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

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 ?

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