mercaptopurine monohydrate at a glance
Medicine class
Cytotoxic chemotherapy; purine antimetabolite.
Licensed use
Acute lymphoblastic leukaemia in adults, adolescents and children.
Food and milk
Take consistently with or without food, and separate from milk and dairy products.
Monitoring
Regular blood counts and liver-function tests are essential.
What is mercaptopurine monohydrate used for?
The selected product is licensed for ALL. Other specialist uses are outside its marketing authorisation.
Licensed: acute lymphoblastic leukaemia in adults, adolescents and children.
Non-licensed context: inflammatory bowel disease, including Crohn’s disease and ulcerative colitis, under specialist supervision.
How does mercaptopurine monohydrate work?
Mercaptopurine is converted inside cells into active thioguanine nucleotides. These disrupt purine production and become incorporated into nucleic acids, limiting growth and division of rapidly proliferating cells.
mercaptopurine monohydrate preparations and strengths
Oral suspension
Route: Oral
Strengths: 20 mg/mL
How to take mercaptopurine monohydrate
Use the oral suspension exactly as instructed by the specialist team and measure it only with the supplied oral syringe.
Shake the bottle vigorously for at least 30 seconds before measuring.
Take with food or on an empty stomach, using the same approach consistently.
Take at least 1 hour before or 2 hours after milk or dairy products.
Drink water afterwards so no suspension remains in the mouth.
Wash hands before and after handling; carers should use disposable gloves and promptly wash spills from skin or mucous membranes.
mercaptopurine monohydrate side effects
Common or expected effects
- Reduced white blood cells or platelets, detected through blood tests
- Anaemia
- Loss of appetite
- Nausea, vomiting or diarrhoea
- Liver injury or reduced bile flow
Get urgent medical advice
- Bone-marrow suppression causing infection, fever, bruising or bleeding
- Severe infection, including neutropenic sepsis
- Liver injury causing jaundice
- Pancreatitis, which may cause abdominal pain and sickness
- Severe allergic reaction or facial swelling
- Rare malignancies associated with immunosuppression
mercaptopurine monohydrate in pregnancy
Pregnancy requires specialist assessment of the benefits of disease control against possible fetal risks. Current UK pregnancy information finds no good evidence that mercaptopurine itself harms the baby, but pregnancy-related cholestasis may occur and maternal or newborn monitoring may be needed. Do not change treatment without the specialist team.
mercaptopurine monohydrate while breastfeeding
The selected product information advises against breastfeeding during treatment. This is particularly relevant when mercaptopurine is used as antineoplastic chemotherapy; feeding options require specialist oncology and maternity review.
mercaptopurine monohydrate interactions
Check all prescribed, non-prescribed and complementary products with the specialist team. Important interactions include:
Allopurinol and other xanthine oxidase inhibitors
They reduce mercaptopurine breakdown and can markedly increase toxicity; specialist adjustment or avoidance is required.
Mesalazine, olsalazine and sulfasalazine
These may inhibit TPMT and increase the risk of bone-marrow toxicity.
Ribavirin
Concurrent use is not advised because severe bone-marrow suppression has been reported.
Common questions about mercaptopurine monohydrate
Answers are fully visible for fast scanning and source review.
Why are regular blood tests needed?
Mercaptopurine can suppress bone-marrow production of white cells, platelets and red cells. Tests can identify toxicity before serious infection, bleeding or anaemia develops.
Can it be taken with food?
Yes. It may be taken with or without food, but the chosen method should remain consistent.
Why separate it from milk and dairy products?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.