Assessment of the Utility of the Oral Fluid and Plasma Proteomes for Hydrocodone Exposure

Abstract

Introduction: Non-medical use and abuse of prescription opioids is a growing problem in both the civilian and military communities, with minimal technologies for detecting hydrocodone use. This study explored the proteomic changes that occur in the oral fluid and blood plasma following controlled hydrocodone administration in 20 subjects.

Methods: The global proteomic profile was determined for samples taken at four time points per subject: pre-exposure and 4, 6, or 168 hours post-exposure. The oral fluid samples analyzed herein provided greater differentiation between baseline and response time points than was observed with blood plasma, at least partially due to significant person-to-person relative variability in the plasma proteome.

Results: A total of 399 proteins were identified from oral fluid samples, and the abundance of 118 of those proteins was determined to be significantly different upon metabolism of hydrocodone (4 and 6 hour time points) as compared to baseline levels in the oral fluid (pre-dose and 168 hours).

Conclusions: We present an assessment of the oral fluid and plasma proteome following hydrocodone administration, which demonstrates the potential of oral fluid as a noninvasive sample that may reveal features of hydrocodone in opioid use, and with additional study, may be useful for other opioids and in settings of misuse.

Keywords: Hydrocodone; Opioid; Oral fluid; Plasma; Proteomics.

Fig. 1

Metabolite profile of hydrocodone, hydromorphone, and norhydrocodone in plasma. Concentration of a hydrocodone, b hydromorphone, and c norhydrocodone in blood plasma was measured by LC-MS/MS at multiple time points (zero to 168 hours post-administration) in 11 subjects. Data are plotted in line graph form through time. Legend in a applies to all a through c graphs.

Fig. 2

A subset of proteins in oral fluid exhibit altered abundance following hydrocodone administration. The 118 proteins identified in oral fluid to be significantly altered in relative abundance following hydrocodone administration are represented here. These proteins were determined by a linear mixed effects model, comparing the baseline (pre-dose and 168 h time points) to the response (4 and 6 hours time points) proteome. Values represented are protein abundance measures that have been Z-score scaled across all time points to highlight increased or decreased abundance in baseline vs. response. Red shading indicates higher protein abundance and green indicates lower protein abundance levels.