Studies on the metabolism of the fentanyl-derived designer drug butyrfentanyl in human in vitro liver preparations and authentic human samples using liquid chromatography-high resolution mass spectrometry (LC-HRMS).

Increasing numbers of new psychoactive substances (NPS) among them fentanyl derivatives has been reported by the European monitoring centre for drugs and drug addiction (EMCDDA). Butyrfentanyl is a new fentanyl derivative whose potency ratio was found to be seven compared to morphine and 0.13 compared to fentanyl.