Effective use of liquid chromatography-mass spectrometry (LC/MS) in the routine clinical laboratory for monitoring sirolimus, tacrolimus, and cyclosporine.

The authors describe an isocratic liquid chromatographic/electrospray single quadrupole mass spectrometric assay suitable for routine therapeutic monitoring of the antirejection drugs tacrolimus, sirolimus, and cyclosporine in blood. The drugs and added internal standards, ascomycin, desmethoxysirolimus, and cyclosporine G, are extracted from a protein-free supernatant of patient blood on a Strata SDB-L styrene-divinylbenzene polymeric extraction cartridge (Phenomenex, Torrance, CA). A Gilson Aspec XL-4 (Gilson Instruments, Middleton, WI) is programmed to perform the extraction and transfer the extract to autosampler vials.