title: Simultaneous quantification of cyclosporine, tacrolimus, sirolimus and everolimus in whole blood by liquid chromatography-electrospray mass spectrometry.
abstract: OBJECTIVE
  The aim of this work was to develop a selective method for the simultaneous quantification of cyclosporine, tacrolimus, sirolimus and everolimus in whole blood.
  
  
  METHODS
  An automated on-line solid-phase extraction system coupled with liquid chromatography-mass spectrometry (LC-MS) was used. After a simple protein precipitation, the supernatant was load on a C8 column with a mobile phase composed of MeOH/H(2)O (5/95 v/v), supplemented with formic acid 0.02% and sodium formate 1 muM. After column-switching, the analytes were transferred in the back-flush mode on a C18 column with MeOH/H(2)O (65/35). The valve was then commuted to its initial position and the chromatographic separation was performed with a gradient of MeOH/H(2)O (65/35-95/5). The sodium adducts [M+Na](+) were monitored for quantification with an electrospray ionization-single quadrupole MS.
  
  
  RESULTS
  The LC-MS assay was fully validated on a concentration range of 2.5-30 ng/mL for tacrolimus, sirolimus and everolimus and of 50-1500 ng/mL for cyclosporine, allowing a quantification of cyclosporine 2 h post-dose without sample dilution. Trueness, repeatability and intermediate precision were found to be satisfactory.
  
  
  CONCLUSIONS
  This method provided a selective, rapid and automated procedure that can be easily used for routine quantification of immunosuppressive drugs in most clinical laboratories.
authors: Laboratory Medicine Service, University Hospitals of Geneva, Geneva, Switzerland.
authors: Nicolas
authors: N
authors: Ansermot
authors: Marc
authors: M
authors: Fathi
authors: Jean-Luc
authors: JL
authors: Veuthey
authors: Jules
authors: J
authors: Desmeules
authors: Serge
authors: S
authors: Rudaz
authors: Denis
authors: D
authors: Hochstrasser
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods / Q000592:standards; D016572:Cyclosporine / Q000097:blood* / Q000737:chemistry; D000068338:Everolimus; D006801:Humans; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000097:blood* / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods / Q000592:standards; D016559:Tacrolimus / Q000097:blood* / Q000737:chemistry
chemical_list: D016572:Cyclosporine; D000068338:Everolimus; D020123:Sirolimus; D016559:Tacrolimus