The synthetic opioid landscape continues to change as non-fentanyl-related substances appear in forensic toxicology casework. Among the newest synthetic opioids to emerge is isotonitazene, an analogue of a benzimidazole class of analgesic compounds. Isotonitazene is an active and potent synthetic opioid, but the extent to which this compound is causing toxicity among drug users was previously unknown. This report describes the confirmation and quantitation of isotonitazene in blood, urine and vitreous fluid through standard addition, as well as in vivo metabolic profile determination in drug users. Quantitative analysis was performed using liquid chromatography tandem mass spectrometry (LC–MS/MS), and metabolite discovery was performed using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). In total, 18 cases were confirmed positive for isotonitazene, nine of which were previously negative for any opioid. The average isotonitazene concentration in blood was 2.2 ± 2.1 ng/mL (median 1.75 ng/mL, range 0.4–9.5 ng/mL), and the average isotonitazene concentration in urine was 2.4 ± 1.4 ng/mL (median 2.7 ng/mL, range 0.6–4.0 ng/mL). The lowest concentration of isotonitazene in blood was 0.4 ng/mL (two cases) with no other opioids present; findings in death investigations. Four metabolites of isotonitazene were detected in vivo. N- and O-dealkylation products were determined to be the most prominent urinary biomarkers, while 5-amino-isotonitazene was identified in most blood samples. The prevalence and popularity of isotonitazene continue to increase in the United States in early 2020. Toxicologists, medical examiners and coroners should be aware of novel opioids outside the standard scope of testing, especially in medicolegal death investigations. Forensic scientists should add isotonitazene to testing procedures, and public health officials should counsel about potent new drugs and the dangers of opioid use.

中文翻译：

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真实法医案例中的异硝氮烯定量和代谢物发现。

随着非芬太尼相关物质出现在法医毒理学案例研究中，合成的阿片样物质格局继续发生变化。即将出现的最新合成阿片类药物是异硝氮烯，这是苯并咪唑类镇痛化合物的类似物。异硝氮烯是一种活性有效的合成阿片样物质，但该化合物在吸毒者中引起毒性的程度以前未知。本报告介绍了通过标准添加以及体内血液，尿液和玻璃体液中异硝氮烯的确证和定量吸毒者的代谢状况测定。使用液相色谱串联质谱（LC-MS / MS）进行定量分析，并使用液相色谱四极杆飞行时间质谱（LC-QTOF-MS）进行代谢物发现。总共确认了18例异硝氮呈阳性的病例，其中9例以前对任何阿片样物质呈阴性。血液中的异硝氮平均浓度为2.2±2.1 ng / mL（中位数为1.75 ng / mL，范围为0.4–9.5 ng / mL），尿液中的平均异硝氮烯浓度为2.4±1.4 ng / mL（中位数为2.7 ng / mL，范围0.6–4.0 ng / mL）。血液中异硝氮的最低浓度为0.4 ng / mL（2例），无其他阿片类药物存在。死亡调查的发现。在体内检测到四种异硝氮代谢产物。N-和O-脱烷基化产物被确定为最显着的尿液生物标志物，而在大多数血液样本中鉴定出了5-氨基-异tonitazene。到2020年初，异硝氮烯的流行和流行在美国继续增加。毒理学家，医学检查人员和验尸官应意识到标准检测范围以外的新型阿片类药物，尤其是在法医学死亡调查中。法医科学家应在测试程序中添加异硝氮烯，公共卫生官员应就有效的新药和使用阿片类药物的危险提出建议。