Leflunomide (Arava) is a drug approved to treat adults with moderate to severe inflammatory arthritis (e.g. rheumatoid arthritis). It belongs to a class of medications called disease-modifying antirheumatic drugs (DMARDs), which aim to decrease inflammation and prevent further damage. Leflunomide (Larava) is a disease-modifying anti-rheumatic drug (DMARD) used to treat rheumatoid arthritis and psoriatic arthritis. Leflunomide is used to treat active rheumatoid arthritis. This medicine works by stopping the body from producing too many of the immune cells that are responsible for the swelling and inflammation. Overview: Leflunomide is an oral tablet used for rheumatoid arthritis. This medicine may help reduce joint swelling and damage. Common side effects include diarrhea, nausea, and headaches. Stop. Leflunomide is a pyrimidine synthesis inhibitor belonging to the disease-modifying anti-rheumatic class of drugs (DMARD) used to treat symptoms of rheumatoid arthritis. What is leflunomide? Leflunomide affects the immune system and reduces swelling and inflammation in the body. Leflunomide is used to treat the symptoms of rheumatoid arthritis. Leflunomide may also be used for purposes not listed in this medication guide. Leflunomide is an immunomodulatory drug that achieves its effects by inhibiting the mitochondrial enzyme dihydroorotate dehydrogenase (DHODH), which plays a key role in the de novo synthesis of uridine monophosphate (rUMP), which is required for the synthesis of DNA and RNA.