• Davis, Lisa
• Hayes, Eugene D.
• Flegel, Ronald

Abstract

Background and aim: In workplace drug testing, total morphine is an important urinary marker of opioid use, but low morphine levels (&lt;4,000 ng/mL) are difficult to interpret as morphine can be present from heroin use, prescription codeine and morphine use as well as poppy seed ingestion. In morphine positive specimens, 6-acetylmorphine has traditionally been an important marker to identify heroin use. However, in the third wave of the US opioid epidemic, fentanyl is replacing heroin in the drug supply and is a common contaminant in heroin and other street drugs. The aim of this study was to evaluate whether fentanyl is now a better marker of heroin use in morphine positive urine specimens than 6-acetylmorphine, given the changing drug market.<br/>Methods: The concentrations of opioids (morphine, 6-acetylmorphine, fentanyl and metabolites, semi-synthetic opioids, and 11 fentanyl analogs), were determined in 504 deidentified urine specimens with a positive immunoassay result for opiates (2,000 ng/mL morphine cutoff). The specimens were obtained in 2022-2023 from employees and applicants for safety or security sensitive positions in federally mandated testing programs. In addition, fentanyl prevalence was determined in 4,297 randomly selected specimens in 2017 and 2019.<br/>Results: Fentanyl prevalence in urine was 0.19%, which is similar to benzoylecgonine and twice that of morphine/codeine. In urine specimens with &lt;4,000 ng/mL morphine (n=214, 43%), fentanyl (22% co-positivity) was more prevalent than 6-acetylmorphine (10%). Prevalence of fentanyl was independent of the morphine concentration, while co-positivity of 6-acetylmorphne increased from 4% in specimens &lt;1,000 ng/mL morphine to 37% in specimens &gt;60,000 ng/mL.<br/>In 110 fentanyl positive specimens, median fentanyl concentration was 159 ng/mL (max 7,000) and median norfentanyl concentration was 1.520 ng/mL (max 34,600). In addition, para-Fluorofentanyl was detected in 50 fentanyl-positive specimens (45%). In 48/50 specimens, likely present as contaminant of illicit fentanyl production. <br/>Conclusion: Fentanyl may be a better marker of illicit opioid use than 6-acetylmorphine in urine specimens with morphine concentrations &lt;4,000 ng/mL. Norfentanyl concentrations are often 5-10 times higher than those of fentanyl, making norfentanyl a potential target analyte to identify fentanyl use. The only identified fentanyl analog was para-Fluorofentanyl, often present as a contaminant.

Topics

• impedance spectroscopy