Qualitative studies on the metabolism and the toxicological detection of the fentanyl-derived designer drugs 3-methylfentanyl and isofentanyl in rats using liquid chromatography–linear ion trap–mass spectrometry (LC-MSn)

Abstract

The opioid 3-methylfentanyl, a designer drug of the fentanyl type, was scheduled by the Controlled Substance Act due to its high potency and abuse potential. To overcome this regulation, isofentanyl, another designer fentanyl, was synthesized in a clandestine laboratory and seized by the German police. The aims of the presented study were to identify the phase I and phase II metabolites of 3-methylfentanyl and isofentanyl in rat urine, to identify the cytochrome P450 (CYP) isoenzymes involved in their initial metabolic steps, and, finally, to test their detectability in urine. Using liquid chromatography (LC)-linear ion trap-mass spectrometry (MS(n)), nine phase I and five phase II metabolites of 3-methylfentanyl and 11 phase I and four phase II metabolites of isofentanyl could be identified. The following metabolic steps could be postulated for both drugs: N-dealkylation followed by hydroxylation of the alkyl and aryl moiety, hydroxylation of the propanamide side chain followed by oxidation to the corresponding carboxylic acid, and, finally, hydroxylation of the benzyl moiety followed by methylation. In addition, N-oxidation of isofentanyl could also be observed. All hydroxy metabolites were partly excreted as glucuronides. Using recombinant human isoenzymes, CYP2C19, CYP2D6, CYP3A4, and CYP3A5 were found to be involved in the initial metabolic steps. Our LC-MS(n) screening approach allowed the detection of 0.01 mg/L of 3-methylfentanyl and isofentanyl in spiked urine. However, in urine of rats after the administration of suspected recreational doses, the parent drugs could not be detected, but their common nor metabolite, which should therefore be the target for urine screening.

Time-dependent postmortem redistribution of butyrfentanyl and its metabolites in blood and alternative matrices in a case of butyrfentanyl intoxication

“…Therefore, few phase I metabolites expected to occur in analogy to fentanyl [7] or 3-methylfentanyl [6] were included in the analysis of timedependent PMR. Phase II metabolites were not investigated, as their extraction from the biological matrices could not be expected with the applied sample preparation.…”

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)

“…Its chemical structure is depicted in Figure 1 and differs from fentanyl only by an additional methyl group. [11,12] Recently, metabolism of carfentanil, another potent fentanyl analogue typically used in veterinary medicine was described with N-dealkylation and piperidine hydroxylation as the major metabolic steps. While 3-methylfentanyl is methylated on the piperidine moiety, butyrfentanyl possesses an elongated alkyl side chain (one methyl group more compared to fentanyl).…”

In vitro characterization of potential CYP‐ and UGT‐derived metabolites of the psychoactive drug 25B‐NBOMe using LC‐high resolution MS

“…[25,26] Furthermore, these studies are now advantageously supported by the use of powerful software which helps in the elucidation of the metabolite chemical structures.…”