title: Measurement of warfarin in the oral fluid of patients undergoing anticoagulant oral therapy.
abstract: BACKGROUND
  Patients on warfarin therapy undergo invasive and expensive checks for the coagulability of their blood. No information on coagulation levels is currently available between two controls.
  
  
  METHODS
  A method was developed to determine warfarin in oral fluid by HPLC and fluorimetric detection. The chromatographic separation was performed at room temperature on a C-18 reversed-phase column, 65% PBS and 35% methanol mobile phase, flow rate 0.7 mL/min, injection volume 25 µL, excitation wavelength 310 nm, emission wavelength 400 nm.
  
  
  RESULTS
  The method was free from interference and matrix effect, linear in the range 0.2-100 ng/mL, with a detection limit of 0.2 ng/mL. Its coefficient of variation was <3% for intra-day measurements and <5% for inter-day measurements. The average concentration of warfarin in the oral fluid of 50 patients was 2.5±1.6 ng/mL (range 0.8-7.6 ng/mL). Dosage was not correlated to INR (r = -0.03, p = 0.85) but positively correlated to warfarin concentration in the oral fluid (r = 0.39, p = 0.006). The correlation between warfarin concentration and pH in the oral fluid (r = 0.37, p = 0.009) confirmed the importance of pH in regulating the drug transfer from blood. A correlation between warfarin concentration in the oral fluid and INR was only found in samples with pH values ≥7.2 (r = 0.84, p = 0.004).
  
  
  CONCLUSIONS
  Warfarin diffuses from blood to oral fluid. The method allows to measure its concentration in this matrix and to analyze correlations with INR and other parameters.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale-Università di Pisa, Pisa, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Ghimenti
authors.forename: Tommaso
authors.initials: T
authors.lastname: Lomonaco
authors.forename: Massimo
authors.initials: M
authors.lastname: Onor
authors.forename: Laura
authors.initials: L
authors.lastname: Murgia
authors.forename: Aldo
authors.initials: A
authors.lastname: Paolicchi
authors.forename: Roger
authors.initials: R
authors.lastname: Fuoco
authors.forename: Lucia
authors.initials: L
authors.lastname: Ruocco
authors.forename: Giovanni
authors.initials: G
authors.lastname: Pellegrini
authors.forename: Maria Giovanna
authors.initials: MG
authors.lastname: Trivella
authors.forename: Fabio
authors.initials: F
authors.lastname: Di Francesco
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000032:analysis / Q000627:therapeutic use*; D001777:Blood Coagulation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D016903:Drug Monitoring / Q000379:methods; D005260:Female; D005470:Fluorometry / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D025341:Principal Component Analysis; D015203:Reproducibility of Results; D012463:Saliva / Q000187:drug effects* / Q000378:metabolism; D014859:Warfarin / Q000032:analysis / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014859:Warfarin