title: Development and validation of a new method to simultaneously quantify triazoles in plasma spotted on dry sample spot devices and analysed by HPLC-MS.
abstract: OBJECTIVE
  Therapeutic drug monitoring (TDM) of triazoles is widely used in clinical practice to optimize therapy. TDM is limited by technical problems and cost considerations, such as sample storage and dry-ice shipping. We aimed to develop and validate a new method to analyse itraconazole, posaconazole and voriconazole in plasma spotted on dry sample spot devices (DSSDs) and to quantify them by an HPLC system.
  
  
  METHODS
  Extraction from DSSDs was done using n-hexane/ethyl acetate and ammonia solution. Samples were analysed using HPLC with mass spectrometry (HPLC-MS). Accuracy and precision were assayed by inter- and intra-day validation. The stability of triazoles in plasma spotted on DSSDs was investigated at room temperature for 1 month. The method was compared with a validated standard HPLC method for quantification of triazoles in human plasma.
  
  
  RESULTS
  Mean inter- and intra-day accuracy and precision were <15% for all compounds. Triazoles were stable for 2 weeks at room temperature. The method was linear (r(2) > 0.999) in the range 0.031-8 mg/L for itraconazole and posaconazole, and 0.058-15 mg/L for voriconazole. High sensitivity was observed; limits of detection were 0.008, 0.004 and 0.007 mg/L for itraconazole, posaconazole and voriconazole, respectively. A high degree of correlation (r(2) > 0.94) was obtained between the DSSD method and the standard method of analysis.
  
  
  CONCLUSIONS
  The method that we developed and validated to quantify triazoles in human plasma spotted on DSSDs is accurate and precise. It overcomes problems related to plasma sample storage and shipment, allowing TDM to be performed in a cheaper and safer manner.
authors.affiliation: Laboratory of Clinical Pharmacology and Pharmacogenetics, Department of Infectious Diseases, University of Turin, Amedeo di Savoia Hospital, Corso Svizzera 164, 10149 Turin, Italy. lorena.baietto@unito.it
authors.forename: Lorena
authors.initials: L
authors.lastname: Baietto
authors.forename: Antonio
authors.initials: A
authors.lastname: D'Avolio
authors.forename: Cristina
authors.initials: C
authors.lastname: Marra
authors.forename: Marco
authors.initials: M
authors.lastname: Simiele
authors.forename: Jessica
authors.initials: J
authors.lastname: Cusato
authors.forename: Simone
authors.initials: S
authors.lastname: Pace
authors.forename: Alessandra
authors.initials: A
authors.lastname: Ariaudo
authors.forename: Francesco Giuseppe
authors.initials: FG
authors.lastname: De Rosa
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Perri
mesh_terms: D000935:Antifungal Agents / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003890:Desiccation; D016903:Drug Monitoring / Q000379:methods*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D010949:Plasma / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods; D014230:Triazoles / Q000032:analysis*
chemical_list: D000935:Antifungal Agents; D014230:Triazoles