In cases where an essential organ fails and it is not possible to restore its function, a transplant often provides the only chance of survival. The progress made in transplant medicine and the improvement in the quality of life. is not only due to improved surgical techniques but also to the development of new immunosuppressants that prevent organ rejection. Currently, the standard of care for the prevention of organ rejection is a combination of immunosuppressive drugs, aimed at lowering the reactivity of the immune system enough to avoid rejection and to allow the organism to defend to the infections. The treatment is administered throughout the entire life of the transplanted organs.