For immunosuppressive drugs the most accurate estimate of drug exposure is provided by the dose-interval area under the concentration vs time curve (AUC) at steady-state. Since the most accurate determination of the dose-interval AUC is obtained using a full set of timepoints throughout the dose interval involving usually from approximately 8 to 12 or more timed samples, this approach is not practical for routine clinic patients, or for newly transplanted inpatients nor for patients enrolled in clinical studies. Thus the importance of establishing in the most rigorous manner possible limited sampling strategies (LSS) for reliable estimation of the immunosuppressant drug AUC is both an important scientific and practical challenge. In this presentation a description of our approach and experience in developing LSS models for mycophenolic acid AUC estimation will be provided. Included in this presentation will be description of a cross-validation approach to developing the estimation models using the general linear model procedure in the statistical program SAS. The discussion will focus on our recent experience in developing LSS models for MPA AUC estimation in patient receiving either concomitant CsA or sirolimus.

Keywords: immunosuppressive drugs, Mycophenolic Acid, pancreati