Chapter 34: Rheumatoid Arthritis – Pharmacologic Therapy

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune inflammatory disease characterized by symmetric polyarthritis, typically impacting the small joints of the wrists and hands, though larger joints may also be affected. Pathophysiology involves a cascade of immunologic events where specific T-cell activation leads to the release of proinflammatory cytokines, notably tumor necrosis factor (TNF) alpha, interleukin (IL)-1, and IL-6, causing massive synovial tissue proliferation and the erosion of cartilage and bone. The definitive diagnosis utilizes the 2010 ACR/EULAR classification criteria, which evaluates joint involvement, serologic evidence such as rheumatoid factor (RF) or anticitrullinated protein antibody (ACPA), acute phase reactants like C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR), and symptom duration. The key therapeutic goal is to achieve and maintain remission or low disease activity, necessitating the early initiation of disease-modifying antirheumatic drugs (DMARDs) to halt joint destruction. DMARDs are subdivided into conventional synthetic (csDMARDs, including methotrexate, leflunomide, and sulfasalazine), targeted synthetic (tsDMARDs, such as Janus Kinase inhibitors), and biologic agents (bDMARDs). While nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids are useful for bridging symptomatic relief during acute flares or treatment initiation, they lack disease-modifying characteristics. Methotrexate is often the first-line therapy but carries serious risks like hepatotoxicity and pneumonitis, requiring rigorous baseline and ongoing laboratory monitoring. Specialized agents such as TNF-alpha inhibitors (e.g., etanercept), IL-6 receptor antagonists (e.g., tocilizumab), and T-cell costimulation modulators (e.g., abatacept) target specific pathways in the inflammatory process, but mandate screening for latent infections like tuberculosis before administration. Treatment management must also consider special populations, as many crucial DMARDs, including methotrexate and leflunomide, are strictly contraindicated in pregnancy.