Uveitis Information Group (Scotland)

Azathioprine

Azathioprine, also known as Imuran or Azasan, is one of the earliest immunosuppressant used with organ transplants. It works by suppressing the body's immune system and reduces the inflammation that accompanies immune reactions. In uveitis it is only used when it is necessary to control the immune system. This is mostly the case in Posterior uveitis, and rarely so in Anterior uveitis, unless an auto-immune disease is involved.

Azathioprine is usually supplied in tablet form, in combination with a second immunosuppressant. It is sometimes used in combination with steroids. The therapy may take some weeks or months to show noticeable results.

The advantage of combining two immunosuppressants is that it allows you to reduce the dose of steroids you are taking, (steroid-sparing effect), thus reducing the toxic effect that taking high dose steroids has on your body, when taken for a prolonged period. The theory is that with time your immune system will learn to respond normally.

BEFORE USING YOUR MEDICINE

Tell your doctor before you start taking Azathioprine if the answer to any of the following questions is yes:

• Do you suspect that you have had an allergic reaction to, or been upset by any of the ingredients in Azathioprine?
• Do you have any kidney problems or have you had any disease, which may have affected your kidneys?
• Do you have an infection of any type?
• Have you been told that you have any kind of tumour?
• Do you have any liver problems or have you had any disease, which may have affected your liver?
• Have you been told that you that you have gout?
• Are you taking any other medicines (either bought or prescribed)?

Some medicines can interfere with your treatment, so make sure to check with your doctor or pharmacist before taking any other medicines. In particular, tell your doctor if you are taking any of the following:

• Allopurinol/oxipurinol/thiopurinol
• Neuromuscular blocking agents
• Warfarin
• penicillamine
• co-trimoxazole
• Captopril
• Cimetidine
• Indomethacin
• Aminosalicylate derivatives (e.g. olsalazine, mesalazine or sulphasalazine)

Vaccines: Live vaccines should be avoided and there may be a poor response to killed vaccines.

Taking your Medicine

Your doctor will work out the correct dose of Azathioprine for you depending on your body weight In general, starting dosage is from 1 to 3 mg/kg bodyweight/day, and is adjusted, within these limits, depending on the clinical response (which may not be evident for weeks or months) and the blood tests.

Overdose

Unexplained infection, ulceration of the throat, bruising and bleeding are the main signs of over dosage with Azathioprine and result from bone marrow depression which may be maximal after 9 to 14 days. These signs are more likely to be manifest following chronic over dosage, rather than after a single acute overdose.

After taking your medicine

Most people benefit from taking this medicine, but a few people can be upset by it.

The dose of this medicine needs to be carefully adjusted by your doctor. Too much can affect the blood and the liver. You will, therefore, have regular blood tests and visits to the hospital or your GP. This will give you the chance to talk to your doctor about your treatment and mention any problems you are having.

First two months

Weekly blood tests are required as azathioprine may affect the production of blood cells by the bone marrow. It is suggested that during the first 8 weeks of therapy, complete blood counts, including platelets, should be performed weekly. Tell your doctor if you have any of the following symptoms:

• Feeling sick and/ or being sick
• Diarrhoea
• Fever, shivering/chill and skin rash
• Muscle and bone pain
• Kidney problems
• Tiredness, dizziness

Tell your doctor immediately if any of the following happen:

• You start to notice any signs of fever or an infection
• You have unexpected bruising or bleeding
• Your skin or the whites of your eyes turn yellow
• You develop a chest infection

Some patients experience nausea when first given Azathioprine. This appears to be relieved by administering the tablets after meals.

In the Long Run

• Reversible pneumonitis has been described very rarely.
• Hair loss has been described on a number of occasions in patients receiving azathioprine and other immunosuppressive agents. In many instances the condition resolved spontaneously despite continuing therapy. The relationship between alopecia and azathioprine treatment is uncertain.
• A rare, but life-threatening hepatic veno-occlusive disease associated with chronic administration of azathioprine has been described, primarily in transplant patients. In some cases withdrawal of azathioprine has resulted in either a temporary or permanent improvement in liver histology and symptoms.

Pregnancy and Breast Feeding

Azathioprine should not be given during pregnancy without careful assessment of risk versus benefit.

Azathioprine and/or its metabolites have been found in low concentrations in foetal blood and amniotic fluid after maternal administration of azathioprine.

Low counts of white cells (fight infections) of the blood and low count of platelets (help the blood clot) have been reported in a proportion of new borns, whose mothers took azathioprine during their pregnancies.

Extra care with regular blood tests is especially advised during pregnancy.

6-Mercaptopurine has been identified in the colostrum and breast-milk of women receiving azathioprine treatment.

What are the risks involved in taking this drug?

While you are taking steroids, you are more likely to develop illnesses due to infection. Also any existing infections may become worse resulting in septicaemia. This is especially so during periods of stress. Certain infections can be serious if not controlled.

If you want further information about the drug, Patient Plus Fact Sheet on Azathioprine (Patient UK) will give you more information about possible side effects but you have to bear in mind that it is written with transplant patients in mind rather than uveitis patients.