What is leflunomide?

Leflunomide is a disease modifying anti-rheumatic drug (DMARD). It's also known by its brand name Arava.

It's used to treat:

It may take four to six weeks before you start to feel the effects of leflunomide on your symptoms. It can take four to six months to feel the full effect of the drug.

In conditions like rheumatoid arthritis and psoriatic arthritis, the immune system attacks parts of your body by mistake. Leflunomide can dampen down the activity of the immune system. This can reduce the inflammation that makes your joints painful, swollen and stiff.

Because it's a long-term treatment, you should carry on taking leflunomide:

  • 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.

You'll be prescribed leflunomide by a consultant rheumatologist.

Who can take leflunomide?

You will not be prescribed leflunomide if:

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

There are some other things that might affect whether you can take leflunomide. Tell your doctor if you:

  • have ever had problems with your liver, because leflunomide can seriously affect your liver
  • are taking any other prescription or over-the-counter medications
  • are taking any herbal remedies or supplements
  • have a severe infection
  • have had kidney problems
  • have nerve damage
  • have any history of tuberculosis (TB)
  • have a weak immune system
  • have any history of bone-marrow problems
  • have ever had an allergic reaction to a drug
  • have been told by a doctor you have low numbers of proteins in your blood.

How is leflunomide taken?

You will need to swallow leflunomide tablets with water, and you can take them with or without food. It’s important to swallow them whole and not chew them or crush them. It’s best to take your leflunomide at the same time each day.

If you miss a dose, take your tablet as soon as you remember unless it’s almost time for your next one. If you miss a dose of leflunomide, don’t take any more than your regular dose to make up for it.

If you take too much of your medication you may experience diarrhoea, stomach pain, pale skin, bruising or bleeding, dark urine, or yellowing of the skin or eyes, caused by jaundice.

If you think you have taken too much of your leflunomide and feel unwell call NHS111 and ask for advice, or if you’re feeling very unwell go to your local accident and emergency department.

If you're sensitive to lactose, peanut or soya, speak to your doctor before taking leflunomide, as it contains extracts of these allergens.

Side effects and risks

You may not have any side effects from taking leflunomide. Some people find it gives them loose bowel motions or diarrhoea, but this usually settles down after a couple of weeks.

Other side effects can include:

  • feeling sick
  • mouth ulcers
  • weight loss
  • stomach pain
  • unusual tiredness
  • headaches
  • dizziness
  • weakness or pins and needles
  • dry skin or a rash
  • a slight rise in blood pressure.

Some people experience hair loss, but this is quite rare and usually minor.

Speak to your doctor or rheumatology nurse as soon as possible if you experience any of these side effects or any other changes that concern you. If your side effects are serious, you may need to stop the drug and have a washout treatment. 

Washout treatment involves taking activated powdered charcoal or a drug called cholestyramine (co-la-sti-ra-meen) for 11 days. These should rapidly flush the leflunomide out of your body.

If you have psoriasis and find your skin becomes inflamed, irritated or infected once you’ve started taking the drug, speak to your doctor.

If you develop shortness of breath and a dry cough after starting the leflunomide, you should also speak to your doctor.

Speak to your doctor if you come into contact with anyone who has chickenpox or shingles, or if you develop chickenpox or shingles. Because leflunomide reduces the amount of blood cells your body makes you may pick up infections more frequently. These viruses can affect you badly when you're taking leflunomide. You may need antiviral treatment, and your leflunomide may be stopped until you’re better.

Before you start leflunomide you will have the following tests:

  • a full blood count
  • a liver function test
  • a kidney function test
  • your blood pressure will be checked
  • a chest X-Ray.

Once you've started taking leflunomide, you'll need to have these tests every two weeks. When you get settled on the drug, you will still need to have the tests, but not so often.

Tell your doctor or rheumatology nurse if you develop any signs of infection, such as:

  • a sore throat or fever
  • any unexplained bruising or bleeding
  • breathlessness
  • jaundice, where the eyes and skin turn yellow
  • any other symptoms that worry you.

Tips to reduce your risk of infection

  • Try to avoid close contact with people you know have an infection.
  • Wash your hands regularly and carry around a small bottle of antibacterial hand gel.
  • Keep your mouth clean by brushing your teeth regularly.
  • Stop smoking if you’re a smoker.
  • Make sure your food is stored and prepared properly.
  • Try to keep your house clean and hygienic, especially the kitchen, bathrooms and toilets.

Carrying an alert card

It’s recommended that you carry a biological therapy alert card so anyone treating you will know that you’re on leflunomide. Ask your rheumatology team for a card.

Effects on other treatments

Leflunomide can be prescribed alongside other drugs, but some – such as the blood thinners warfarin and acenocoumarol and the cancer treatment paclitaxel – can interact badly with it.

If you need to start these treatments, you may be offered an alternative treatment for your arthritis and a washout to remove the leflunomide from your system.

You should talk to your doctor before you start taking anything new and always tell any new healthcare professional who treats you that you're on leflunomide.

Unless your doctor advises against it, you can carry on taking non-steroidal anti-inflammatory drugs (NSAIDs) or painkillers if needed.

Don’t take over-the-counter or herbal remedies without first speaking to your healthcare team.


It’s usually recommended that people on leflunomide avoid live vaccines such as measles, mumps and rubella (MMR), chickenpox and yellow fever. But sometimes a live vaccine may be necessary, so you should discuss this with your rheumatology team.

If you’ve never had chickenpox, it’s a good idea to get a vaccination against it before starting leflunomide. But discuss this with your rheumatology team first. 

It’s also a good idea to get any family or household members vaccinated against chickenpox before you start taking leflunomide. 

The Zostavax shingles vaccine is a live vaccine and isn’t recommended for people who are on leflunomide. However, a non-live shingles vaccine (Shingrix) is available so you may be able to have this instead.

It’s recommended you have vaccinations against COVID-19. It’s also recommended you have the pneumonia (new-moh-nee-uh) vaccine and the yearly flu vaccine injection while taking leflunomide. These vaccines are not live, so it’s safe for you to have them.

Having an operation

If you're going to have an operation you may be advised to stop the leflunomide for a time before and after surgery. Talk to your healthcare team about this.

Can I drink alcohol?

Leflunomide and alcohol can interact and affect your liver.

It's recommended that you only drink small amounts of alcohol when taking leflunomide, or that you don't drink alcohol at all.

As a guide, you shouldn't drink more than four units of alcohol a week while taking leflunomide.

A standard glass of wine is two units, and a pint of beer is between two and three units.

If you've ever had problems with your liver, you'll probably be advised to avoid alcohol all together.

Talk to your healthcare team if you have any concerns.

Fertility, pregnancy and breastfeeding

Women taking leflunomide must use contraception, and talk to their rheumatology team before trying for a baby.

You will be advised to stop taking leflunomide and have a washout treatment before trying to become pregnant. You’ll usually be advised to carry on using contraception until blood tests show the drug is completely out of your system.

If you prefer not to have the washout treatment, you may be advised to continue using contraception for up to two years after stopping leflunomide.

If you become pregnant while taking leflunomide, speak to your doctor or a member of your rheumatology team immediately. You will probably be advised to stop taking your leflunomide and have a washout treatment as soon as possible.

If this happens to you, it’s unlikely that leflunomide will harm your baby if you act quickly and contact your rheumatology team.

You are advised to avoid taking leflunomide until you have stopped breastfeeding because it may pass into your milk.

Men should be fine to take leflunomide if they are trying for a baby with their partner, but the research is limited so you should discuss this with your doctor.