title: Evaluation of essential parameters in the chromatographic determination of cyclosporin A and metabolites using a D-optimal design.
abstract: The extensive use of routine monitoring of cyclosporin A (INN, ciclosporin) whole blood levels of patients undergoing such therapy has resulted in a wide variety of chromatographic conditions for analysing this drug. The aim of this study was to evaluate the importance of essential parameters in the chromatographic determination of cyclosporin A and its main metabolites, AM1, AM9 and AM4N. A D-optimal design was used to evaluate the effect of type and amount of organic modifier, temperature, flow rate, pH and gradient steepness. The optimal chromatographic conditions were determined by multi-linear regression. In the final chromatographic method separation of the compounds was carried out on a reversed phase C(8) column maintained at 80 degrees C. The mobile phase consisted of a linear gradient with two mobile phases containing acetonitrile and water. The flow rate was set at 0.8 ml/min. UV detection was carried out at 214 nm. Validation of the analytical method showed linearity over the range 25-1000 ng/ml (r>0.997). The detection limits of cyclosporin A, AM1, AM9 and AM4N were 1.3 pmol on column. The within-day and between-day relative standard deviations were <15% for cyclosporin A at all concentrations and for the metabolites at 250 and 1000 ng/ml, and <21% for the metabolites at limit of quantification (25 ng/ml).
authors.affiliation: Department of Pharmacology, School of Pharmacy, University of Oslo, Blindern, N-0316, Oslo, Norway. monicahe@farmasi.uio.no
authors.forename: M
authors.initials: M
authors.lastname: Hermann
authors.forename: H
authors.initials: H
authors.lastname: Christensen
authors.forename: J L E
authors.initials: JL
authors.lastname: Reubsaet
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D016572:Cyclosporine / Q000032:analysis* / Q000097:blood / Q000737:chemistry / Q000378:metabolism*
chemical_list: D016572:Cyclosporine