What is leflunomide and how is it used?

In some inflammatory conditions, including rheumatoid arthritis and other autoimmune diseases, the body’s immune system is overactive. Leflunomide regulates the activity of the immune system, and modifies the underlying disease process, rather than simply treating the symptoms.

It’s not a painkiller, but in time it can reduce the inflammation that causes pain, swelling and stiffness in the joints. It may be six weeks or more before you start to notice any benefit, and as long as six months before you feel the full effect.

Leflunomide can be used for rheumatoid arthritis, psoriatic arthritis and other autoimmune diseases. Your consultant rheumatologist will prescribe leflunomide at first and monitor how you get on with it. Then, after a time, your GP will probably take on the monitoring and issue further prescriptions.

Your doctor may decide not to prescribe, or to stop, leflunomide if:

  • you’re pregnant or breastfeeding, or planning to have a baby soon
  • you have severe side-effects or need to start another treatment that could interact with leflunomide.

You’ll need to have a blood test and blood pressure measurement before you take leflunomide, and regular blood tests and blood pressure checks when you’re taking it. You may be asked to keep a record booklet with your test results in it, and take it to any GP or hospital visits.

You should not take leflunomide unless you’re having regular checks.

When and how do I take leflunomide?

Leflunomide is taken in tablet form once a day. Swallow the tablets whole without crushing or chewing them. It’s best to take them at the same time every day, with or without food. Your doctor will tell you what dose to take – it’s usually either 10 or 20 mg a day.

Because it’s a long-term treatment it’s best to keep taking leflunomide (unless you have severe side-effects):

  • even if it doesn’t seem to be working at first
  • even when your symptoms start to improve (to help keep your condition under control).

Possible risks and side-effects

The most common side-effects are:

  • diarrhoea
  • feeling sick (nausea)
  • mouth ulcers
  • weight loss
  • stomach pain
  • headaches
  • dizziness
  • weakness
  • pins and needles
  • dry skin
  • rashes
  • hair loss (rare and usually minor)
  • slight rise in blood pressure.

Leflunomide can affect the blood count by reducing the number of blood cells you make, which can make you more likely to develop infections. It can also affect the liver. You’ll have regular blood tests to check for early signs of these effects.

Tell your doctor or rheumatology nurse straight away if you develop any signs of infection such as a sore throat or fever, or have unexplained bruising, bleeding, a rash, breathlessness, unusual tiredness, stomach pain, jaundice (yellow eyes or skin), or any other new symptoms that concern you.

You should also see your doctor if you develop chickenpox or shingles or come into contact with someone who has chickenpox or shingles. These illnesses can be severe if you’re on leflunomide. You may need antiviral treatment, and your leflunomide may be stopped until you’re better.

Reducing the risk of infection

What else should I know about leflunomide?

Leflunomide may remain in the body for more than a year after you stop taking it. In some circumstances it’s recommended that leflunomide is eliminated from the body more quickly – for example if:

  • you become pregnant
  • you have severe side-effects
  • you need to start another treatment which could interact with leflunomide.

Your doctor may suggest having a ‘wash-out’ treatment to help remove leflunomide from your body. This involves taking a drug called cholestyramine for 11 days. You may have blood tests to check that the level of leflunomide in your body is falling.

Taking other medicines

Leflunomide may be prescribed alongside other drugs. However, you should discuss any new medications with your doctor, because some can interact with leflunomide.

Examples include warfarin (which thins the blood) and phenytoin (which is used in epilepsy). Always tell any doctor treating you that you are on leflunomide.

  • You can carry on taking a non-steroidal anti-inflammatory drug (NSAID) or painkillers if needed, unless your doctor advises otherwise.
  • Don’t take over-the-counter or herbal remedies without discussing this first with your healthcare team.


Leflunomide and alcohol may interact and damage your liver, so you should only drink alcohol in small amounts (no more than 4–8 units per week). Discuss this with your doctor or rheumatology nurse.


If you’re on leflunomide it’s recommended that you don’t have live vaccines such as yellow fever or shingles. However, in certain situations a live vaccine may be necessary, for example rubella immunisation in women of childbearing age. In these cases your doctor will discuss the possible risks and benefits of the immunisation with you.

Pneumococcal vaccine, which protects against the most common cause of pneumonia, and yearly flu vaccines are safe and recommended.

Having an operation

If you’re going to have an operation, discuss this with your healthcare team, who may advise you to stop the leflunomide for a time before and after surgery.

Fertility, pregnancy and breastfeeding

If you’re thinking of having a baby, we suggest you discuss your medications with your rheumatology team beforehand.

Based on limited research in human pregnancy, leflunomide doesn’t appear to be harmful. However, because the evidence is limited, both men and women taking leflunomide are advised to use contraception.

Women who want to have a baby are usually advised to stop taking leflunomide and have a wash-out treatment before trying to become pregnant (see ’What else should I know about leflunomide?’). If you prefer not to have the wash-out treatment, you may be advised to continue using contraception for up to two years after stopping leflunomide.

If you become pregnant while taking leflunomide, stop the drug and speak to your doctor as soon as possible about having the wash-out treatment. As long as you do both of these things it is very unlikely that leflunomide will have caused any harm to your baby.

As a precaution, men taking leflunomide may be advised to have the wash-out treatment before trying to father a child. Breastfeeding isn’t recommended if you’re on leflunomide because it may pass into the breast milk and could affect your baby.

Skip to content