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Drug Class: Commonly Known As: Category:
Immune Suppressant Cancer-related, Children, Adult

Mercaptopurine - What is it for

Mercaptopurine is an anticancer medication used in the treatment of leukemia.

It works by interfering with the deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) production, hence impeding the growth of leukemic cells.

Mercaptopurine - Side Effects, Precautions, and Contraindications

What side effects can Mercaptopurine cause?

Possible side effects from Mercaptopurine and their management are listed in the following table. Always inform the doctor if your child experiences any side effects, so that the necessary monitoring may be conducted. Seek immediate medical attention if side effects are serious and urgent (refer to “Management”).

​Low white blood cell counts

White blood cells protect the body by fighting bacteria (germs) that cause infection.

When the number of white blood cells is low, your child will be more susceptible to infections and may become very ill from these infections.

To help prevent infection:

  • Wash hands regularly, especially before eating and after using the bathroom.
  • Avoid crowded places and avoid contact with people who are sick.
  • Do not eat raw or undercooked food.

​Seek medical help immediately if your child experiences any of the following:

  • Fever (temperature of 38˚C twice or ≥38.5˚C once)
  • Bleeding in stools (bloody or black, tarry stools) or urine
  • Any uncontrollable or persistent bleeding or bruising.

​Low platelet counts

Platelets are important for blood clotting. With low platelets, your child may bruise or bleed (for e.g. gums or nose) more easily than usual.

​Be safety conscious.

Brush teeth gently with a soft-bristled toothbrush.

Low red blood cell counts

Red blood cell transport oxygen to body cells. Your child may feel tired or lethargic if red blood cell is low.

Ensure child gets ample rest

Liver problems

Mild, transient changes to liver function may occur


Your doctor will monitor liver function using blood tests during therapy, and make adjustment to the therapy if necessary.

In the rare event that yellowing of skin and/ or eye(s), dark coloured urine, pale coloured stools, or pain in the upper stomach occurs, seek medical help immediately.

Skin reaction

Mild skin rash, hyperpigmentation of skin may occur.

Avoid excessive exposure to sunlight. Use sunscreen and wear protective clothing i.e. long-sleeved tops.

Seek medical help immediately in case of persistent rash or allergic reaction: itchy rash, blistered, peeling skin, swelling in face/ lips/ tongue/ throat, tightness in chest or throat, trouble breathing.

Nausea, vomiting, loss of appetite or diarrhea may rarely occur.

​​Seek medical help immediately if severe or persistent vomiting or diarrhea occurs.

​Hair loss may rarely occur.

Use gentle shampoo and soft hairbrush.​


Before taking Mercaptopurine , what precautions must I follow?

What food or medicine must I avoid when I take Mercaptopurine ?

Mercaptopurine - Dosage and How to Use

How should Mercaptopurine be used?

Mercaptopurine should be taken once daily in the evening, at the same time every day.

Mercaptopurine is available in tablet form.

To maximise absorption of Mercaptopurine, it should preferably be taken on empty stomach, i.e. either 1 hour before or 2 hours after food. However, if gastric discomfort is experienced whilst on Mercaptopurine, it may be taken with food.

Avoid milk or milk products 1 hour before and 2 hours after taking Mercaptopurine as milk products will affect the absorption of Mercaptopurine. Milk or milk products may be consumed at other times of the day.

If dose prescribed is less than one tablet (for e.g. half tablet or quarter tablet), use a tablet-cutter to cut the tablets in a still-air room. If your child is unable to swallow the tablet, soak the tablet in small volume of water and allow it to dissolve before administering the dose.

  • Take precautions to avoid cytotoxic exposure: wear gloves and mask when handling the tablets. Please refer to Patient’s Information Leaflet on “Safe Handling of Oral Cytotoxic Medications” for details.


Your doctor may change the dosage of Mercaptopurine depending on blood tests results. Always follow the doctor’s instructions strictly, and record the dose taken daily on the form given to you. Do not stop taking Mercaptopurine unless you are told to do so by your doctor. Do not take more or less than required unless instructed.

What should I do if I miss a dose?

If you forget a dose, take it as soon as you remember. If it is nearer to the time of the next dose, skip the missed dose. Do not take two doses at the same time.

Do not repeat dose if vomiting occurs after dose is administered, wait until the next scheduled dose. Contact the pharmacist or doctor if you repeatedly miss doses due to vomiting.

What should I do if I overdose?

Mercaptopurine - Handling

How should I handle Mercaptopurine safely?

​Please refer to Patient’s Information Leaflet on “Safe Handling of Oral Cytotoxic Medications” for details.

Mercaptopurine - Storage

How should I store Mercaptopurine ?

;#Keep away from children;#Keep in a cool, dry place, away from direct sunlight;#Store at room temperature;# Store the medication in the original container it came in

How should I dispose of Mercaptopurine safely?

​Please refer to Patient’s Information Leaflet on “Safe Handling of Oral Cytotoxic Medications” for details.

Mercaptopurine - Additional Information

Do not take this medication if your child is allergic to Mercaptopurine.

Do not give your child any other medications or herbal products without consulting your doctor or pharmacist. Some medication or food may reduce Mercaptopurine efficacy, or increase incidence of side effects. These include:

  • Blood thinning medications such as Warfarin
  • Allopurinol
  • Sulfasalazine, Mesalazine
  • Live vaccines, such as BCG, MMR and some forms of polio or influenza vaccines

Disclaimer: The list is not exhaustive. When in doubt, please consult the doctor or pharmacist.

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