title: A HPLC-mass spectrometric method suitable for the therapeutic drug monitoring of everolimus.
abstract: We report here the validation of an HPLC-electrospray-tandem mass spectrometry method for the quantification of everolimus, an immunosuppressant drug. Whole blood samples (100 microl) were extracted by protein precipitation which involved sample pre-treatment with zinc sulphate followed by acetonitrile (containing internal standard, 40-O-(3'-hydroxy)propyl-rapamycin). HPLC was performed using a step-gradient at a flow rate of 0.6 ml/min on a Waters TDM C18 column (10 mm x 2.1mm I.D.) with a resultant chromatographic analysis time of 2 min. Mass spectrometric detection by selected reaction monitoring (everolimus m/z 975.5-->908.3; internal standard m/z 989.5-->922.3). The assay was linear from 0.5 to 40 microg/l (r2>0.994, n=11). The inter- and intra-day analytical recovery and imprecision for quality control samples (1.25, 12.5 and 30 microg/l) were 93.4-98.2% and <10.7%, respectively (n=10). At the lower limit of quantification (0.5 microg/l) the inter- and intra-day analytical recovery was 94.4-95.8% with imprecision of <14.1% (n=10). The absolute recovery of everolimus (6.5 microg/l) and internal standard (12.5 microg/l) was 96.5 and 88.3%, respectively (n=3). A comparison of our method against the mean of all HPLC methods for a series of samples from an external proficiency testing scheme revealed good correlation as shown by the regression analysis: y=0.973x+0.301 (r2=0.986, n=71). In conclusion, the method described is suited to the current requirements for therapeutic drug monitoring of everolimus.
authors.affiliation: Department of Medicine, University of Queensland, Brisbane, Qld. 4102, Australia. ptaylor@soms.uq.edu.au
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Taylor
authors.forename: Michael E
authors.initials: ME
authors.lastname: Franklin
authors.forename: Kendon S
authors.initials: KS
authors.lastname: Graham
authors.forename: Peter I
authors.initials: PI
authors.lastname: Pillans
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D016903:Drug Monitoring / Q000379:methods; D000068338:Everolimus; D006801:Humans; D015394:Molecular Structure; D015203:Reproducibility of Results; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000068338:Everolimus; D020123:Sirolimus