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.