Baricitinib is an oral medication classified as a Janus kinase (JAK) inhibitor used mainly for the treatment of moderate to severe rheumatoid arthritis in adults who have not responded adequately to other therapies. It works by blocking specific enzymes involved in the inflammatory process, thereby reducing pain, swelling, and joint damage associated with autoimmune conditions. Baricitinib has also been used in certain cases for conditions such as severe COVID-19 and alopecia areata, where controlling immune system overactivity helps improve patient outcomes.