Background: 3-Methoxyphencyclidine (3-MeO-PCP) and 3-methoxyrolicyclidine (3-MeOPCPy)
are two new psychoactive substances (NPS). The aims of the present study were the
elucidation of their metabolic fate in rat and pooled human liver microsomes (pHLM), the
identification of the cytochrome P450 (CYP) isoenzymes involved, and the detectability using
standard urine screening approaches (SUSA) after intake of common users’ doses using gas
chromatography-mass spectrometry (GC-MS), liquid chromatography-multi-stage mass spectrometry
(LC-MSn), and liquid chromatography-high-resolution tandem mass spectrometry (LC-HR-MS/MS).
Methods: For metabolism studies, rat urine samples were treated by solid phase extraction or simple
precipitation with or without previous enzymatic conjugate cleavage. After analyses via LC-HR-MSn,
the phase I and II metabolites were identified.
Results: Both drugs showed multiple aliphatic hydroxylations at the cyclohexyl ring and the
heterocyclic ring, single aromatic hydroxylation, carboxylation after ring opening, O-demethylation, and
glucuronidation. The transferability from rat to human was investigated by pHLM incubations, where Odemethylation
and hydroxylation were observed. The involvement of the individual CYP enzymes in
the initial metabolic steps was investigated after single CYP incubations. For 3-MeO-PCP, CYP 2B6
was responsible for aliphatic hydroxylations and CYP 2C19 and CYP 2D6 for O-demethylation. For
3-MeO-PCPy, aliphatic hydroxylation was again catalyzed by CYP 2B6 and O-demethylation by CYP
2C9 and CYP 2D6
Conclusions: As only polymorphically expressed enzymes were involved, pharmacogenomic variations
might occur, but clinical data are needed to confirm the relevance. The detectability studies showed that
the authors’ SUSAs were suitable for monitoring the intake of both drugs using the identified metabolites.