Used primarily in immunosuppressive therapy, especially to prevent organ rejection following transplantation such as liver, kidney, or heart. It works by inhibiting T-cell activation through suppression of cytokine production, particularly interleukin-2. Commonly formulated in oral capsules and intravenous solutions for systemic use. Also available in topical formulations for the treatment of atopic dermatitis, where it modulates local immune response without the side effects associated with corticosteroids. Its potent mechanism makes it valuable in managing autoimmune skin conditions and in patients who are intolerant to steroid-based treatments. Due to narrow therapeutic index, blood concentration monitoring is required to ensure efficacy and minimize toxicity.