title: Measurement of sirolimus in whole blood using high-performance liquid chromatography with ultraviolet detection.
abstract: BACKGROUND
  Sirolimus, a potent immunosuppressive drug, exhibits intrapatient and interpatient variability of absorption and metabolism. Thus, therapeutic drug monitoring is important.
  
  
  OBJECTIVE
  This paper describes a reverse-phase high-performance liquid chromatography (HPLC) method, using ultraviolet (UV) absorption for detection, for measuring sirolimus levels in human whole-blood samples.
  
  
  METHODS
  The stability of sirolimus in whole blood was assessed under conditions likely to be encountered during transport of study samples to a central laboratory. The performance of the HPLC-UV assay in measuring sirolimus was compared with that of 3 established, validated HPLC assays with tandem mass-spectrometric (MS/MS) detection. Results of the HPLC-UV assay also were compared with results produced by a prototype microparticle enzyme immunoassay (MEIA).
  
  
  RESULTS
  Inaccuracy for 3 in-house control samples was < or =4%, whereas within-assay repeatability (coefficient of variation [CV]) was < or =5% and between-assay reproducibility was < or =6.6%. Mean recovery of sirolimus from blood was 81.5%+/-4.3%. The lower limit of quantification was set at 6.5 ng/mL, and the repeatability CV at this concentration was 4.2% (n = 6). Sirolimus-containing whole-blood samples were stable for 3 freeze/thaw cycles when stored at -20 degrees C and for > or =2 days when stored at ambient temperature. The sample extract was shown to be stable for up to 54 hours at ambient temperature (approximately 22 degrees C) after extraction. Results of the HPLC-UV assay were consistent with those of the HPLC/ MS/MS assays but lower than those produced by MEIA.
  
  
  CONCLUSIONS
  This HPLC-UV method is considered suitable for therapeutic drug monitoring of sirolimus.
authors.affiliation: Analytical Unit, St. George's Hospital Medical School, London, England.
authors.forename: D W
authors.initials: DW
authors.lastname: Holt
authors.forename: T
authors.initials: T
authors.lastname: Lee
authors.forename: A
authors.initials: A
authors.lastname: Johnston
mesh_terms: D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D005615:Freezing; D006801:Humans; D007166:Immunosuppressive Agents / Q000097:blood*; D012015:Reference Standards; D015203:Reproducibility of Results; D020123:Sirolimus / Q000097:blood*; D013048:Specimen Handling; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
chemical_list: D007166:Immunosuppressive Agents; D020123:Sirolimus