What does it do?

Mercaptopurine is an immunosuppressant medicine used to treat inflammatory bowel disease, such as Crohn’s disease. It calms down your overactive immune system that causes inflammation in your bowel. It is also used for other conditions.

Before you start

• Tell your doctor if you have kidney or liver problems, or if you have taken immunosuppressant medicines in the past.
• Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.
• You will need a blood test to check if mercaptopurine is suitable for you.
• Mercaptopurine weakens your immune system, making it harder for your body to fight infections. You may need tests before you start to make sure you don't have any infections like tuberculosis (TB), HIV, or hepatitis B and C.
• Ask your doctor what vaccines you might need before you start and while you are taking mercaptopurine. You should not have a live vaccine while taking mercaptopurine.

How should you take it?

Take mercaptopurine regularly as directed with a glass of water. Swallow the tablets whole – do not break, crush or chew.

What if you forget a dose?

If it is nearly time for your next dose, skip the missed dose and take your next dose at the usual time. Otherwise, take the missed dose as soon as you remember. Do not take two doses at the same time.

Can you take other medicines?

Tell your pharmacist or doctor about all medicines or treatments that you may be taking, including vitamins, herbal products (e.g. echinacea) or recreational drugs.

What side effects might you notice?

Side Effects	Recommended action
Reduced number of blood cells that fight infections or help your blood to clot - symptoms include: fever, chills, sore throat or generally feeling unwell, or easy or unusual bruising or bleeding Severe stomach pain Symptoms of liver problems including: yellow skin or eyes, itching, dark urine, pale bowel motions, abdominal pain	Tell your doctor immediately
Skin rash	Tell your doctor
Vomiting, diarrhoea	Tell your doctor if troublesome
Nausea	Take with food

If you notice any other effects, discuss them with your doctor or pharmacist.

Other information:

• You will need regular blood tests while you are taking mercaptopurine to check if it is causing problems with your liver or blood, and to make sure you are on the right dose.
• Protect yourself from too much sunlight while taking immunosuppressant medicines (they may increase your risk of skin cancer). Always cover up and apply a thick layer of broad spectrum sunscreen (at least SPF30) when outside. Do not use sunbeds.
• Women using mercaptopurine for a long time may need cervical screening more often. Discuss with your doctor.
• It is important to tell anyone who gives you medical or dental treatment that you are taking mercaptopurine.