THIOGUANINE (Systemic)

Some commonly used brand names are:

In the U.S.—

• Tabloid

In Canada—

• Lanvis

Generic name product may be available in the U.S.

Category

• Antineoplastic

Description

Thioguanine (thye-oh-GWON-een) belongs to the group of medicines known as antimetabolites. It is used to treat some kinds of cancer.

Thioguanine interferes with the growth of cancer cells, which are eventually destroyed. Since the growth of normal body cells may also be affected by thioguanine, other effects will also occur. Some of these may be serious and must be reported to your doctor. Other effects may not be serious but may cause concern. Some effects may not occur for months or years after the medicine is used.

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

Thioguanine is available only with your doctor's prescription, in the following 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 will do. This is a decision you and your doctor will make. For thioguanine, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to thioguanine.

Pregnancy—Tell your doctor if you are pregnant or if you intend to have children. There is a chance that this medicine may cause birth defects if either the male or female is taking it at the time of conception or if it is taken during pregnancy. In addition, many cancer medicines may cause sterility which could be permanent. Although this has not been reported with this medicine, the possibility should be kept in mind.

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

Breast-feeding—Tell your doctor if you are breast-feeding or if you intend to breast-feed during treatment with this medicine. Because thioguanine may cause serious side effects, breast-feeding is generally not recommended while you are receiving it.

Children—Children are especially sensitive to the effects of thioguanine. This may increase the chance of liver toxicity during treatment.

Older adults—Many medicines have not been tested in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information about the use of thioguanine in the elderly.

Other medicines—Although certain medicines should not be used together at all, in other cases two differen t medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking thioguanine, it is especially important that your health care professional know if you are taking any of the following:

• Antithyroid agents (medicine for overactive thyroid) or
• Azathioprine (e.g., Imuran) or
• Chloramphenicol (e.g., Chloromycetin) or
• Colchicine or
• Flucytosine (e.g., Ancobon) or
• Interferon (e.g., Intron A, Roferon-A) or
• Plicamycin (e.g., Mithracin) or
• Zidovudine (e.g., Retrovir) or
• If you have ever been treated with x-rays or cancer medicines—Thioguanine may increase the effects of these medicines or radiation therapy on the blood

• Mesalamine (e.g., Pentasa) or
• Olsalazine (e.g., Dipentum) or
• Sulfasalazine (e.g., Azulfidine)—May increase the effects of thioguanine on the blood

• Probenecid (e.g., Benemid) or
• Sulfinpyrazone (e.g., Anturane)—Thioguanine may increase the concentration of uric acid in the blood, which these medicines are used to lower

Other medical problems—The presence of other medical problems may affect the use of thioguanine. Make sure you tell your doctor if you have any other medical problems, especially:

• Chickenpox (including recent exposure) or
• Herpes zoster (shingles)—Risk of severe disease affecting other parts of the body

• Gout (history of) or
• Kidney stones (history of)—Thioguanine may increase levels of uric acid in the body, which can cause gout or kidney stones

• Infection—Thioguanine can reduce immunity to infection

• Kidney disease or
• Liver disease—Effects may be increased because of slower removal of thioguanine from the body

• Thiopurine methyltransferase deficiency (TPMT)—You may be more sensitive to the side effects of thioguanine, and your doctor may reduce your dose

• Tumors—Thioguanine should not be used if your tumor did not get smaller when previously treated with thioguanine