Dr Dafydd Bowen Gastroenterology

Inflammatory Bowel Disease (IBD)

IBD is generally categorised into two types, Ulcerative Colitis and Crohn's Disease. Ulcerative colitis can cause diarrhoea which is often stained with blood. Crohn's can be similar to ulcerative colitis but can also cause other symptoms such as severe abdominal pain, vomiting, weight loss and discharge around the anus.

Once diagnosed the aim of treatment is to control the disease. Currently there is no cure and the cause remains unclear. Current research would suggest that there is both a genetic and an environmental trigger. A popular theory is that the immune system fails to ignore the normal bacteria in the bowel, resulting in inflammation at the lining of the bowel.

Treatment depends on the severity of the inflammation. In mild cases, anti-inflammatories are used. These are designed to release the anti-inflammatory drug at the site of inflammation. The common drug used is Mesalazine and it comes in many versions (Asacol, Mezavant, Pentasa, Octasa). All are broadly similar in effect. These drugs are not generally absorbed into the bloodstream and as such have very few side effects. The limitation with this drug is that it is only for mild to moderate disease.

Moderate to severe disease requires suppression of the immune system. This can be achieved with steroids, Azathioprine, Methotrexate and biological drugs. All these drugs can be very effective for IBD but the choice of agent depends on each patient. There are many things to consider here such as the type of disease, patient preference and previous exposure to other drugs. These options are best discussed with your specialist.

The course of the disease is variable. In some patients the disease may be so aggressive that it requires surgery. Most patients however can be controlled with medication. Flare-ups of the disease may occur between long periods of remission. The treatments above have a role in keeping the disease in remission.

An excellent source of information for IBD can be found on the Crohns & Colitis UK website.

Azathioprine and Mercaptopurine

These two drugs are similar. Azathioprine is sent to the liver and converted to Mercaptopurine. These drugs suppress the immune system and are used when steroids are required frequently to control symptoms. Steroids have unpleasant long term side effects, these two drugs are used in place of steroids if they are required frequently.

These drugs take 2-3 months to become fully effective (unlike steroids). Your suitability for the drug is often assessed with a blood test (TPMT), usually checked shortly after diagnosis. This checks that your body can remove the drug appropriately. Usual doses are 1-2.5mg/Kg of Azathioprine and 0.5-1mg/Kg of Mercaptopurine. These drugs are used for lengthy periods, often years. The length of treatment depends on individual cases. 70% will achieve a good long term remission on these drugs.

Side effects such as nausea, headache and abdominal pain can occur and are usually not serious but may be unpleasant. Switching to Mercaptopurine may avoid these side effects. Initially blood tests are required every 2-4 weeks and when stable every 2 months to monitor the white blood cells, liver and kidneys. This monitoring can be done with your GP. Other side effects include increased infections and photosensitivity.

Azathioprine can interact with other drugs. Ensure your prescriber is aware of other medicines you are on and also if another doctor prescribes you anything then mention that you are on Azathioprine/Mercaptopurine. Important drugs to be wary of are Allopurinol, Warfarin and some antibiotics. Live vaccines should also be avoided.

More information relating to medicines can be found on the Crohn's and Colitis UK website:

Azathioprine and Mercaptopurine

Drugs Used in IBD