Quantitative determination of cyclosporin A in whole blood and plasma by high performance liquid chromatography

A simple, specific and sensitive method for monitoring therapeutic levels of the immunosuppressive agent cyclosporin A (CyA) in whole blood and plasma has been developed which uses a high performance liquid chromatography and involves a simple liquid-liquid extraction procedure. Samples were delipolysed with 0.1 mM dextran sulfate sodium salt, extracted with n-hexane, and chromatographed on a Lichrosorb Si-60 column with UV detection at 215 nm. Each of CyA and internal standard (cyclosporin D) is resoluted clearly as a single peak and no interfering peaks are observed on the chromatograms. The detection limit is 5 ng/ml in whole blood and plasma. The reproducibility assessed by repeated analysis is satisfactory, that is to say, each coefficient of variation of the within-run and between-run precision is below 4%. The analytical recovery of added CyA is almost complete. This method is sensitive enough for monitoring whole blood and plasma levels of CyA in renal transplant patients in the therapeutic dose range, and is also applicable to the study on the distribution of CyA between plasma and non-plasma fractions of blood in patients with renal allografts.