Mercaptopurine
Indications
Mercaptopurine is used mainly to treat acute lymphoblastic leukaemia (ALL), a blood cancer, especially in the long maintenance phase of treatment. Specialists also use it to control inflammatory bowel disease (Crohn's disease and ulcerative colitis) when other treatments are not enough.
How It Works
Mercaptopurine is a purine antimetabolite. It looks like one of the building blocks of DNA, so fast-dividing cells take it up by mistake. This stops them making DNA properly, which slows the growth of cancer cells and calms an overactive immune system.
Dosage and Administration
Take exactly as prescribed by your specialist. The dose depends on body size, blood counts, genetic tests (TPMT or NUDT15) and the condition being treated, and it is adjusted often. Take it at the same time each day, usually in the evening, either always with or always without food; avoid taking it with milk. Swallow tablets whole and wash hands after handling them.
Interactions
- Allopurinol and Febuxostat greatly raise mercaptopurine levels; the dose must be cut sharply or the combination avoided.
- Methotrexate, other anticancer drugs and Co-trimoxazole increase the risk of low blood counts.
- It may reduce the effect of Warfarin.
- Live vaccines must be avoided during treatment.
Contraindications
- Allergy to mercaptopurine.
- Live vaccines such as yellow fever during treatment.
Side Effects
Common: low white cells, red cells and platelets, nausea, loss of appetite, mouth ulcers and raised liver enzymes. Serious: severe infections, liver damage, pancreatitis and, rarely, certain cancers with long-term use. Sun sensitivity can increase skin cancer risk.
Get urgent medical help for fever, chills or sore throat, unusual bruising or bleeding, yellow skin or eyes, dark urine, or severe tummy pain.
Pregnancy and Lactation
Mercaptopurine may harm an unborn baby. Use reliable contraception during treatment, and discuss family planning with your specialist. Small amounts pass into breast milk; breastfeeding is generally not advised unless the specialist agrees.
Precautions and Warnings
- Regular blood counts and liver tests are needed.
- Avoid people with chickenpox or shingles, and report any infection early.
- Use sunscreen and protective clothing.
- Do not stop or change the dose on your own.
Overdose
Overdose can cause nausea, vomiting, diarrhoea and dangerously low blood counts. Go to hospital immediately if too much has been taken.
Therapeutic Class
Antineoplastic antimetabolite (purine analogue); immunosuppressant.
Storage
Store below 30°C in a dry place, away from light and out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.
All brands of Mercaptopurine