Care During Chemotherapy and Beyond


(thye oh GWAH neen)

Trade Name: Tabloid ®
Other Names: 6-TG , 6-Thioguanine, 2-Amino-6-Mercaptopurine

Thioguanine is the generic name for the trade name drug Tabloid. In some cases health care professionals may use the trade name Tabloid®, or other names 6-TG, 6-Thioguanine, 2-Amino-6-Mercaptopurine when referring to the generic drug name thioguanine.

Drug Type: Thioguanine is an anti-cancer ("antineoplastic" or "cytotoxic") chemotherapy drug. Thioguanine is classified as an "antimetabolite." (For more detail, see "How thioguanine works" section below).

What thioguanine is used for:

  • Acute myelogenous leukemia (AML)
  • Acute lymphoblastic leukemia (ALL)

Note: If a drug has been approved for one use, physicians may elect to use this same drug for other problems if they believe it may be helpful.

How thioguanine is given:

  • As a tablet by mouth. Comes in one tablet size(40 mg)
  • Total daily dose may be given at one time, once a day.
  • The amount of thioguanine that you will receive depends on many factors, including your height and weight, your general health or other health problems, and the type of cancer or condition being treated. Your doctor will determine your exact dosage and schedule.

Side effects of thioguanine:

Important things to remember about the side effects of thioguanine:

  • Most people do not experience all of the side effects listed.
  • Thioguanine side effects are often predictable in terms of their onset and duration.
  • Thioguanine side effects will improve after therapy is complete
  • Thioguanine side effects may be quite manageable. There are many options to help minimize or prevent the side effects of thioguanine.

The following common side effects are reported (occurring in greater than 30%) for patients taking mercaptopurine:

  • Low blood counts . Your white and red blood cells and platelets may temporarily decrease. This can put you at increased risk for infection, anemia and/or bleeding. The lowest point of your blood counts occurs during the “nadir”. Nadir means low point, and this is the point in time between chemotherapy cycles in which you experience low blood counts. The following timeline describes when the nadir begins and when your blood counts should recover from your treatment:
  • Onset: 7-10 days
  • Nadir: 14 days
  • Recovery: 21-28 days

These are less common side effects (occurring in about 10-29%) for patients receiving thioguanine:

  • Mild swelling of the legs, hands, feet, or feeling more “bloated” (increase in water weight)
  • Signs of infection such as redness or swelling, pain on swallowing, coughing up mucous, or painful urination
  • Mouth sores (painful redness, swelling or ulcers)
  • Nausea (usually mild)
  • Poor appetite
  • Increases in blood tests measuring liver function. These return to normal once treatment is discontinued. (see liver problems)

These are rare but serious side effects for patients receiving mercaptopurine:

  • Tumor lysis syndrome may occur as a result of leukemia treatment. Tumor lysis syndrome occurs when large amounts of cancerous cells are rapidly killed by the therapy. These cells release uric acid, potassium and phosphorus into the blood stream. Tumor lysis syndrome can lead to kidney failure. Tumor lysis syndrome usually occurs within 24 - 48 hours of therapy. Care must be taken to prevent the development of tumor lysis syndrome. Your health care provider will prescribe plenty of fluids to keep you hydrated. You may be given a drug called allopurinol that blocks uric acid production. In some cases, your health care provider may prescribe other measures to lower your white blood count before therapy. Let your health care provider know immediately if you are unable to urinate. Your health care provider will monitor your progress carefully during therapy.
  • Thioguanine is potentially carcinogenic, and may increase your risk for developing secondary cancers. Long-term use of this drug is associated with a higher risk of developing a secondary cancer after treatment with thioguanine.
  • Your fertility, meaning your ability to conceive or father a child, may be affected by thioguanine. Please discuss this issue with your health care provider.

Not all side effects are listed above. Some that are rare (occurring in less than 10% of patients) are not listed here. However, you should always inform your health care provider if you experience any unusual symptoms.

When to contact your doctor or health care provider:

Contact your health care provider immediately, day or night, if you should experience any of the following symptoms:

  • Fever of 100.4° F (38° C) or higher, chills (possible signs of infection)
  • Painful upper abdomen along with rapid weight gain and/or swelling

The following symptoms require medical attention, but are not an emergency. Contact your health care provider within 24 hours of noticing any of the following:

  • Yellowing of the skin or eyes
  • Unusual bleeding or bruising
  • Black or tarry stools, or blood in your stools or urine
  • Extreme fatigue (unable to carry on self-care activities)
  • Nausea (interferes with ability to eat and unrelieved with prescribed medication)
  • Vomiting (vomiting more than 4-5 times in a 24 hour period)
  • Diarrhea (4-6 episodes in a 24-hour period)
  • Difficult or painful breathing, or having trouble catching your breath

Always inform your health care provider if you experience any unusual symptoms.


