What is leflunomide and how is it used?

Leflunomide is a disease modifying anti-rheumatic drug (DMARD). It’s used to treat inflammatory conditions, such as:

It may take a while to start working, but once it does, it should help reduce the impact of your condition on your daily life and prevent any more damage to your joints.

Like all DMARDs, leflunomide slows down how active your condition is, rather than just treating the symptoms.

It regulates your immune system. When it’s working properly, your immune system protects you by fighting off infection and illness. But in autoimmune conditions like rheumatoid arthritis, psoriatic arthritis, and giant cell arteritis, the immune system attacks parts of your body by mistake.

Over time, leflunomide can reduce the inflammation that makes your joints painful, swollen and stiff.

When you’re first prescribed leflunomide, your rheumatologist (roo-ma-tolo-jist) will monitor your progress. Once they feel your condition has improved, your rheumatologist will probably ask your GP to manage your treatment and prescriptions.

You will not be prescribed 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.

Will I need any special checks before I take leflunomide?

You’ll need to have a blood test to check your blood cell count and make sure your liver is working properly before you start this treatment. You’ll also have your weight and blood pressure taken.

You will need to have these tests regularly, throughout your treatment. Initially, you’ll probably have to go for tests every couple of weeks until your dose has stabilised. Once your rheumatologist is happy with your results you will have less frequent monitoring. Your doctor will advise you on how often you’ll need to be tested.

You shouldn’t take leflunomide unless you’re having regular checks. Make sure all healthcare professionals you see – including doctors, dentists and nurses - know you’re taking leflunomide.

Is there anything that could stop me taking leflunomide?

Make sure you read the leaflet included with your medication before you start taking it. Some things might affect whether you can take leflunomide or not.

Tell your doctor if you:

  • have ever had problems with 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 ever had, or been in contact with someone with, tuberculosis (TB)
  • have a weak immune system or 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.

Birth control

Women of childbearing age should always use contraception while taking leflunomide. Talk to your doctor about which form would be best for you.

How is it taken?

For the first three days of the treatment, you’ll usually be given a high dose. This will then be dropped to a lower dose.

Once you’re on the lower dose, you’ll usually take leflunomide as a tablet once a day.

You can take your tablet with or without food, but it’s best to take it at the same time each day. You need to swallow it whole, rather than crushing or chewing it.

How long does it take to work?

It can take quite a while before you feel any effects from leflunomide. Usually it’s between four and six weeks before you’ll notice any changes and up to six months before it takes full effect.

Because it can take a while before you feel its full effects, you should carry on taking leflunomide:

  • even if it doesn’t seem to be working at first
  • even when your symptoms start to improve, as this will help keep your condition under control
  • unless you have severe side effects or become pregnant, in which case you should speak to your doctor as soon as possible.

Side-effects and risks

You may find your body adjusts to leflunomide without any side effects. Some people find it gives them loose bowel movements or diarrhoea (dy-a-ree-ah) but this usually settles down after a couple of weeks.

Other side effects 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 do 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.

Leflunomide reduces the amount of blood cells your body makes, which means you could pick up infections more easily.

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

  • a sore throat or fever
  • any unexplained bruising or bleeding
  • breathlessness
  • jaundice, when 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.

Chickenpox and shingles

You should also see your doctor if you come into contact with anyone who has chickenpox or shingles, or if you develop chickenpox or shingles yourself.

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.

Liver problems

Leflunomide can affect your liver.

You’ll have regular blood tests throughout your treatment to check for any changes in how your liver is working.

If you have any history of liver problems, you must tell your doctor before they prescribe you leflunomide. If you have a serious liver problem, it’s unlikely you’ll be prescribed leflunomide.


Talk to your doctor if you’re lactose intolerant or allergic to peanuts or soya. Some leflunomide tablets have a lactose coating. And some contain a substance called lecithin, which can be harmful to people allergic to peanuts or soya.

Skin reactions

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

What if I experience side effects?

Talk to your doctor or rheumatology nurse if you feel you’re experiencing side effects or a reaction to the treatment. If you have a bad reaction to leflunomide your doctor may suggest you stop the drug.

What if I have a bad reaction to leflunomide?

If your doctor thinks your reaction is serious they may suggest you have a washout treatment to remove the leflunomide from your body quickly.

A washout treatment consists of taking either 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.

You may have blood tests during the treatment to make sure the level of leflunomide in your body is dropping. If it doesn’t drop enough you will probably be given a second washout.

If you just stop taking leflunomide it can stay in your body for up to two years, unless you receive a washout treatment.

You will also be recommended to have a washout treatment to remove leflunomide from your body quickly if:

  • you become pregnant or want to start a family
  • you need to start another treatment which could interact with leflunomide.

What if I miss a dose?

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

What if I take too much leflunomide?

If you take too much, you may experience side effects. If you think you have taken too much leflunomide call your rheumatology team or the NHS helpline on 111 and ask for advice.

Effects on other treatments

Leflunomide can be prescribed alongside other drugs. However, some can interact badly with it. Examples include blood thinners warfarin and acenocoumarol (a-see-no-cum-a-rol), and the cancer treatment paclitaxel.

If you need to start any drugs that may interact with leflunomide, you may be offered a washout to remove the leflunomide from your system and an alternative treatment for your arthritis.

You should talk to your doctor before you start taking anything new and always tell any healthcare professional treating you that you are on leflunomide.

You should be able to continue taking non-steroidal anti-inflammatory drugs (NSAIDs) or painkillers if you need to. However, you should avoid taking over the counter or herbal remedies without first speaking to your healthcare team.


You should avoid live vaccines, such as yellow fever. However, in certain situations a live vaccine may be necessary, so speak to your doctor about this for their advice.

It’s a good idea to get the pneumococcal vaccine (new-mow-cok-al vak-seen), to protect you against the most common cause of pneumonia (new-mow-nee-a), and your yearly flu vaccines. These are both safe to have while you’re being treated with leflunomide, as they’re not live vaccines.

Can I continue taking leflunomide if I'm having an operation?

If you're going to have an operation, let your rheumatology team know and tell your surgical team you’re taking leflunomide. They may advise you to stop the leflunomide for a while before and after surgery.

Can I drink alcohol?

Leflunomide and alcohol can interact and damage your liver. You may be advised not to drink at all, or to only drink small amounts of alcohol.

Government guidelines say both men and women should have no more than 14 units of alcohol a week, and that you should spread these through the week rather than having them all in one go.

We would recommend you drink less than this but talk to your doctor if you’re in any doubt.

If you already have liver problems, you’ll probably be advised to avoid alcohol all together.

You can find out more about units of alcohol at www.drinkaware.co.uk.

Fertility, pregnancy and breastfeeding

Women taking leflunomide must use contraception and talk to their doctor or rheumatology team before planning for a baby.

Women who want to have a baby 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 do become pregnant while taking leflunomide, speak to your doctor or a member of your rheumatology team immediately. You will most likely be advised to stop taking leflunomide and have a washout treatment.

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

You are advised to avoid taking leflunomide until you have stopped breastfeeding, as 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.