Therapeutic drug monitoring of inununosuppressant drugs in clinical practice

Background: Therapeutic drug monitoring (TDM) is essential to maintain the efficacy of many immunosuppressant drugs while minimizing their toxicity. TDM has become more refined with the development of new monitoring techniques and more specific assays. Objective: This article summarizes current data on TDM of the following immunosuppressant drugs used in organ transplantation: cyclosporine, tacrolimus, sirolimus, everolimus, and mycophenolate mofetil. Methods: Published data were identified by a MEDLINE search of the English-language literature through March 2001 using the terms therapeutic drug monitoring, cyclosporine, tacrolimus, sirolimus, everolimus, and mycophenolate mofetil. Relevant conference abstracts were also included. Results: TDM of cyclosporine has been well studied, and recent findings indicate that monitoring of drug levels 2 hours after dosing is a more sensitive predictor of outcome than trough (C-0) monitoring. C-0 levels are being used more widely in TDM of tacrolimus; however, the relationship between C. and area under the curve has varied widely in clinical trials, with correlations ranging from 0.11 to 0.92. The use of TDM of sirolimus, everolimus, and mycophenolate mofetil is evolving rapidly. Conclusions: TDM of immunosuppressant drugs that have a narrow therapeutic index is an increasingly useful tool for minimizing drug toxicity while maximizing prevention of graft loss and organ rejection.