Which immunosuppression?

Sirolimus: continuing the evolution of transplant immunosuppression

OBJECTIVE

To review the pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and economic issues associated with sirolimus, the most recent immunosuppressive agent approved for kidney transplantation.

DATA SOURCES

A MEDLINE search (1966-June 2000) was completed to identify primary and review articles. In addition, abstracts from recent meetings on transplantation were reviewed for information and research on sirolimus.

STUDY SELECTION AND DATA EXTRACTION

Blinded, randomized, controlled studies were the goal, but, as with most newly approved immunosuppressive agents, a significant amount of information on sirolimus is not available in this optimal form. All articles were assessed and all pertinent information was incorporated in this review.

DATA SYNTHESIS

Sirolimus is structurally related to the immunosuppressive agent tacrolimus, and retains a pharmacokinetic and drug interaction profile similar to that of the calcineurin inhibitors, cyclosporine and tacrolimus. However, the novel mechanism of action of sirolimus differs significantly from these agents, as does its adverse effect profile. The most significant adverse reaction is hyperlipidemia. Clinical experience with sirolimus has allowed transplant centers to expand its use into other areas of transplantation as well as certain autoimmune disorders.

CONCLUSIONS

The definitive role of sirolimus will continue to be determined; however, sirolimus offers an excellent addition to the transplant immunosuppression armamentarium.

Steroid withdrawal in liver transplantation: benefits, risks, and unanswered questions

Since the early days of clinical liver transplantation, steroid therapy has constituted the mainstay of maintenance immunosuppression and is still currently combined with cyclosporine or tacrolimus worldwide. Nevertheless, the side effects of long-term steroid administration, particularly diabetes, hypercholesterolemia, arterial hypertension, infections, and bone diseases, including growth retardation in children, have focused the interest on the feasibility of steroid-free immunosuppression. The benefits and the risks of steroid withdrawal (SW) after liver transplantation are overviewed. In adults, early (3 months after transplantation) SW has been validated by several studies, whereas in pediatric recipients, the timing and selection criteria to optimize the risk/benefit ratio of SW still constitute a matter of debate. The identification of the unanswered questions in this field may serve as a framework for future studies to better assess steroid-free immunosuppression after liver transplantation.