Brorphine-Investigation and quantitation of a new potent synthetic opioid in forensic toxicology casework using liquid chromatography-mass spectrometry.

New synthetic opioids continue to appear as novel psychoactive substances (NPS) on illicit drug markets. Isotonitazene emerged in mid-2019, becoming the most prevalent NPS opioid in the United States within a few months. Notification by the Drug Enforcement Administration of its intent to schedule isotonitazene in mid-2020 led to its decline in popularity and replacement with a new NPS opioid: brorphine. Brorphine is a potent synthetic opioid, but little information was previously available regarding its toxicity or involvement in impairment and death. Our laboratory developed an assay for the identification and quantitative confirmation of brorphine using standard addition. Quantitative analysis was performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In vitro and in vivo metabolism studies were performed using pooled human liver microsomes and authentic biological specimens, respectively, with analysis by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Brorphine was confirmed in 20 authentic forensic cases, commonly found in combination with fentanyl (100%) and flualprazolam (80%). The average concentration of brorphine in blood was 2.5 ± 3.1 ng/mL (median: 1.1 ng/mL, range: 0.1-10 ng/mL). The average concentration of brorphine in urine was 4.6 ± 7.6 ng/mL (median: 1.6 ng/mL, range: 0.2-23 ng/mL). The majority of cases originated from Midwestern states. Metabolism was verified to included N-dealkylation and hydroxylation. Detailed case histories and autopsy findings are presented herein. The prevalence of brorphine continues to increase in the United States. Forensic scientists should remain aware of the ongoing emergence of new opioids, especially those outside a standard scope of toxicology testing.