Commonly Used GI Drugs

Patient Information

Azathioprine (Imuran)& 6 Mercaptopurine (Puri-Nethol)

Why am I being prescribed Azathioprine or 6 Mercaptopurine?

These drugs are frequently used in Ulcerative colitis & Crohn’s disease to reduce inflammation in the bowel and prevent relapse. Azathioprine comes in two strengths, 25mg and 50mg tablets, whilst 6 mercaptopurine comes in 50mg tablets. Doctors often prescribe this medication for patients whose disease flares either as the dose of steroids is reduced or within weeks of stopping steroids, or for patients who require more than two courses of steroids in a year.

How do the tablets work?

Azathioprine and 6 mercaptopurine (6MP), work by reducing the amount of inflammation in your bowel. They are known as an ‘immunosuppressant’ drugs, that is they suppress your immune system, but not so much that your body cannot fight against infections.  (Your immune system is a sophisticated system, which recognises and fights foreign organisms such as viruses and bacteria). Larger doses of some immunosuppressant were originally used to suppress the immune response in organ transplant patients to prevent rejection and also in treating some types of cancer or leukaemia. In your case, this is  not the reason that azathioprine and 6 mercaptopurine are being used.

You should not expect to see immediate improvement as such drugs act slowly and may take as long as three months to be fully effective.

What dose should I take?

Your doctor will prescribe the correct dose, which is calculated by your body weight. For Azathioprine, this is usually worked out as 2 - 2.5mg per kilogram of your body weight and for 6 Mercaptopurine, at a dose of 1mg per kilogram of your body weight The tablet should usually be taken as a single dose after meals and should be swallowed whole. Like many medications, azathioprine and 6 mercaptopurine can react with other drugs (particularly allopurinol, trimethoprine and rifampicin). It is therefore important that you inform your doctor, nurse, or pharmacist if you start taking other drugs, even those that you may buy over the counter. It is important that you remember to take your medication. However, if you were to forget a dose, take the tablets as soon as you remember unless it is nearly time for the next dose, when it is best to miss out the one you forgot.

What possible complications can result from taking azathioprine and 6 mercaptopurine?

It is important to remember that all drugs may have side effects, but many patients never experience any. Two thirds of patients can take azathioprine without any side effects at all. However, some patients experience a feeling of sickness when the treatment is first started. This often wears off after a few days, or can be reduced by splitting the dose (take one tablet twice a day, rather than two at once). If the sickness gets worse or if it is associated with headache or muscle aches, then stop the medication and try again with one tablet a day when symptoms have settled. If it reoccurs contact your GP or us. Many people who cannot tolerate azathioprine can tolerate 6 mercaptopurine. The most important side effect however, is a drop in the white cell count. This is rare but potentially serious, so the blood count is monitored regularly. Other rare side effects that can occur with azathioprine include thinning of the hair (although this can be due to inflammation in the bowel) rashes, or inflammation in the pancreas (this causes severe abdominal pain and vomiting). If you experience a sore throat, fever, chest infection or flu-like symptoms, YOU MUST CONTACT YOUR SPECIALIST OR YOUR GP IMMEDIATELY.

Are there any drugs that I cannot take with Azathioprine?

Allopurinol (Zyloric) increases the chance of developing side-effects to Azathioprine so should always be stopped prior to the commencement of treatment.

Other useful sources of information is a useful website:

What blood tests will I need?

Compliance is essential to the safety and effectiveness of your treatment. You should arrange regular blood tests with your GP. When first starting the tablet you will require a weekly full blood count & liver function test for the first four weeks. If your results are within normal ranges, the blood tests can then be reduced to once every 3 months for as long as you are taking the medication. It is best to get a small notebook to record the results. The white blood cell count (WBC) is the most important, this should be above 3.5.

How long will I need to take my medication?

Most patients need to take it for about five years as a rule but some patients may not need it for so long whilst others may need to continue their medication indefinitely. Do not stop taking your medication unless discussed with your doctor. Remember that you will need to arrange repeat prescriptions and should arrange your next supply with pharmacy two weeks prior to running out.

Do azathioprine and 6 mercaptopurine affect fertility or pregnancy?

If you are planning a family whilst taking this medication you must tell your doctor or nurse. Whilst usually safe, it is a complex issue that must be discussed with a specialist.

Can I drink alcohol with azathioprine?

Yes, it is perfectly safe.




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