Leflunomide is a pyrimidine synthesis inhibitor belonging to the disease-modifying anti-rheumatic class of drugs (DMARD) used to treat symptoms of rheumatoid arthritis. 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 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. 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. What is this medication? LEFLUNOMIDE (le FLOO na mide) treats the symptoms of rheumatoid arthritis. It works by slowing down an overactive immune system. This decreases inflammation. It belongs to a group of medications called DMARDs. 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. 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 (Larava) is a disease-modifying anti-rheumatic drug (DMARD) used to treat rheumatoid arthritis and psoriatic arthritis. Learn about the side effects of leflunomide, from common to rare, for consumers and healthcare professionals. Leflunomide (LEF) is a nonbiological disease-modifying antirheumatic drug (DMARD) that has antiinflammatory and immune modulatory characteristics. LEF is approved by the US Food and Drug Administration (FDA) to treat rheumatoid arthritis (RA).