Nephrotoxicity of immunosuppressive drugs: long-term consequences and challenges for the future.

The calcineurin inhibitors cyclosporin A (CsA) and tacrolimus (FK506) are associated with dose- and efficacy-limiting adverse events, including nephrotoxicity, which may diminish their overall benefits for long-term graft survival. Nephrotoxicity is difficult to distinguish from chronic allograft rejection and is a particular problem in the setting of renal transplantation. Minimizing immunosuppressant-induced nephrotoxicity could improve long-term renal allograft survival. However, to obtain significant long-term improvement in renal allograft outcomes, it may be necessary to adopt new immunosuppressive regimens that rely less on calcineurin inhibitors. Recipients of other transplanted organs, as well as patients with autoimmune diseases who require immunosuppressant therapy, could also benefit from this change in immunosuppressive drug strategy because their healthy, native kidneys are particularly susceptible to the nephrotoxic effects of CsA and FK506. CsA- and FK506-sparing regimens, which use reduced doses of CsA and FK506 in combination with other nonnephrotoxic immunosuppressants, may be the best current option for reducing nephrotoxicity. The chemical immunosuppressant mycophenolate mofetil (MMF) has been used as part of CsA- and FK506-sparing regimens that provide improved renal function while maintaining adequate immunosuppression. Such regimens should reduce patient morbidity and mortality. Also, because immunosuppressant-induced nephrotoxicity has been associated with significant financial costs, CsA- and FK506-sparing regimens should result in substantial savings in health care costs.