Methotrexate is considered the first-line treatment for rheumatoid arthritis and has been used to treat the disease since the 1980s. It works by reducing inflammation and immune system activity. While its exact mechanism is unknown, it likely involves effects on T cells, B cells, and cytokines like TNF-α, IL-6, and IL-1. Common side effects include liver and kidney toxicity. Future research seeks to develop targeted drug delivery methods to increase effectiveness and reduce side effects. Methotrexate remains a cornerstone therapy for rheumatoid arthritis treatment.