BMA Concise Guide to Medicine & Drugs

Azathioprine

Brand name Imuran

Used in the following combined preparations None

QUICK REFERENCE

Drug group Disease-modifying antirheumatic drug and immunosuppressant drug

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Azathioprine is an immunosuppressant drug used to prevent immune-system rejection of transplanted organs. It is also used to modify, halt, or slow the underlying disease process in severe rheumatoid arthritis (see Antirheumatic drugs) that has failed to respond to conventional drug therapy.

Autoimmune and collagen diseases (including polymyositis, systemic lupus erythematosus, myasthenia gravis, and dermatomyositis) may be treated with azathioprine, usually in combination with corticosteroids.

Azathioprine is administered only under close supervision because of the risk of serious adverse effects. These include suppression of the production of white blood cells, thereby increasing the risk of infection as well as the risk of excessive or prolonged bleeding.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, injection.

Frequency and timing of doses Usually once daily with or after food.

Dosage range Initially according to body weight and the condition being treated and then adjusted according to response.

Onset of effect 2–4 weeks. Antirheumatic effect may not be felt for 8 weeks or more.

Duration of action Immunosuppressant effects may last for several weeks after the drug is stopped.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose Take as soon as you remember, then return to your normal schedule. If more than 2 doses are missed, consult your doctor

Stopping the drug Do not stop the drug without consulting your doctor. If taken to prevent graft transplant rejection, stopping treatment could provoke the rejection of the transplant.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause nausea, vomiting, abdominal pains, and diarrhoea. Notify your doctor.

POSSIBLE ADVERSE EFFECTS

The most common adverse effects of azathioprine are nausea, vomiting, loss of appetite, hair loss, and weakness. The drug may also cause unusual bleeding or bruising (which may be a sign of reduced levels of platelets in the blood), jaundice, rash, and fever or chills; if any of these symptoms develop, contact your doctor immediately. Also, if jaundice, rash, fever, or chills occur, the drug should be stopped.

INTERACTIONS

Allopurinol This drug increases the effects and toxicity of azathioprine; dosage of azathioprine will need to be reduced.

Warfarin Azathioprine may reduce the effect of warfarin.

Co-trimoxazole, trimethoprim, mesalazine, olsalazine and sulfasalazine These drugs may increase the risk of blood problems if taken with azathioprine.

Corticosteroids may increase the risk of infections and bowel problems.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have long-term liver or kidney problems.

· You have had a previous allergic reaction to azathioprine or 6-mercaptopurine.

· You have recently had shingles or chickenpox.

· You have an infection.

· You have a blood disorder.

· You are taking other medicines.

Pregnancy Azathioprine has been taken in pregnancy without problems. Discuss with your doctor.

Breast-feeding A small amount of the drug passes into the breast milk. Discuss with your doctor.

Infants and children No special problems.

Over 60 Increased likelihood of adverse effects. Reduced dose necessary.

Driving and hazardous work Avoid such activities until you have learned how azathioprine affects you because the drug can cause dizziness.

Alcohol No known problems.

PROLONGED USE

Prolonged use of this drug may reduce bone marrow activity, leading to a reduction of all types of blood cells. Some people have a genetic susceptibility to this effect. There is also a small increase in the risk of cancers affecting the immune system. Avoiding exposure to sunlight may help to prevent adverse skin effects.

Monitoring Regular checks on blood chemistry and blood cell counts are carried out.