Introduction

This information is for people who have multiple sclerosis. It tells you about azathioprine, a treatment used to reduce relapses and disability in multiple sclerosis. It is based on the best and most up-to-date research.

Does it work?

We're not sure. If you have multiple sclerosis (MS), taking azathioprine tablets may reduce how many relapses you have. But it won't change how disabled you are by much. And azathioprine has serious side effects.

You should only be prescribed azathioprine tablets by a specialist. Preferably, you should get this medicine as part of a study.^[2] If you take azathioprine, you should have checks for side effects.

What is it?

Azathioprine (brand name Imuran) calms your immune system. This treatment was first used to stop transplanted organs being rejected by the body. Now it's used to treat many diseases that involve your immune system, including MS.

How can it help?

If you have MS and you take azathioprine tablets for a year or more, you'll probably have fewer relapses than if you didn't take them.^[58][59] The effects should last for at least two years.

How does it work?

No one knows exactly how azathioprine works in MS, but it affects several types of cells that cause inflammation in your body. So it might reduce the inflammation around your nerves. And this may help with the symptoms of MS. (To learn more about what happens in MS, see What is multiple sclerosis?)

Can they be harmful?

Yes, azathioprine tablets can have serious side effects.

Common side effects are stomach upset and skin rashes. About 1 in 10 people get side effects that they can't put up with and have to stop taking the drug.

The drug can also stop your bone marrow working properly. In particular, it may stop your bone marrow making enough white blood cells, which help your body fight off infections.^[58]

The most serious side effect of azathioprine is that, if you take it for a long time, it may increase your risk of cancer. People who take it for more than five years have a higher risk of cancer.^[60]

How good is the research on azathioprine?

We found two systematic reviews of research on using azathioprine tablets to treat multiple sclerosis (MS).^[58][59]

The studies found that people who took azathioprine were less likely to have a relapse. It wasn't clear whether treatment helped their level of disability.

These studies were all carried out a long time ago, so it is difficult to compare azathioprine with newer treatments for multiple sclerosis, such as interferon beta and glatiramer acetate.