Medication Information Leaflet

What is this medication for?

Thioguanine, or tioguanine (6-TG) is commonly used for the treatment of leukaemia (cancer of the blood). The medication works by slowing the growth of cancer cells.

How should I take/use this medication?

You may take this medication 1 hour before or 2 hours after food.

Do not stop taking your medication without checking with your healthcare professional.

If possible, handle the medication yourself. If a family member or caregiver needs to give the medication, do wash their hands before and after handling the medication.

What should I do if I forget to take/use this medication?

If you forget to take a dose, take it as soon as you remember if it is within 12 hours of the missed dose. Then take your next dose at the usual time.

If it is more than 12 hours since your missed dose, skip the missed dose and take the next dose at usual dosing time. Do not take two doses to make up for the missed dose.

What precautions should I take?

Inform your healthcare professional if:

  • You are allergic to this medication or any of the other ingredients of this medication
  • You are pregnant, planning to become pregnant, or breastfeeding
  • You are taking any other medications, including supplements, traditional medications and herbal remedies

What are some common side-effects of this medication?

  • Temporary decrease in blood cell counts
    • This may put you at higher risk of infections, bleeding or bruising and feeling tired
    • Reduce your risk of getting an infection by:
      • Maintaining good hand hygiene. Wash your hands often during the day especially before you eat or after using the toilet
      • Avoid crowded spaces and wear a mask to protect yourself
      • Eating freshly cooked food. Avoid raw meats, vegetables, eggs, half-cooked or uncooked food
    • Brush teeth gently with a soft bristle toothbrush to prevent gum bleeding
    • Be careful when handling sharp objects such as scissors or knives
  • Increase sensitivity to sunlight
    • Avoid excessive sunlight exposure
    • Apply broad spectrum sunscreen with sunscreen protection factor (SPF) of at least 30
    • Wear protective clothing if you are exposed to direct sunlight
  • Loss of appetite
    • Take small and frequent meals
  • Nausea and/or vomiting
    • Take small and frequent meals, rather than 3 large meals
    • Consume food that are cold or at room temperature to avoid becoming nauseated from the smell
  • Mouth sores and/or ulcers
    • Observe good oral hygiene. Use a soft-bristle toothbrush.
    • Gargle mouth with salt water after each meal. Avoid mouthwashes that contain alcohol.
    • Avoid foods and drinks that are too hot and spicy
  • Tumor lysis syndrome
    • This condition is caused by a fast breakdown of cancer cells
    • Reduce your risk by drinking 6 to 8 glasses of water each day, starting 2 days before your first dose.
    • Inform your doctor immediately if you experience any unusually fast heartbeat, muscle weakness or cramps or pain, dark and cloudy urine, unusual tiredness or seizures

What are some rare but serious side-effects that I need to seek medical advice immediately?

The symptoms of a drug allergy include one or more of the following:

  • Swollen face/eyes/lips/tongue
  • Difficulty in breathing
  • Itchy skin rashes over your whole body

Other serious side effects include:

  • Infections
    • Signs of an infection include:
      • Fever (temperature over 38°C)
      • Chills
      • Severe sore throat
      • Cough with thick or green phlegm
      • Cloudy or foul smelling urine
      • Painful, tender, or swollen red skin wounds or sores
  • Unusual bleeding
    • Signs of unusual bleeding include:
      • Bruising without a cause or bruise that worsens
      • Dark (black or red), sticky stools
      • Coughing out blood
      • Vomit that looks like coffee grounds
      • Passing blood in the urine
      • Bleeding that you cannot stop
  • Liver problems:
    • Signs of liver problems include:
      • Dark or tea-coloured urine
      • Pale or light-coloured stools
      • Yellowing of skin or eyes
      • Severe loss of appetite
      • Abdominal pain
      • Nausea or vomiting that does not go away
  • Excessive weight gain or swelling of belly

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

What food or medication should I avoid when I take this medication?

Avoid alcohol when taking Thioguanine as it may increase the risk of liver problems.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children.

How should I throw away this medication safely?

Pack the medication into a bag and bring it back to the pharmacy where you received the medication from.


Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on Aug 2023

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