Analysis of the Illicit Opioid U-48800 and Related Compounds by LC-MS-MS and Case Series of Fatalities Involving U-48800.

We report a method for the detection and quantitation of 12 drugs and 2 metabolites in the same structural class as the illicit mu-opioid agonist U-47700 in human whole blood. These substances are either known or suspected to be present as potential novel opioids in illicit drug markets. The general class of these drugs was developed in pharmaceutical research programs in the 1970s, but these drugs have recently become of concern for overdoses and death in opioid users in the USA and internationally. The scope of analysis included the following compounds: methylenedioxy U-47700, ethylenedioxy U-47700, ethylenedioxy U-51754, U-69593, U-47931E (bromadoline), U-47700, U-48800, U-49900, U-51754, U-50488, propyl U-47700 and isopropyl U-47700. Additionally, two metabolites N,N-didesmethyl U-47700 and desmethyl U-47700 were also included in the scope. Drugs were extracted from human whole blood using solid-phase extraction, and the extracts were analyzed by liquid chromatography--tandem mass spectrometry. The assay was validated with respect to bias, carryover, interference, within-run and between-run precision, and accuracy. Eight medicolegal death investigation cases that had screened positive for U-48800 by liquid chromatography--time-of-flight mass spectrometry were successfully confirmed and quantified using this method. The mean and median concentrations of U-48800 in these cases were 2.5 (±2.1) and 1.8 ng/mL, respectively, with a range of concentrations of 0.27-6.2 ng/mL. Case history information including the presence of other drugs in combination are described and discussed.