title: Micromethod for quantification of cinacalcet in human plasma by liquid chromatography-tandem mass spectrometry using a stable isotope-labeled internal standard.
abstract: BACKGROUND
  Cinacalcet hydrochloride is a calcimimetic agent indicated for the treatment of secondary hyperparathyroidism in dialysis-dependent patients with chronic kidney disease. In the context of a pharmacokinetic (PK)/pharmacodynamic study of cinacalcet in dialysis-dependent chronic kidney disease children with secondary hyperparathyroidism, we describe the development and validation of a new, rapid, simple, and economical liquid chromatography-tandem mass spectrometry (LC-MS/MS) micromethod for quantifying cinacalcet plasma concentrations.
  
  
  METHODS
  Cinacalcet was analyzed in 50-μL plasma samples over a wide range of concentrations (0.1-100 ng/mL) by LC-MS/MS after protein precipitation and addition of deuterated cinacalcet as the internal standard. Cinacalcet was quantified using selective reaction monitoring of the specific transition m/z 358.1 > 155.1, with the 361.1 > 158.1 transition used for the internal standard. The suitability of the assay for clinical PK studies was evaluated using data from a pilot PK study in a pediatric patient.
  
  
  RESULTS
  The overall turnaround time for the assay was 20 minutes. The lower limit of quantification of the method was 0.1 ng/mL. Intraassay imprecision and inaccuracy for quality control samples ranged from 2.8% to 9% and 100% to 102%, respectively. Interassay imprecision and inaccuracy ranged from 6.9% to 8.5% and 99% to 103%, respectively. The overall recovery ranged from 90% to 106%. No ion suppression due to matrix effects was found with different preanalytical conditions, such as hemolysis, lipemia, and hyperuricemia.
  
  
  CONCLUSIONS
  This LC-MS/MS micromethod provides high specificity, precision, and accuracy for rapid quantification of cinacalcet plasma concentrations, and it is suitable for application in pediatric PK studies; it also has potential for use in the establishment of target ranges and ultimately routine therapeutic drug monitoring to optimize cinacalcet dosing.
authors.affiliation: Clinical Pathology Laboratory Unit, IRCCS Giannina Gaslini Institute, Genoa, Italy. giulianacangemi@ospedale-gaslini.ge.it
authors.forename: Giuliana
authors.initials: G
authors.lastname: Cangemi
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Barco
authors.forename: Enrico E
authors.initials: EE
authors.lastname: Verrina
authors.forename: Samuele
authors.initials: S
authors.lastname: Scurati
authors.forename: Giovanni
authors.initials: G
authors.lastname: Melioli
authors.forename: Ornella
authors.initials: O
authors.lastname: Della Casa Alberighi
mesh_terms: D000328:Adult; D057966:Calcimimetic Agents / Q000097:blood*; D002648:Child; D002853:Chromatography, Liquid / Q000379:methods*; D000069449:Cinacalcet; D002986:Clinical Trials as Topic; D016903:Drug Monitoring / Q000379:methods*; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood / Q000188:drug therapy; D007553:Isotope Labeling; D008832:Microchemistry / Q000379:methods; D009281:Naphthalenes / Q000097:blood* / Q000627:therapeutic use; D010865:Pilot Projects; D011786:Quality Control; D012015:Reference Standards; D006435:Renal Dialysis / Q000379:methods; D051436:Renal Insufficiency, Chronic / Q000097:blood; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D057966:Calcimimetic Agents; D009281:Naphthalenes; D000069449:Cinacalcet