利用液相層析串聯式質譜儀搭配人類肝臟微粒體鑑定依托咪酯和其一次代謝產物之二次質譜

Abstract

依托咪酯（Etomidate）原為臨床所使用的麻醉劑，近年來因為「喪屍煙彈」這種與電子煙併用的濫用形式在臺灣迅速蔓延。然而，目前臨床和法醫毒理學對於其代謝機制和特定生物標誌的理解仍不夠完整。 為了更深入了解依托咪酯在體內的變化，本研利用液相層析串聯式質譜儀（Liquid Chromatography-Tandem Mass Spectrometry, LC-MS/MS），並搭配人類肝臟微粒體（Human Liver Microsomes, HLMs）體外代謝模型，來模擬依托咪酯在人體肝臟中的第一級代謝，相較於目前已發表的文獻僅探討0至2小時的代謝時間，本研究在 0 到 168 小時之間，總共取了 9 個時間點，以更全面了解代謝物隨時間變化的趨勢，本研究首先使用全掃描(Full Scan)與選擇離子掃描(Selected ion monitoring)模式比對實驗組與對照組之圖譜，結合第一級代謝反應可能之反應途徑找出潛在的代謝物，再利用產物離子掃描模式(Product ion mode)分析其二次質譜之圖譜，並解析其可能之碎裂機制。 本研究主要發現六條主要的第一階段代謝途徑，這些代謝產物及其對應的質荷比（mass-to-charge ratio, m/z）如下： N-去烷基化（N-dealkylation, E1, m/z 141）、苯乙基去氫化（phenylethyl dehydrogenation, E2, m/z 243）、芳環羥基化（aromatic hydroxylation, E3, m/z 261）、乙氧基羥基化（ethoxy hydroxylation, E4, m/z 261）、雙羥基化（dihydroxylation, E5, m/z 277）、O-去烷基化生成依托咪酯酸（O-dealkylation to form etomidate acid, E6, m/z 217），從時間曲線上來看，依托咪酯酸在反應進行到第 4 小時的時候，濃度就已經超越了原型藥物，並在 24 小時達到高峰，證實了依托咪酯酸是監測依托咪酯濫用的潛在關鍵生物標誌。 綜上，本研究為臨床和法醫毒理學監測依托咪酯濫用提供更詳細的一級代謝路徑及質譜分析資訊，有助於未來更有效地應對「喪屍煙彈」這類新興毒品濫用的防治與規範。

Etomidate, originally developed as a non-barbiturate anesthetic for endotracheal intubation, has recently become widely abused in Taiwan through a new form of drug delivery known as “zombie vape,” where etomidate is illicitly mixed with electronic cigarette liquids. Despite its increasing prevalence as a substance of abuse, knowledge regarding its metabolic mechanisms and specific biomarkers remains limited in both clinical and forensic toxicology fields. To better understand the biotransformation of etomidate, this study employed liquid chromatography–tandem mass spectrometry (LC-MS/MS) in combination with an in vitro metabolic model using human liver microsomes (HLMs) to simulate phase I hepatic metabolism. Unlike previous studies that primarily focused on short incubation times ranging from 0 to 2 hours, this investigation extended the analysis to 168 hours, collecting samples at nine distinct time points to capture a more comprehensive view of time-dependent metabolite formation. Metabolite screening was initially conducted using full scan and selected ion monitoring (SIM) modes to compare chromatographic patterns between experimental and control groups. Potential metabolites were predicted based on plausible phase I reactions and subsequently confirmed using product ion mode to obtain MS/MS spectra and elucidate characteristic fragmentation pathways. This study identified six major phase I metabolic pathways of etomidate, corresponding to N-dealkylation (E1, m/z 141), phenylethyl dehydrogenation (E2, m/z 243), aromatic hydroxylation (E3, m/z 261), ethoxy hydroxylation (E4, m/z 261), dihydroxylation (E5, m/z 277), and O-dealkylation leading to the formation of etomidate acid (E6, m/z 217). Time-course analysis demonstrated that etomidate acid exceeded the concentration of the parent compound by the fourth hour and reached its peak at 24 hours, supporting its role as a potential biomarker for detecting etomidate use and abuse. In conclusion, this study offers a more detailed and extended characterization of etomidate’s phase I metabolism and its associated mass spectrometric signatures, providing valuable insight for clinical and forensic toxicology. The findings contribute to more effective monitoring and regulation strategies in response to the growing abuse of new psychoactive substances such as zombie vape.