Leflunomide was developed specifically to control inflammatory arthritis. It has been used since the early 2000s and is now a common treatment for RA.  


Leflunomide is a disease modifying anti-rheumatic drug (DMARD) developed specifically to control inflammatory arthritis. 

DMARDs act slowly, over weeks and months.  

Leflunomide is a prodrug, which means that it is inactive until it is taken. It is changed into the active drug inside the person’s own body.  

The overactive immune system in RA causes pain, swelling, heat and redness. Leflunomide dampens down this process by ‘switching off’ the cells responsible for this over-activity. It may also work in several other ways. 


Leflunomide has been used as a disease-modifying anti-rheumatic drug to treat rheumatoid arthritis since the early 2000s. Long-term clinical use, during which time it has been given to many people with RA, has shown it continues to be both effective and relatively safe.

Disease modifying drugs are used to treat inflammatory arthritis by decreasing joint inflammation and damage, reducing the risk of disability and enhancing quality of life.

Research into RA has found that the earlier the treatment starts with a DMARD to control the inflammation the better the long-term outcome.

How does it work?  

Leflunomide is only prescribed by a specialist experienced in the treatment of rheumatoid arthritis. A detailed medical history is very important to ensure the treatment is suitable for each patient. Blood tests are required beforehand and then usually every two weeks during the first six months of treatment and every eight weeks afterwards.

Leflunomide is prescribed as a tablet of 10mg or 20mg daily dependent on the clinical judgment of the specialist. Leflunomide was previously started with a three-day ‘loading dose’ of 100mg daily, but this has generally been stopped as it led to significant problems with diarrhoea.

Leflunomide acts on an enzyme in the body to limit the excessive reaction of the cells involved during inflammation, thereby reducing the swelling, pain and problems of RA.

Leflunomide persists for a long time in the body so that any change of treatment to a different drug must be carefully managed to avoid the potential that the side effects from both leflunomide and the next drug might cause problems. If necessary, leflunomide remaining in the body can be ‘washed out’ by giving a suitable substance such as activated charcoal over several days.

Most commonly reported side effects  

As with any medication, leflunomide has a number of possible side effects, although it is important to remember that these are only potential side effects and may not occur. Side effects may include:

  • A rise in blood pressure therefore regular monitoring is advised  
  • Alteration to some blood test results eg liver tests, full blood count  
  • Unexplained diarrhoea  
  • Skin reactions; inflammation of the lining of the mouth  
  • Increased susceptibility to infections  
  • Shortness of breath, cough  
  • Numbness/tingling of feet and/or hands  

More information on side effects can be found in the patient information leaflet for leflunomide, which will come with your medicine.  

Remember to report any concerns about possible side effects to the doctors, pharmacists or nurses.  

Leflunomide with other medicines  

  • Non-steroidal anti-inflammatory drugs (NSAIDs) and steroid treatment may be continued together with leflunomide  
  • The efficiency of oral contraceptives is not affected  
  • Monitoring of warfarin may need to be more frequent  
  • Caution is needed when leflunomide is prescribed alongside many other prescription medicines  

Leflunomide during pregnancy and breastfeeding  

Recommendations for women  

  • Leflunomide is suspected of causing birth defects  
  • Effective contraception is essential while taking leflunomide and for up to two years after stopping it, or for 11 days using a ‘wash out’ procedure. Blood tests are then required to check the levels of leflunomide and again at 14 days  
  • Your doctor’s advice is essential on exactly when contraception may be stopped  
  • Women must not take leflunomide whilst breast-feeding  

Recommendations for men  

  • Leflunomide is suspected of causing birth defects  
  • For men wanting to father a child reliable contraception is essential at least three months after stopping it or for 11 days using a ‘wash out’ procedure  
  • Blood tests are then required to check the levels of leflunomide and again at 14 days  
  • Your doctor’s advice is essential on exactly when contraception may be stopped  

Pregnancy information in this article is based on British Society for Rheumatology (BSR) guidelines on prescribing drugs in pregnancy and breastfeeding. Before starting a family it is recommended that you get advice from the consultant or clinical nurse specialist about when to start a pregnancy.

Leflunomide and alcohol  

The recommendation is that alcohol consumption should be avoided during treatment with leflunomide as there is the possibility of increased toxic effects on the liver.  

Medicines in rheumatoid arthritis

We believe it is essential that people living with RA understand why certain medicines are used, when they are used and how they work to manage the condition.