The increasing abuse of etomidate in South Korea led to its official designation as a controlled psychotropic substance on February 13 this year. To monitor this recent trend and prove retrospective exposure, a highly sensitive LC-MS/MS method was developed for the simultaneous determination of etomidate and its major metabolite (etomidate acid) in human hair.

Hair samples were washed, cut, and extracted with methanol by stirring overnight (14-16 h). The extracts were then analyzed by LC-MS/MS in positive electrospray ionization (ESI+) mode. The developed method exhibited excellent linearity (R² > 0.99) for all analytes within the quantitative range of 0.1-50 pg/mg, with limits of detection (LOD) of 0.1-1 pg/mg. Validation results demonstrated high reproducibility and recovery, with minimal matrix effects and carry-over. The validated method was successfully applied to 30 authentic hair samples from suspected abusers.The analysis revealed that etomidate was detected at concentrations of 0.736-31.855 ng/mg, and its major metabolite, etomidate acid, was detected at 0.005-0.358 ng/mg. These findings suggest that the proposed method is considered a suitable analytical approach for the simultaneous analysis of etomidate along with co-administered propofol in hair.