Updated February 2023

What is leflunomide?

Download button - information sheetLeflunomide is a medication which works by reducing the activity of the immune system. Rather than just relieving pain it acts to reduce the damage to the joints. It belongs to the group of medications called disease modifying antirheumatic drugs (DMARDs). Other DMARDs commonly used in Juvenile Idiopathic Arthritis are methotrexate, hydroxychloroquine, sulfasalazine.

It works on the white blood cells, which are part of the inflammatory process, which causes the pain and swelling of joints in arthritis.

Important things to remember

  • You must see your rheumatologist regularly to make sure the treatment is working and check for possible side effects.
  • You should have regular blood tests as suggested by your rheumatologist.
  • If you are worried about any side effects, you should contact your rheumatologist as soon as possible.
  • If you stop leflunomide for any reason, you must contact your rheumatologist.

How will it help?

It has been shown to reduce joint damage caused by inflammation, but it is a medication that works slowly. You can expect your child to start feeling better, but it might take one to two months.

How is leflunomide given?

Leflunomide is taken by mouth in tablet form and can be taken with or without food. If tablets cannot be swallowed whole, they can be crushed and taken with a chocolate spread or jam.

When should it be given?

Leflunomide is usually taken daily in tablet form.

What is the dose?

This depends on the weight of your child. 

How long will it be used for?

Treatment with leflunomide can continue long term to maintain control of arthritis.

Are there any side effects?

Leflunomide is usually very effective in improving your child’s condition, but as with all medications side effects can occur. Some are common, and some are rare. Most people don’t have any problems when they take leflunomide. Regular blood tests are important to monitor side effects.


Most common side effects


Nausea (feeling sick) vomiting, loss of appetite & diarrhoea

  • Anti-emetics (anti-sickness medication)

Skin rash/sun sensitivity

  • Use high factor sunscreen and hats

Mouth ulcers

  • Adjust dose

Rare side effects


Low blood cell count High blood pressure

Abnormal liver/kidney function

Allergic reactions and serious skin reactions

  • Usually improves if leflunomide dose is reduced or stopped



Things you need to know when your child is taking this medication

What to do if your child is sick
It is safe to give leflunomide if your child has a mild cold or cough. Don’t give leflunomide if your child:

  • Has a high fever
  • Has had vomiting/diarrhoea  
  • Has been in contact with chickenpox
  • Is sick and you’re not sure why.

If you’re not sure, talk to your doctor and get them checked if necessary before giving leflunomide.

Leflunomide can interact with other medications, including over-the-counter and herbal /naturopathic medications.
Always discuss any new medication with your doctor before taking it. Other medications, such as paracetamol (pain reliever), non-steroidal anti-inflammatory drugs (NSAIDs), and most antibiotics, can be taken with leflunomide.

Most immunisations are safe to have (flu vaccine, cervical cancer vaccine, killed polio vaccine (IPV) etc) when taking this medication.
Live virus vaccines (such as mumps, measles, rubella (MMR), polio (OPV)), varicella (chicken pox) and some live vaccines should not be used.

As Leflunomide affects the immune system and can affect the body’s ability to fight infections, contact with adults and children who have contagious illnesses like chickenpox should be avoided where possible. You should report any sign of infection, e.g. fever, to your child’s doctor. Leflunomide can make chickenpox infections more serious. A blood test can be done to see if your child is already immune to chickenpox. If your child is in contact with chickenpox or shingles, call your doctor.

Leflunomide and alcohol are both broken down by the liver. Drinking alcohol while you are on this medication can put extra strain on the liver. It is not known how much is safe, so it is suggested that anyone on leflunomide should avoid drinking alcohol.

Sexual health and pregnancy 
Leflunomide does not appear to affect fertility, but it may cause a miscarriage or increase the risk of birth defects to the unborn child. For any patient who is sexually active, it is important that adequate contraception is used during treatment and for at least two years after leflunomide has been stopped. If pregnancy occurs while taking leflunomide contact your doctor straight away.

Myths and misconceptions
You may hear a lot of different information about leflunomide from friends, pharmacists or people that you know. If you are worried about anything, please talk to your child’s doctor or nurse. If your child is taking leflunomide they should see their paediatric rheumatologist regularly to make sure the treatment is working and to minimise any possible side effects.