Prograf, generically known as tacrolimus, is a potent immunosuppressive medication primarily used to prevent organ rejection in patients who have undergone organ transplants, such as liver, kidney, or heart transplants. It works by inhibiting the activity of certain cells in the immune system that would normally attack the transplanted organ. Prograf does this by binding to specific proteins inside immune cells, thereby suppressing the immune response and helping to protect the new organ from rejection. It is typically administered orally or intravenously and requires careful monitoring of blood levels to ensure therapeutic effectiveness while minimizing potential side effects, which can include increased susceptibility to infections, high blood pressure, kidney problems, and diabetes, among others. Due to its critical role in transplant medicine, Prograf is a cornerstone in the management of transplant patients, helping to extend the life and improve the quality of life for those who have received organ transplants.