Abbreviated cyclosporine AUCs on Neoral - the search continues!

Cyclosporine is a powerful immunosuppressant with a narrow therapeutic window and considerable inter- and intrapatient variability. The pre-dose trough concentration (C-min) is commonly used for therapeutic drug monitoring. With the new microemulsion (Neoral), intrapatient variability was reduced. However, the usefulness of Neoral C-min was questioned. Firstly, because of the improved and more-rapid absorption, accidental intake before blood sampling has a greater impact on C-min than with classic cyclosporine. Secondly, C-min may be low despite high drug exposure, due to rapid clearance in children. A full pharmacokinetic (PK) profile with determination of the area under the curve (AUC) is expensive and cumbersome, and therefore a search for an abbreviated AUC began. Here, we present a retrospective analysis of 84 PK profiles from 78 pediatric renal transplant. recipients. By analysis of rejection episodes and toxicity, we estimated a target AUC above 5,000 ngxh/ml in the early post-transplant period and 3,900 ngxh/ml beyond 100 days. The abbreviated AUC using the 2- and 6-h concentrations (C2 and C6) and a simple estimate derived from the 3-h concentration (C3) were equally well correlated with the AUG. From our data, we recommend a target C3 at approximately 800 ng/ml early after transplantation and 450-550 ng/ml beyond 100 days.