A 25-year-old woman develops painful swelling of both hands and wrists. She is also very stiff in the morning. Physical examination reveals erythema, swelling and joint line tenderness of the proximal interphalangeal, MCP, and wrists joints. Her RF is positive, ANA is negative, and x-rays of the hands show early erosive joint changes. Which of the following medications is most likely to prevent progression of disease?

Methotrexate, 7.5-20 mg once weekly, is the most commonly recommended disease modifying drug, because its effect is more rapid and patients are able to tolerate it for longer periods of time. Maximum improvement with methotrexate occurs after 6 months of therapy. Toxicity includes GI upset, oral ulceration, and liver function abnormalities. GI upset in particular may be ameliorated by concurrent folic acid administration. Pneumonitis has also been reported.