Analysis of Novel Synthetic Opioids U-47700, U-50488 and Furanyl Fentanyl by LC–MS/MS in Postmortem Casework

Following series of synthetic cannabinoid and synthetic cathinone derivatives, the illicit drug market has begun to see increased incidence of synthetic opioids including fentanyl and its derivatives, and other chemically unrelated opioid agonists including AH-7921 and MT-45. Among the most frequently encountered compounds in postmortem casework have been furanyl fentanyl (N-(1-(2-phenylethyl)-4-piperidinyl)-N-phenylfuran-2-carboxamide, Fu-F) and U-47700 (trans-3,4-dichloro-N-(2-(dimethylamino)cyclohexyl)-N-methylbenzamide). Both drugs have been reported to be present in the heroin supply and to be gaining popularity among recreational opioid users, but were initially developed by pharmaceutical companies in the 1970s as candidates for development as potential analgesic therapeutic agents. A method was developed and validated for the analysis of U-47700, U-50488 and furanyl fentanyl in blood specimens. A total of 20 postmortem cases, initially believed to be heroin or other opioid-related drug overdoses, were submitted for quantitative analysis. The analytical range for U-47770 and U-50488 was 1-500 and 1-100 ng/mL for furanyl fentanyl. The limit of detection was 0.5 ng/mL for all compounds. Within the scope of the method, U-47700 was the only confirmed drug in 11 of the cases, 5 cases were confirmed for both U-47700 and furanyl fentanyl, and 3 cases were confirmed only for furanyl fentanyl. The mean and median blood concentrations for U-47700 were 253 ng/mL (±150) and 247 ng/mL, respectively, range 17-490 ng/mL. The mean and median blood concentrations for furanyl fentanyl were 26 ng/mL (±28) and 12.9 ng/mL, respectively, range 2.5-76 ng/mL. Given the widespread geographical distribution and increase in prevalence in postmortem casework, toxicology testing should be expanded to include testing for "designer opioids" in cases with histories consistent with opioid overdose but with no traditional opioids present or insufficient quantities to account for death.