WHOLE-BLOOD CYCLOSPORINE-G IN RENAL-TRANSPLANT RECIPIENTS DETERMINED BY 2 IMMUNOASSAYS AND LIQUID-CHROMATOGRAPHY

Cyclosporin G (CsG) is less nephrotoxic than cyclosporin A (CsA) and i s undergoing clinical trials for use as an immunosuppressive agent aft er renal transplantation. Three assays for whole-blood CsA-HPLC, RIA ( INCSTAR, Cyclo-Trac SP), and FPIA (Abbott TD(x))-were were adapted for use with CsG and were assessed for analytical suitability and to dete rmine which assay was capable of deriving CsG values rapidly after tra nsplantation. The assays were acceptable in terms of sensitivity, line arity, analytical recovery, and precision. When considering blood samp les (n = 107) from renal transplant recipients receiving a low dose of CsG (5 mg/kg per day) and a high dose (10 mg/kg per day), we obtained the following correlation data: RIA = 0.974HPLC + 27.89 (r = 0.9798, S(y\x) = 39.24); FPIA = 0.964HPLC + 33.59 (r = 0.9819, S(y\x) = 36.66) ; and FPIA = 0.977RIA + 9.50 (r = 0.9894, S(y\x) = 28.12). The FPIA of CsG is recommended as the most rapid method, although it is the most expensive. HPLC, RIA, and FPIA were capable of accurately deriving pro jected CsG concentrations at various stages of the clinical trial when the low- and high-dose regimes were tapered over a period of 16 weeks .