Disposition of opioids in oral fluid: Importance of chromatography and mass spectral transitions in LC‐MS/MS

Abstract

The use of prescription pain relievers, specifically opioids, has been increasing over the last few years. Oral fluid is easier to collect than urine, is difficult to adulterate, and is a reflection of free drug in the body, so its analysis is becoming more widespread in the monitoring of opioids. The demethylated metabolites of oxycodone, hydrocodone, and codeine are present at higher concentrations in oral fluid than oxymorphone, hydromorphone, and morphine, respectively; therefore, their detection in saliva indicates ingestion of the medication rather than diversion, and should be included in the analysis of opioids in this matrix. Since the compounds have the same nominal molecular weights, the same M + H(+) precursor ions in positive electrospray mode, and potentially identical collisionally activated fragmentation patterns, the importance of chromatography to separate the various opioids as well as the selection of mass spectral transitions is critical for correct identification. A procedure for the simultaneous determination of 12 opioid related compounds in oral fluid using liquid chromatography with tandem mass spectrometry (LC-MS/MS) is presented. The recovery of opioids from the collection device was over 80% at 20 ng/ml; intra-day imprecision was less than 6.8%; inter-day imprecision less than 6.2%. In authentic specimens, the predominant metabolite of oxycodone was noroxycodone; for specimens containing codeine, no morphine was detected; and for hydrocodone positives, norhydrocodone was detected at significantly higher levels than hydromorphone. The importance of monitoring specific mass spectral transitions and chromatographic separation is demonstrated.