Ciclosporin monitoring in kidney-transplanted children: high-performance liquid chromatography versus radioimmunoassay.

Due to large individual differences in absorption, utilization and metabolism of the predominantly used drug ciclosporin (CsA) for selective immunosuppression in kidney graft recipients, therapeutic blood levels (immunosuppression/toxicity) can be maintained only by frequent measurements of the CsA concentrations in blood samples and dosage readjustments. The purpose of the present study was to investigate the usefulness of a high-performance liquid chromatography (HPLC) method for native CsA and a radioimmunoassay (RIA) method for CsA and metabolites measuring simultaneously using both HPLC and RIA and creatinine serum levels (Crea) in whole blood samples from 19 kidney-transplanted children over a 3-year observation period. By comparison of the results of HPLC, RIA and Crea determinations (n = 1,284) we found a highly variable metabolization rate (RIA/HPLC ratio) of 5.25 +/- 2.33 (range 1.37-12.9). No direct correlation was found between changes in RIA/HPLC ratios and kidney function, rejection and infection periods. Dosage/HPLC and dosage/RIA showed no significant correlation. A higher correlation between HPLC, Crea and nephrotoxicity was found than between RIA and Crea. Because of rapid and large variations of CsA metabolization rates in young allograft recipients, we recommend measurements of CsA blood concentrations with any HPLC method specific for unchanged drug, since CsA metabolites detected by RIA, at least those which are most abundant, have less immunosuppressive and toxic effects.