LAUSR

Valerylfentanyl-a novel synthetic opioid, less potent than fentanyl, has been reported in biological samples, but there are limited studies on its pharmacokinetic properties. The goal of this study was to elucidate the metabolism of valerylfentanyl using an in vitro-human liver microsomes (HLM) model compared to an in vivo-zebrafish model. Nineteen metabolites were detected with N-dealkylation-valeryl norfentanyl and hydroxylation as the major metabolic pathways. The major metabolites in HLM were also detected in 30 days post fertilization zebrafish. An authentic liver specimen which tested positive for valerylfentanyl, among other opioids and stimulants, revealed the presence of a metabolite which shared transitions and retention time as the hydroxylated metabolite of valerylfentanyl but could not be confirmed without an authentic standard. 4-anilino-N-phenethylpiperidine (4-ANPP)-a common metabolite to other fentanyl analogues was also detected. In this study we elucidated the metabolic pathway of valerylfentanyl, confirmed two metabolites using standards, and demonstrated the zebrafish model produced similar metabolites to the HLM model for opioids.