  • Before starting thioguanine treatment, make sure you tell your doctor about any other medications you are taking (including prescription, over-the-counter, vitamins, herbal remedies, etc.). Do not take aspirin, or products containing aspirin unless your doctor specifically permits this.
  • Before starting any over-the-counter, vitamin, or herbal remedies please consult your doctor or healthcare provider
  • Do not receive any kind of immunization or vaccination without your doctor's approval while taking thioguanine.
  • If you are taking a medication known as clozapine (Clozaril®) for treatment of schizophrenia, your blood work may need to be monitored more frequently or clozapine may be stopped altogether.
  • If you are taking a medication known as natalizumab (Tysabri®) you may be at a higher risk for infection.
  • Inform your health care professional if you are pregnant or may be pregnant prior to starting this treatment. Pregnancy category D (thioguanine may be hazardous to the fetus. Women who are pregnant or become pregnant must be advised of the potential hazard to the fetus).
  • For both men and women: Do not conceive a child (get pregnant) while taking thioguanine. Barrier methods of contraception, such as condoms, are recommended. Discuss with your doctor when you may safely become pregnant or conceive a child after therapy.
  • Do not breast feed while taking thioguanine.

Self-care tips:

  • Drink at least two to three quarts of fluid every 24 hours, unless you are instructed otherwise.
  • You may be at risk of infection so try to avoid crowds or people with colds and those not feeling well, and report fever or any other signs of infection immediately to your health care provider.
  • Wash your hands often.
  • Use an electric razor and a soft toothbrush to minimize bleeding.
  • Avoid contact sports or activities that could cause injury.
  • Thioguanine causes little nausea. But if you should experience nausea, take anti-nausea medications as prescribed by your doctor, and eat small frequent meals. Sucking on lozenges and chewing gum may also help.
  • In general, drinking alcoholic beverages should be kept to a minimum or avoided completely. You should discuss this with your doctor.
  • Get plenty of rest.
  • Maintain good nutrition.
  • If you experience symptoms or side effects, be sure to discuss them with your health care team. They can prescribe medications and/or offer other suggestions that are effective in managing such problems.

Monitoring and testing while taking thioguanine:

You will be checked regularly by your health care professional while you are taking thioguanine, to monitor side effects and check your response to therapy. Periodic blood work to monitor your complete blood count (CBC) as well as the function of other organs (such as your kidneys and liver) will also be ordered by your doctor.

How thioguanine works:

Cancerous tumors are characterized by cell division, which is no longer controlled as it is in normal tissue. "Normal" cells stop dividing when they come into contact with like cells, a mechanism known as contact inhibition. Cancerous cells lose this ability. Cancer cells no longer have the normal checks and balances in place that control and limit cell division. The process of cell division, whether normal or cancerous cells, is through the cell cycle. The cell cycle goes from the resting phase, through active growing phases, and then to mitosis (division).

The ability of chemotherapy to kill cancer cells depends on its ability to halt cell division. Usually, the drugs work by damaging the RNA or DNA that tells the cell how to copy itself in division. If the cells are unable to divide, they die. The faster the cells are dividing, the more likely it is that chemotherapy will kill the cells, causing the tumor to shrink. They also induce cell suicide (self-death or apoptosis).

Chemotherapy drugs that affect cells only when they are dividing are called cell-cycle specific. Chemotherapy drugs that affect cells when they are at rest are called cell-cycle non-specific. The scheduling of chemotherapy is set based on the type of cells, rate at which they divide, and the time at which a given drug is likely to be effective. This is why chemotherapy is typically given in cycles.

Chemotherapy is most effective at killing cells that are rapidly dividing. Unfortunately, chemotherapy does not know the difference between the cancerous cells and the normal cells. The "normal" cells will grow back and be healthy but in the meantime, side effects occur. The "normal" cells most commonly affected by chemotherapy are the blood cells, the cells in the mouth, stomach and bowel, and the hair follicles; resulting in low blood counts, mouth sores, nausea, diarrhea, and/or hair loss. Different drugs may affect different parts of the body.

Thioguanine is an antimetabolite. Antimetabolites are very similar to normal substances within the cell. When the cells incorporate these substances into the cellular metabolism, they are unable to divide. Antimetabolites are cell-cycle specific. They attack cells at very specific phases in the cycle. Antimetabolites are classified according to the substances with which they interfere.

Note: We strongly encourage you to talk with your health care professional about your specific medical condition and treatments. The information contained in this website is meant to be helpful and educational, but is not a substitute for medical advice.


Thioguanine.Lexicomp Online® [updated 2015 June 3; cited 2015 July 12]. Lexi-Drugs®. Hudson, Ohio: Lexi-Comp, Inc.; July 12, 2015. is designed to provide the latest information about chemotherapy to patients and their families, caregivers and friends. For information about the 4th Angel Mentoring Program visit