EQUIVALENCE OF CYCLOSPORINE BLOOD LEVEL ASSAYS IN PATIENTS RECEIVING CYCLOSPORINE MICROEMULSION OR CYCLOSPORINE

The more rapid absorption of the cyclosporin A (CyA) microemulsion for mulation (Neoral, NEO) compared to Sandimmune (SIM) might bypass intes tinal metabolism resulting in differing amounts of CyA metabolites in blood as compared to SLM. If true, then CyA levels obtained with a CyA monoclonal antibody assay (TDx) that has metabolite cross-reactivity might differ depending on the CyA formulation received by the patient, thereby affecting safety and efficacy. Fifty-one NEO vs. 50 SIM treat ed de novo renal transplant recipients from a multicenter double-blind randomized trial had morning, whole-blood, trough-samples obtained at the ends of weeks 1, 4, 8, and 12 post-transplant assayed for CYA by HPLC and TDx. The slopes (ratio of TDx value to HPLC value) for the re gression lines between TDx and HPLC levels as a function of time post- transplant and CyA formulation were determined using a general linear model. For NEO, the slopes at each week(1.21-1.41 x HPLC) did not diff er significantly (p=0.82). For SLM, the week 1 slope (1.2) was signifi cantly (p=0.006) less than the other weeks (1.4-1.44). The slopes (NEO vs. SIM) were not different at either week 1 (1.21 vs. 1.22, p=0.82) or at pooled weeks 4, 8, and 12 (1.33 vs. 1.4, p=0.1). These results i ndicate that despite the improved absorption, TDx values obtained on N EO are qualitatively similar to those obtained on SIM.