title: Simultaneous LC-MS/MS quantification of P-glycoprotein and cytochrome P450 probe substrates and their metabolites in DBS and plasma.
abstract: BACKGROUND
  An LC-MS/MS method has been developed for the simultaneous quantification of P-glycoprotein (P-gp) and cytochrome P450 (CYP) probe substrates and their Phase I metabolites in DBS and plasma. P-gp (fexofenadine) and CYP-specific substrates (caffeine for CYP1A2, bupropion for CYP2B6, flurbiprofen for CYP2C9, omeprazole for CYP2C19, dextromethorphan for CYP2D6 and midazolam for CYP3A4) and their metabolites were extracted from DBS (10 µl) using methanol. Analytes were separated on a reversed-phase LC column followed by SRM detection within a 6 min run time.
  
  
  RESULTS
  The method was fully validated over the expected clinical concentration range for all substances tested, in both DBS and plasma. The method has been successfully applied to a PK study where healthy male volunteers received a low dose cocktail of the here described P-gp and CYP probes. Good correlation was observed between capillary DBS and venous plasma drug concentrations.
  
  
  CONCLUSIONS
  Due to its low-invasiveness, simple sample collection and minimal sample preparation, DBS represents a suitable method to simultaneously monitor in vivo activities of P-gp and CYP.
authors.affiliation: Division of Clinical Pharmacology & Toxicology, Geneva University Hospitals, Rue Gabrielle Perret-Gentil 4, 1211, Geneva, Switzerland.
authors.forename: Marija
authors.initials: M
authors.lastname: Bosilkovska
authors.forename: Julien
authors.initials: J
authors.lastname: Déglon
authors.forename: Caroline
authors.initials: C
authors.lastname: Samer
authors.forename: Bernhard
authors.initials: B
authors.lastname: Walder
authors.forename: Jules
authors.initials: J
authors.lastname: Desmeules
authors.forename: Christian
authors.initials: C
authors.lastname: Staub
authors.forename: Youssef
authors.initials: Y
authors.lastname: Daali
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D016642:Bupropion / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D002110:Caffeine / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000592:standards; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003915:Dextromethorphan / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D059788:Dried Blood Spot Testing; D005480:Flurbiprofen / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D006207:Half-Life; D008297:Male; D008874:Midazolam / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D009853:Omeprazole / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D004364:Pharmaceutical Preparations / Q000097:blood* / Q000378:metabolism; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry / Q000592:standards; D016593:Terfenadine / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004364:Pharmaceutical Preparations; D016642:Bupropion; D002110:Caffeine; D005480:Flurbiprofen; D003915:Dextromethorphan; D016593:Terfenadine; D003577:Cytochrome P-450 Enzyme System; C093230:fexofenadine; D009853:Omeprazole; D008874:Midazolam