Bright Sight

Oliver Backhouse, Consultant Eye Surgeon www.cataract.org.uk

Treatment with Azathioprine

AZATHIOPRINE is a drug used to suppress the immune system. The immune system is responsible for fighting infections, but there may be circumstances where it is necessary to suppress its action. For instance, Azathioprine is given to patients with a kidney transplant to try and stop their body’s immune system from rejecting the kidney. Azathioprine is also used to treat auto-immune conditions. These conditions can result, for a variety of reasons, because the body’s immune system fails to recognise a part of itself, and reacts against it. This causes inflammation and scarring of the part affected. Some inflammations inside the eye (uveitis) are auto-immune diseases.

Azathioprine is taken by mouth in the form of tablets. The dose is around 50mg three times a day. It works by preventing some cells from dividing and reproducing so quickly and therefore reduces the ability of these cells to cause inflammation.

Most patients who use Azathioprine to treat uveitis are already using steroids (prednisolone). Information on this drug is also available. Azathioprine is usually given to reduce the dose of prednisolone in order to reduce side-effects. If Azathioprine is to be prescribed for your eye inflammation, you will need to know about potential side-effects of the drug, and the regular tests that will be performed in order to minimise problems.

1. The bone marrow and blood cells.

Azathioprine acts by preventing some white blood cells from causing inflammation. In a few patients there is a more generalised reduction in the number of white blood cells, which is undesirable. Rarely the red blood and clotting cells are also affected and this is also undesirable. There will be blood tests every few weeks and then every 3 months when stable.

Severe problems are rare and most patients have no problems with their bone marrow and blood counts. Bruising of the skin, bleeding from the gums, severe sore throat or infection should be reported to your doctor for an immediate examination and blood test.

2. Stomach irritation.

A few patients feel slightly sick when starting to take Azathioprine. This is not usually a major problem, and is minimised by taking the tablets after a meal. Rarely more severe irritation occurs. If this does occur it should be reported to your doctor immediately.

3. Infection.

Azathioprine alone, taken in small to moderate doses (as for the treatment of uveitis) is unlikely to lead to an increased infection risk. However it is usually used with prednisolone initially. When these 2 drugs are used together there is a greater infection risk than either drug used alone. Information on this topic is covered in the Prednisolone information leaflet.

4. Others.

If you are a woman, it is important you do not become pregnant when using Azathioprine as there is a small risk of damage to a baby. If necessary you should take contraceptive precaution. In a few people, hair loss can occur but is not common and unlikely to be severe. Occasionally the kidneys or liver are also affected and so regular bloods tests will be needed to make sure this is not happening. There is a theoretical risk of increased malignancy but his is extremely unlikely at the low doses used in uveitis. Other side-effects are rare.

Used properly and with safety monitoring with blood tests, problems rarely arise. However, Azathioprine is a powerful drug. There is no drug useful for the treatment of uveitis that is entirely free of potential or actual side-effects. Every patient and every eye inflammation is different. The information above is indicated to give you a general picture on Azathioprine. Always ask the doctor or nurse in the clinic if you are unsure of, or want more detail on, any points in relation to your own eye problem and general health.

Disclaimer: Adapted from Manchester uveitis patient leaflet.