Long-term stability of novel synthetic opioids in blood.

Recently, there has been an increase in overdose deaths due to novel synthetic opioids (NSO). Due to backlogs experienced by many forensic laboratories, it is important to understand drug stability in a variety of storage conditions. The objective of this study was to investigate the stability of AH-7921, U-47700, U-49900, U-50488, MT-45, W-15, and W-18 in blood at various temperatures over a 36-week period. NSO were generally stable over the 36-week period (66%-118%) at low and high concentrations when blood samples were stored in the refrigerator or freezer. Most analytes were stable for at least 2 weeks at room temperature (77%-120%). At the elevated temperature (35°C), analytes were generally stable for at least 14 days (75%-109%). This study has determined the stability of several NSO at various temperatures over a 36-week period. These results reflect the forensic significance of keeping samples stored at proper temperatures. Blood samples suspected to contain synthetic opioids should be stored refrigerated or frozen, when possible, in order to preserve analyte stability, especially at low concentrations.