title: Opioid Concentrations in Oral Fluid and Plasma in Cancer Patients With Pain.
abstract: BACKGROUND
  Measuring opioid concentrations in pain treatment is warranted in situations where optimal opioid analgesia is difficult to reach.
  
  
  OBJECTIVE
  To assess the usefulness of oral fluid (OFL) as an alternative to plasma in opioid concentration monitoring in cancer patients on chronic opioid therapy.
  
  
  METHODS
  We collected OFL and plasma samples from 64 cancer patients on controlled-release (CR) oral morphine, CR oral oxycodone, or transdermal (TD) fentanyl for pain. Samples were obtained on up to five separate days.
  
  
  RESULTS
  A total of 213 OFL and plasma samples were evaluable. All patients had detectable amounts of the CR or TD opioid in both plasma and OFL samples. The plasma concentrations of oxycodone and fentanyl (determination coefficient R(2) = 0.628 and 0.700, respectively), but not morphine (R(2) = 0.292), were moderately well correlated to the daily opioid doses. In contrast to morphine and fentanyl (mean OFL/plasma ratio 2.0 and 3.0, respectively), the OFL oxycodone concentrations were significantly higher than the respective plasma concentrations (mean OFL/plasma ratio 14.9). An active transporter could explain the much higher OFL vs. plasma concentrations of oxycodone compared with morphine and fentanyl.
  
  
  CONCLUSIONS
  OFL analysis is well suited for detecting the studied opioids. For morphine and fentanyl, an approximation of the plasma opioid concentrations is obtainable, whereas for oxycodone, the OFL/plasma concentration relationship is too variable for reliable approximation results.
authors.affiliation: Pain Clinic, Department of Anesthesiology and Intensive Care Medicine, Helsinki University Central Hospital, Helsinki, Finland. Electronic address: tarja.heiskanen@hus.fi.
authors.forename: Tarja
authors.initials: T
authors.lastname: Heiskanen
authors.affiliation: Alcohol and Drug Analytics Unit, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Kaarina
authors.initials: K
authors.lastname: Langel
authors.affiliation: Alcohol and Drug Analytics Unit, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Teemu
authors.initials: T
authors.lastname: Gunnar
authors.affiliation: Injury Prevention Unit, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Pirjo
authors.initials: P
authors.lastname: Lillsunde
authors.affiliation: Pain Clinic, Department of Anesthesiology and Intensive Care Medicine, Helsinki University Central Hospital, Helsinki, Finland; Institute of Clinical Medicine, University of Helsinki, Helsinki, Finland.
authors.forename: Eija A
authors.initials: EA
authors.lastname: Kalso
mesh_terms: D000279:Administration, Cutaneous; D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D001774:Blood Chemical Analysis; D003692:Delayed-Action Preparations; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D005283:Fentanyl / Q000493:pharmacokinetics / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000493:pharmacokinetics / Q000627:therapeutic use; D009055:Mouth; D009369:Neoplasms / Q000188:drug therapy / Q000503:physiopathology*; D010098:Oxycodone / Q000493:pharmacokinetics / Q000627:therapeutic use; D010146:Pain / Q000188:drug therapy* / Q000503:physiopathology*
chemical_list: D000701:Analgesics, Opioid; D003692:Delayed-Action Preparations; D009020:Morphine; D010098:Oxycodone; D005283:Fentanyl
keywords: Opioid; concentration; oral fluid; plasma