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Overview: Thioguanine is used to treat a certain type of leukemia. Common side effects include blood disorders and high levels of uric acid. Call your health care provider right away if you have easy bruising, bleeding, or an infection. These could be signs of a serious side effect. Thioguanine is a tablet that is taken by mouth.

Uses

What is thioguanine used for?

Thioguanine is commonly used to treat certain people with a type of blood cancer called acute myeloid leukemia (AML).

Thioguanine may also be used for other conditions as determined by your health care provider.

How does thioguanine work (mechanism of action)?

Thioguanine is a type of chemotherapy. It works by preventing RNA and DNA in cancer cells from working correctly. This helps stop the cancer cells from growing and multiplying, which can help slow or stop the spread of cancer.

How is thioguanine supplied (dosage forms)?

Brands and other names

  • Tabloid

Dosage forms and strengths

  • 40 mg oral tablets

How should I store thioguanine?

Thioguanine should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. 

Side Effects

What are the most common side effects of thioguanine?

The most common side effects of thioguanine are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Blood disorders (see below)
  • High levels of uric acid

There may be other side effects of thioguanine that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of thioguanine?

While less common, the most serious side effects of thioguanine are described below, along with what to do if they happen.

Severe Allergic Reactions. Thioguanine may cause allergic reactions, which can be serious. Stop taking thioguanine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Blood Disorders. Thioguanine can cause blood disorders, such as low red blood cell levels (anemia), low platelet levels (thrombocytopenia), and low white blood cell levels (leukopenia). It is important to go to all appointments for blood work to make sure thioguanine is safe for you. Get help right away if you have any of the following symptoms of blood disorders.

  • Fever
  • Shortness of breath
  • Pale or yellowish skin
  • Easy bruising or bleeding
  • Frequent infection
  • Unusual weakness or tiredness
  • Dizziness, lightheadedness, or feeling like you are about to pass out
  • Headache
  • Fast or abnormal heartbeat

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking thioguanine. Stop taking thioguanine and call your health care provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Warnings & Precautions

Who should not use thioguanine?

Allergies to Ingredients. People who are allergic to any of the following should not take thioguanine.

  • Thioguanine
  • Tabloid
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific thioguanine products they stock.

Prior Use of Certain Medicines. Tell your health care provider if you have taken thioguanine or mercaptopurine in the past and they did not help your condition. Thioguanine should not be taken if these medicines did not work for you in the past.

What should I know about thioguanine before using it?

Do not take thioguanine unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share thioguanine with other people, even if they have the same condition as you. It may harm them.

Keep thioguanine out of the reach of children.

It is important to attend all appointments for blood work with your health care provider. They will use these tests to monitor your body’s response to thioguanine and make sure it is safe for you to continue taking the medicine. 

Thioguanine may make it hard for you to get pregnant or get your partner pregnant. If you have concerns, talk to your health care provider.

What should I tell my health care provider before using thioguanine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if thioguanine is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Liver problems
  • A deficiency of the enzyme thiopurine methyltransferase (TPMT) or nudix hydrolase 15 (NUDT15)
  • Prior treatment with thioguanine or mercaptopurine

Other Medicines and Supplements. Thioguanine may interact with other medicines and supplements. Before taking thioguanine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Thioguanine may cause harm to a fetus. Your health care provider may make sure you are not pregnant before starting thioguanine. If you can become pregnant, you should use effective birth control while taking thioguanine. Tell your health care provider if you are pregnant, think you might be pregnant, or plan to become pregnant.

Breastfeeding. It is not known if thioguanine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will advise you if you should stop breastfeeding or stop thioguanine.

Vaccines. Talk with your health care provider about any vaccines that you may need. You may not be able to receive certain vaccines right before or while taking thioguanine. Tell your health care provider about any vaccines you have recently received or have scheduled.

Interactions

Does thioguanine interact with foods or drinks?

There are no known interactions between thioguanine and foods or drinks.

It is unknown if drinking alcohol will affect thioguanine, but heavy drinking can slow your immune response and make it harder for your body to fight cancer.

Does thioguanine interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking thioguanine.

  • Mercaptopurine, which is a medicine that may be used to treat leukemia
  • An aminosalicylate derivative, such as mesalamine, olsalazine (Dipentum), or sulfasalazine (Azulfidine), which is a medicine used to reduce inflammation (swelling)

This may not be a complete list of medicines that can interact with thioguanine. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much thioguanine?

If you or someone else has used too much thioguanine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of thioguanine?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.