Influence of Sampling-Time Error on Cyclosporine Measurements Nominally at 2 Hours After Administration (Technical Briefs‪)‬

Cyclosporine (CsA) blood concentrations measured 2 h after Neoral[R] administration ([c.sub.2]) are a sensitive predictor of clinical outcome in organ transplantation, as suggested by a recent prospective clinical trial in liver transplant patients (1). [c.sub.2] is now recommended as the target exposure index for the therapeutic drug monitoring (TDM) of CsA (2-8). The aim of this study was to investigate, for different types of grafts, the concentration-time relationships around [c.sub.2] to evaluate the concentration error as a function of the sampling-time error and to identify the sampling-time range compatible with acceptable performance of this [c.sub.2] TDM strategy. Data obtained from three different clinical trials were studied retrospectively. Each patient gave written informed consent, and each trial was approved by a local ethics committee (9-11). The three populations were as follows: