Retrospective fentanyl analysis in the hair of workplace drug testing subjects

The powerful opioid analgesic fentanyl has become readily available in the most recent phase of the ongoing opioid crisis. While fentanyl does have important medicinal uses, it is highly prone to misuse and nonmedical use. In addition, the relative ease of fentanyl synthesis lends it subject to structural modifications by clandestine chemists to produce fentanyl analogs (often termed fentalogs) that are designed to evade detection by law enforcement and forensic toxicologists. Herein, we report fentanyl data as measured by liquid chromatography-tandem mass spectrometry (LC-MS-MS) with extensively washed hair as the matrix in the USA workforce population over the years 2019-24. The limit of detection and limit of quantitation for our method was set at 1.0 pg analyte/mg hair. From our data, we find that ∼94% of samples with concentrations >150 pg fentanyl/mg hair contained measurable norfentanyl metabolite above 1.0 pg/mg hair. In our studied population, only one sample containing the presence of a fentanyl analog was observed in the absence of fentanyl itself. It thus appears that fentanyl analogs are most often found in combination with, or as contaminants of, fentanyl consumed by our study population.