Updated April 2024

What is Leflunomide?

Download button - information sheetLeflunomide (brand names Arabloc, Arava) is a medicine used to treat rheumatoid arthritis and psoriatic arthritis.

It is an immunosuppressive medicine, which means that it works by reducing the activity of the immune system.

In rheumatoid and psoriatic arthritis this action helps to reduce inflammation and thus reduces pain and swelling in the joints. It also limits damage to the joints and helps to prevent disability in the long term.

Because leflunomide acts to reduce the damage to the joints, rather than just relieve the pain, it belongs to the group of medicines called disease-modifying antirheumatic drugs (DMARDs).

Important things to remember

  • While taking leflunomide you must see your rheumatologist regularly to make sure the treatment is working and to minimise any possible side effects.
  • If you are worried about any possible side effects, you should contact your rheumatologist as soon as possible.
  • It is important to have regular blood tests as directed by your doctor.
  • If you are taking leflunomide and plan to become pregnant you must discuss the timing with your doctor.

What benefit can you expect from your treatment?

The majority of patients treated with leflunomide for rheumatoid and psoriatic arthritis find that their arthritis improves. For some, their arthritis symptoms are almost completely gone (remission). However, as everyone reacts differently to medicines, some may find that leflunomide does not help with their arthritis.

Leflunomide does not work straight away. It usually takes 4 to 8 weeks for symptoms to start to improve. The full effect may take up to 26 weeks.

Other medicines may be given to help with your symptoms while waiting for leflunomide to work.

How is leflunomide taken?

Leflunomide is taken by mouth as tablets. The usual dose is 10mg or 20mg once daily. Sometimes a higher dose may be given to start, but this may also mean side effects are more likely. Sometimes a lower dose is used such as 10mg every second day.

The tablets should be swallowed whole, not chewed or broken. They can be taken with or without food.

Can other medicines be taken with leflunomide?

Leflunomide may be used with other arthritis medicines including:

  • other DMARDs such as methotrexate
  • biological DMARDs (a newer type of DMARD, which helps reduce inflammation and joint damage)
  • steroid medicines such as prednisolone or cortisone injections into the joint
  • anti-inflammatory medicines (NSAIDs) such as naproxen (Naprosyn) or ibuprofen (Brufen, Nurofen)
  • pain medicines such as paracetamol.

How long is the treatment continued?

Treatment with leflunomide can be continued for more than 10 years as long as it is effective and no serious side effects occur.

If leflunomide treatment is stopped for more than a few weeks, there is a risk that your condition will worsen. Keep taking leflunomide unless advised by your doctor or unless side effects develop.

Are there any side effects?

You might experience side effects with your treatment. Tell your doctor if you are concerned about possible side effects.

If you do experience side effects, a lower dose may reduce side effects so that you can keep taking leflunomide. Your doctor will advise on any dose changes that are needed.

Most common possible side effects

  • Leflunomide may cause a dry mouth or mouth ulcers
  • Up to 20% of people experience stomach and bowel side effects when taking leflunomide. These effects can include excessive wind, bowel discomfort, loss of appetite, nausea (feeling sick) and diarrhoea. They often lessen after a few weeks of treatment; they may be reduced by drinking plenty of water.
  • Up to 10% of people may have other common side effects such as skin rash, reversible thinning of hair, increase in blood pressure or dizziness. These side effects are not usually serious and may lessen with continued treatment.

Less common or rare possible side effects

There are some rare but potentially serious side effects with leflunomide. These are more likely if leflunomide is being taken with methotrexate.

  • Blood counts: Leflunomide can cause a drop in the number of white blood cells, which are needed to fight infection. It can also cause a drop in the number of platelets, which help to stop bleeding. Regular blood tests aim to pick these problems up early when they occur. However, if you develop a sore mouth, mouth ulcers, easy bruising, nosebleeds, bleeding gums, breathlessness, infection or fever, tell your doctor straight away.
  • Infections: There is an increased risk of developing some infections, especially herpes zoster (chicken pox and shingles). You should try to avoid contact with people who have these infections. If you have symptoms of an infection, persistent fever or symptoms of COVID-19, tell your doctor straight away.
  • Liver tests: Leflunomide can cause liver tests to rise. These changes are usually mild and improve when the medicine is stopped or reduced. The effects on the liver do not usually cause symptoms unless the rise in liver tests is severe so regular blood tests are important. If you develop symptoms such as yellow discolouration of the whites of your eyes or yellow skin, tell your doctor straight away.
  • There have been rare reports of numbness (neuropathy) in patients taking leflunomide.
  • There have been rare reports of lung inflammation in patients taking leflunomide.

What precautions are necessary?

Blood tests

  • As leflunomide may affect liver and blood cells, you must have regular blood tests during your treatment. This is very important as you may not get symptoms with some of these problems in the early stages.
  • Blood tests are particularly important during the first few months of treatment and when leflunomide is taken with methotrexate.
  • As well as monitoring for side effects, blood tests help to monitor your condition to determine if the treatment is working.
  • You will need to have full blood counts and liver function tests every 2 to 4 weeks for the first few months of treatment and then every 1 to 3 months after that.
  • Your general practitioner (GP) will be informed about the monitoring schedule. It is important to see your GP if you have been asked to do so as they have an important role to play in monitoring your condition.

Use with other medicines

  • Leflunomide can interact with other medicines. You should tell your doctor (including your GP, rheumatologist and others) about all medicines you are taking or plan to take. This includes over-the-counter or herbal/naturopathic medicines. You should also mention your treatment when you see other health professionals.
  • In particular, leflunomide can interfere with phenytoin (for epilepsy) and warfarin (a blood thinning medicine).
  • If you are taking leflunomide, it is recommended you should not be immunised with ‘live’ vaccines such as MMR (measles, mumps and rubella), BCG (Bacillus Calmette Guerin), OPV (oral polio vaccine), or yellow fever. Talk with your rheumatologist before receiving any vaccines.

Use with alcohol

  • Because leflunomide can affect your liver, you should avoid heavy alcohol use while taking it.
  • It is not known what level of drinking is safe when on leflunomide. However, 1 to 2 standard drinks taken once or twice a week is unlikely to be a problem.
  • It is best to avoid having more than 4 drinks at one time, even if it doesn't happen often.


  • Your surgeon will discuss with you if you should stop leflunomide before or after surgery. Current guidelines suggest that leflunomide does not need to routinely be stopped around the time of surgery.

Use in pregnancy and breastfeeding

  • Leflunomide should not be taken during pregnancy or when breastfeeding.
  • If you are a woman of childbearing age you should use effective contraception while taking leflunomide.
  • Because the medicine stays in the body for a long time, you should not conceive for 2 years after stopping treatment. If a couple wishes to conceive, in certain cases, leflunomide can be ‘washed out’ from the body using other medicines.
  • It is not known if it is safe for men wanting to father a child to take leflunomide. Some experts advise leflunomide be stopped and ‘washed out’ in this case.
  • More detailed information is available here.

How to store leflunomide?

  • Store leflunomide in a cool, dry place, away from direct heat and light (e.g. not in the bathroom).
  • Keep all medicines out of reach of children.