Validation of an Analytical Method for Quantitation of Metonitazene and Isotonitazene in Plasma, Blood, Urine, Liver and Brain and Application to Authentic Postmortem Casework in New York City.

Starting in 2019, an emerging class of novel opioids causing public health concern was benzimidazole opioids, also known as "nitazenes". Two nitazenes, isotonitazene and metonitazene, were detected in postmortem samples received at the NYC Office of the Chief Medical Examiner. A protein precipitation extraction procedure was developed and validated for metonitazene and isotonitazene using 50 μL of blood, serum, liver, brain, and urine utilizing liquid chromatography-tandem mass spectrometry (LC-MS-MS). The limit of detection for both analytes was 0.10 ng/mL in plasma, blood, and brain, and was 1.0 ng/mL for urine and liver. The developed method was applied to authentic casework in which isotonitazene was detected in 10 cases between 2021 and 2022, with femoral blood concentrations ranging from 0.11 to 12 ng/mL. Metonitazene was detected in four cases in 2022 with concentrations ranging from 0.10 to 1.5 ng/mL in femoral blood. All but one case had the presence of fentanyl and/or fentanyl analogs, and the next most commonly encountered analyte in these cases was xylazine. The manner of death was accidental for all cases with a detected nitazene, and all but one case was attributed to mixed drug intoxications. None of the cases reported the identified nitazene compound as the sole intoxicant responsible for death. The opioid crisis continues to tear apart communities throughout the world, including New York City. Continued research and communication regarding these drugs helps to fight this crisis.