Pharmacokinetics of two cyclosporine formulations using FPIA and HPLC assay in volunteers

Abstract

The analytical methods for the analysis of cycloporine (CsA), a fluorescence polarization immunoassay (FPIA) and HPLC method, were compared in a pharmacokinetic study of two CsA soft capsule formulations (Sandimmun®; Sandoz, Implanta®; Hanmi). Sixteen healthy volunteers completed the study and each subject ingested single doses (4×100 mg) of the test and the reference formulations in a two-way crossover design with a one-week drug-free interval between doses. Following each administration, whole blood concentrations of CsA were monitored over a period of 24 hour by both FPIA and HPLC methods. Blood concentrations and pharmacokinetic parameters determined by either analytical method showed large intersubject variation, with the FPIA data showing relatively higher magnitude of intersubject variation than the HPLC data. The blood concentrations determined by FPIA were 1.1–1.3 times higher than those determined by HPLC. There were strong and significant correlations between the two methods (r>0.83: p 0.05. tmax was earlier and Cmax was slightly lower for the test formulation. AUC24h, Cmax, tmax and MRT determined separately from the data obtained by the two methods for the two formulations were examined by analyses of variance (ANOVA) for the bioequivalency evaluation. Results of ANOVA and confidence limits of test/reference ratios of AUC24h, Cmax, tmax and MRT, and statistical tests indicated the bioequivalence of the two formulations (i.e., test/reference ratio was within 100×20%) except for Cmax and tmax. The mean of Cmax showed only 7.9% and 11.6% differences but the detection limit were 26.6% and 21.4% as determined by FPIA and HPLC respectively which is slightly over the 20% criteria. The mean of tmax also showed 11.1% and 9.3% differences but the detection limit were 29.2% and 29.6% as determined by FPIA and HPLC respectively. This experiments suggest that the data yielded for the two formulations demonstrated that they were bioequivalent.