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Mercaptopurine - Oral


Patient Medicine Information
Why do I need this medicine?
Mercaptopurine is used together with other medicines to treat a certain type of blood cancer that starts in the white blood cells in the bone marrow, called acute lymphoblastic leukaemia.

This medicine may be used to treat other conditions as decided by your doctor.
How do I take this medicine?
Take Mercaptopurine exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.

Take this medicine consistently, either with or without food. Try to take it at the same time each day.

Mercaptopurine is available as a tablet or oral suspension.

If you are taking the oral suspension, shake the bottle well before you take the medicine to ensure that the liquid is evenly mixed. Use the measuring spoon or cup provided to measure your dose.

The dose of this medicine will be decided by your doctor. Your doctor will advise you on the course of treatment depending on the severity of your condition and your response to the medication.
What should I do if I have forgotten to take this medicine?
If you miss a dose, skip the missed dose and return to your normal dosing schedule.

DO NOT double a dose under any circumstances.

If you often forget to take your medicine, let your doctor and pharmacist know.
What should I take note of while taking this medicine?
Inform your doctor if you have the following conditions:
  • inflammatory bowel disease (group of diseases that cause long-term inflammation of the digestive tract)
  • kidney disease
  • liver disease
It is important that you do not get pregnant while being treated with this medicine. Both men and women must use proven birth control methods during Mercaptopurine therapy and for 3 months after stopping the treatment. You may wish to discuss reliable methods of birth control with your doctor.

Breastfeeding is not recommended while you are being treated with this medicine and for 1 week after the last dose.

Be sure to check with your doctor or pharmacist before giving this medicine to a child. Children may be more sensitive to the side effects.

Individuals who have reduced TPMT or NUDT15 gene activity, known as TPMT or NUDT15 poor metabolisers, may experience enhanced side effects of Mercaptopurine (e.g. myelosuppression, a condition in which the blood cells are low). Although not routinely done, your doctor may advise you to undergo genetic testing to check if this medicine is best suited for you. If you know you have this gene type, inform your doctor.

Inform your doctor if you have been recently vaccinated. Do not receive any vaccinations without first asking your doctor.

Why is it important to keep my appointments with the doctor?

Keep your appointments with your doctor. Your doctor needs to monitor your condition and check your response to the medication regularly.
  • Pregnancy tests must be done before treatment to know if this medicine is suited for you to take.
  • Routine tests (e.g. liver and kidney function, complete blood count) may be done while you are being treated with this medicine. Your doctor will advise you about how often you need to have these tests.
  • Regular monitoring of signs and symptoms of bleeding and infection may also be needed.
What side effects could I experience?
Mercaptopurine may cause any of the following side effects: nausea, vomiting, diarrhoea, decreased appetite, weakness, and rash.

This medicine may also make your skin more sensitive to sunlight. Apply sunscreen when going outdoors and avoid prolonged exposure to sunlight and UV lamps.

Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:
  • yellowing of the skin or eyes, abdominal pain, dark coloured urine, tiredness, swelling in the legs and ankles
  • skin lump or growth, changes in the colour or size of your mole
This medicine may cause the level of your red blood cells, white blood cells and platelets to drop.

Red blood cells carry oxygen around your body. A fall in the level of red blood cells may make you feel tired and worn out.

White blood cells help your body to fight infections. A fall in the level of your white blood cells may put you at higher risk for infections, such as coughs, colds and flu, which may lead to more serious infections. Avoid crowded places and people who are sick. Inform your doctor if you have a fever, cough, or flu that does not go away.

Platelets help your blood to clot when there is a cut in the skin. A fall in the level of your platelets may put you at risk of bleeding more than usual. Do not take part in activities where you may fall or get injured, such as contact sports. Inform your doctor if you get any unusual bruising (large bruises or several bruises, especially if the bruises appeared on their own) or bleeding that takes a long time to stop (for example, too much bleeding when you floss or brush your teeth).

Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Can I take this with other medicines?
Inform your doctor and pharmacist if you are taking any of these medicines:
  • medicines for gout (high uric acid level in the blood) e.g. allopurinol, febuxostat
  • medicines used to treat inflammatory bowel disease e.g. mesalazine, olsalazine, sulfasalazine
  • certain antibiotics e.g. trimethoprim, sulfamethoxazole
  • warfarin (blood-thinning medicine)
  • ribavirin (medicine for hepatitis C infection)
This list does not include all medicines that may interact with Mercaptopurine.

Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements, and medicines that you buy without a prescription.
What special dietary instructions should I follow?
Avoid alcohol.

Do not take Mercaptopurine with dairy products such as milk, cheese, yoghurt, or ice cream. Dairy products may reduce the effectiveness of this medicine when taken at the same time. Take this medicine at least 1 hour before or 2 hours after you have taken any dairy products.
How should I store this medicine?
Store in a cool, dry place away from the reach of children.

The oral suspension should be used within 8 weeks after opening.

Medicines must not be used past the expiry date.

As Mercaptopurine is a cancer medicine, always return any unused or expired medicine to the clinic, hospital, or pharmacy for disposal. Do not throw it away in the household waste.
This information is independently developed by MIMS based on Mercaptopurine - Oral and is provided for your reference only. It is not a replacement for and should only be used in conjunction with full consultation with a licensed healthcare professional, the information provided by your pharmacist and/or the manufacturer of the medication. It may not contain all the available information you require and cannot substitute professional medical care, nor does it take into account all individual circumstances. Although great effort has been made to ensure content accuracy, we shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2025 MIMS. All rights reserved. Powered by MIMS.com
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