RA is an inflammatory disease that causes pain, swelling, stiffness, and loss of function in the joints. It occurs when the immune system, which normally defends the body from invading organisms, turns its attack against the membrane lining the joints. RA is commonly managed by DMARDs initiated early in the disease process, before irreversible joint damage occurs. The most common DMARD prescribed in the United States is MTX; this drug is well tolerated and has better efficacy compared to other DMARDs, but is inadequate in providing lasting improvement in individuals with RA. In patients with an inadequate response to MTX alone, the use of biologic agents, including TNF-blocking agents in combination with MTX, has become a standard therapeutic approach.