Leflunomide is a pyrimidine synthesis inhibitor that treats rheumatoid arthritis. It decreases the symptoms and signs, enhance physical function and blocks the development joints' structural damage. Leflunomide has a brand name Arava and belongs to the drug class Antirheumatics and Selective immunosuppressants. It operates by blocking the particular enzymes that cause abnormal growth or development of tissues. As an immunosuppressive, Leflunomide is a disease-modifying anti-rheumatic drug (DMaRD). Leflunomide is used in the treatment of rheumatoid arthritis, psoriatic arthritis and other types of auto-immune disease. Leflunomide works by inhibiting dihydroorotate dehydrogenase therefore reducing inflammation that causes pain, swelling and stiffness. Possible side effects of Leflunomide may include: fever, chills, body aches, flu symptoms, white patches, chest pain, dry cough, breathing difficulties, wheezing, pain when you urinate, pale skin, and easy bruising or bleeding among others. Inform your doctor if you have some of those side effects as soon as possible. If you have allergies also, let your doctor know because Leflunomide contains inactive ingredients, which causes allergic reactions or other problems. Leflunomide can make you feel dizzy. Avoid driving or using machinery.