Xeljanz XR (tofacitinib extended-release) is a Janus kinase (JAK) inhibitor prescribed for the treatment of moderate to severe rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis in adults. It works by inhibiting enzymes (JAKs) involved in the inflammatory process, thereby reducing immune system overactivity that causes joint damage and inflammation. Xeljanz XR is taken orally once daily, providing a convenient extended-release formulation that maintains steady medication levels. Patients using Xeljanz XR should be monitored for infections, blood clots, and other potential side effects. Common side effects include upper respiratory infections, headaches, and gastrointestinal symptoms. Treatment should be guided by a healthcare provider.