Postmortem distribution of etizolam in various autopsy samples using the surrogate analyte approach (SAA) method

Etizolam, a type of anxiolytic drug, is the most commonly abused drug among hypnotic/anxiolytic medications in Japan. Although there have been reports on the postmortem identification of etizolam in the blood, the detailed distribution of etizolam among organs in an abuse case has not been reported. In this study, we examined etizolam concentrations in the blood and organs obtained from etizolam-related autopsy cases using the surrogate analyte approach (SAA) method, which can be analytically used without blank samples. Target compounds were extracted from samples using the QuEChERS method and filtrated with Captiva ND Lipids. Then, the eluates were analyzed by LC-MS/MS. Etizolam-d₃ was used as a stable isotope-labeled surrogate compound with this quantification approach. A strong linear correlation was observed for each sample, showing a correlation coefficient value at least 0.99. The right heart, left heart, and femoral vein blood etizolam concentrations ranged from 85.2 to 178.2 ng/mL, while this concentration was 592.0 ng/g in liver tissue. Here, we could determine the etizolam concentration in various autopsy samples using LC-MS/MS. In addition, this work demonstrated that the SAA method can be successfully applied to various human samples.