Objective: Saliva is purported to have a close correspondence to plasma concentrations due to a passive diffusion process from plasma to saliva. However, limited data are available characterizing oxycodone and its metabolites in saliva. The purpose of this analysis was to evaluate the use of saliva monitoring in patients prescribed oxycodone and to compare the disposition of oxycodone in saliva and urine.
Design: This retrospective analysis examined deidentified urine and saliva specimens collected from patients with chronic pain. These specimens were received at Millennium Laboratories between March and June 2012 and analyzed using LCMS/MS to quantitate oxycodone, noroxycodone, and oxymorphone concentrations.
Results: The geometric mean metabolic ratio (MR) of noroxycodone to oxycodone in saliva was 0.11, whereas the geometric mean MR in urine was 1.7. The geometric mean oxycodone concentration in saliva was 860 ng/mL (range, 1.5-8,600,000 ng/mL; 95% CI, 770-950 ng/mL), whereas the geometric mean noroxycodone concentration was 98 ng/mL (range, 2.3-8,800 ng/mL; 95% CI, 90-107 ng/mL). Fifty-four of the saliva specimens (6 percent) had oxycodone concentrations between 10,000 and 9,000,000 ng/mL.
Conclusions: Oxycodone is predominant over noroxycodone in saliva (similar to plasma), while the reverse relationship exists in urine. Much greater oxycodone concentrations were found in saliva than are expected in plasma (up to a 1,000-fold difference). Saliva concentrations are lower than urine concentrations but still may not reflect plasma disposition. Possible explanations include medication residue in the mouth (recent medication use or misuse) or active secretion into saliva. Saliva analysis may be used for qualitative drug monitoring of oxycodone, with detection rates similar to urine; however, further characterization is needed for appropriate interpretation.