Liquid chromatographic determination of cyclosporin A in serum with use of a solid-phase extraction. Comparison between high-performance liquid chromatography and radioimmunoassay levels in clinical investigations.

A simple reliable liquid chromatographic method for assay of cyclosporin A in serum or urine is described. Samples were cleaned up on a solid-phase extraction system (cyanopropyl column). The system involved a reversed-phase C18 Ultrasphere column maintained at 72 degrees C and an acetonitrile linear gradient (65 to 95%) in 0.14% triethylammonium phosphate. Liquid chromatographic analysis of radioimmunoassay standards shows that some samples contain a contaminant peak. Comparison of cyclosporin A levels obtained by radioimmunoassay and high-performance liquid chromatography in clinical investigations show that the former values are generally, but not always, higher than the latter, and that cyclosporin A is very differently metabolized depending on the patient, disease and treatment.