Azathioprine is a medication that suppresses the immune system. It is a Disease-Modifying AntiRheumatic Drug (DMARD) and belongs to a class of chemicals called purine analogues.
Azathioprine has been in use since the 1950s. It was originally developed to treat certain forms of cancer but has proven useful in treating numerous autoimmune disorders, as well as preventing organ rejection in transplant patients.
Rheumatologists use Azathioprine to treat (Systemic Lupus Erythematosus), as well as other types of arthritis and rheumatic diseases.
Azathioprine is available in 50 mg oral tablets.
The usual starting dose for Azathioprine is 50 to 100 mg per day (1 to 2 tablets).
The maintenance dose is based on body weight. The standard dose ranges from two tablets (100 mg) to four tablets (200 mg).
Azathioprine can be taken once or twice a day, as prescribed by a doctor.
Taking Azathioprine with food can help reduce possible stomach upset.
It takes 6 to 12 weeks for Azathioprine to start working. The maximum effect can take up to 6 months.
If a doctor changes the dose, it can take another 8 to 12 weeks to feel the effects. It is important for people starting this medicine to be patient and continue taking it as prescribed.
Important Tests and Risks
Patients taking Azathioprine should have their blood tested regularly (usually every 1 to 3 months as advised by their doctor).
It is important to make sure the medication is having no harmful effects on the liver, bone marrow, or blood counts.
Drinking alcohol while taking Azathioprine can harm the liver. Patients are advised to stop drinking alcohol, or at the very least, significantly limit their alcohol consumption.
Azathioprine can make it a bit harder for people to fight off infections.
People taking this medicine should call their doctor they have a fever, think they have an infection, or have been prescribed antibiotics to treat an infection.
Patients should coordinate with their doctor to stop treatment before any surgery. It can be re-started once things have healed and there’s no sign of infection.
Patients should discuss all vaccinations with their doctor because some are not advisable to get while taking Azathioprine.
The gout medications Zyloprim (allopurinol) and Uloric (febuxostat) can interact with Azathioprine.
Patients taking Azathioprine should tell their doctor if they are also taking Zyloprim or Uloric.
Azathioprine is a prodrug of mercaptopurine.
Prodrugs are drugs that convert inside the body into other active drugs. This means that after Azathioprine is taken, it is converted to the active drug mercaptopurine inside the body.
Mercaptopurine inhibits an enzyme that is required for the synthesis, or creation, of DNA.
This effect reduces the numbers of cells that can rapidly replicate in the body, including the immune system’s white blood cells: T-cells and B-cells. This effect also explains some of Azathioprine’s possible side effects because other types of cells can be impacted as well.
Although suppressing the immune system can make it slightly harder for patients to fight off infections, it also helps stabilizes an overactive immune system.
Patients suffering from rheumatic diseases like lupus or arthritis will notice a reduction in their symptoms as their immune system’s attack on their own body is lessened.
Side Effects of Azathioprine
Azathioprine is a medicine that requires regular blood tests to monitor for more serious side effects to the liver and bone marrow. Patients are advised to stop drinking alcohol while taking Azathioprine to help protect the liver.
MORE COMMON side-effects include:
- Nausea, vomiting, and diarrhea – Patients should tell their doctor if this happens
- Skin rash that may be itchy – Patients should let their doctor know if they develop a rash while taking Azathioprine
- Aching in the joints
RARE side-effects include:
- Hair Loss – Azathioprine rarely causes thinning of the hair. Patients should let their doctor know if this becomes a problem.
- Liver – Azathioprine may irritate the liver. This does not usually cause symptoms but can be found on blood tests. This is uncommon and any damage is usually reversible when patients are regularly monitored with monthly blood tests.
- Blood Counts – Azathioprine can cause a drop in the numbers of red blood cells (which carry oxygen), white blood cells (which are needed to fight infection) and platelets (which help to stop bleeding). Any changes in blood counts will be caught with regular blood tests.
- Infection – Any infections or fevers should be taken seriously and reviewed by a doctor.
- Malignancy – Malignancy – When used for long periods of time, Azathioprine may be associated with a small increased risk of skin or blood cancers.
How to minimize the side-effects of Azathioprine:
- Patients should take Azathioprine as prescribed and get regular blood tests
- Patients should attend all doctor appointments
- Taking Azathioprine with food helps reduce possible stomach upset
- Patients should avoid alcohol while taking Azathioprine
Patients should talk to their doctor if they are concerned about any side effects.
Azathioprine can safely be stopped without needing to be weaned off. However, rheumatic diseases can “flare” after the medicine is stopped.
Azathioprine is felt to be safe in pregnancy. However, anyone who becomes pregnant while taking Azathioprine should let their doctor know.
People who should NOT be taking Azathioprine include:
- Patients who have had a previous reaction to Azathioprine
- Men who are planning pregnancy with their partner
- Some patients with diseases of the liver, kidney, or blood disorders
- Patients with active infections
People taking Azathioprine should call their doctor if they feel sick and want to stop, or they are concerned about any side effects.
Other reasons to call a doctor while taking Azathioprine include:
- Nausea or diarrhea
- Fever or possible infection
- Stomach pain or noticing yellowing of the skin
- Becoming pregnant or planning pregnancy
- Before any surgery
Watch Dr. Andy Thompson, a Canadian rheumatologist, introduce Azathioprine in this short video: