BACKGROUND: The continuous introduction of new synthetic cannabinoid (SC) subtypes and analogues remains a major problem worldwide. Recently, a new "OXIZID" generation of SCs surfaced in seized materials across various countries. Hence, there is an impetus to identify urinary biomarkers of the OXIZIDs to detect their abuse.

METHODS: We adapted our previously reported two-pronged approach to investigate the metabolite profiles and disposition kinetics of 4 OXIZID analogues, namely, BZO-HEXOXIZID (MDA-19), BZO-POXIZID (5C-MDA-19), 5F-BZO-POXIZID (5F-MDA-19), and BZO-CHMOXIZID (CHM-MDA-19). First, bottom-up in vitro incubation experiments comprising metabolite identification, metabolic stability, and reaction phenotyping were performed using human liver microsomes and recombinant human cytochrome P450 enzymes. Second, top-down analysis of authentic urine samples from drug abusers was performed to corroborate the in vitro findings and establish a panel of urinary biomarkers.

RESULTS: A total of 42 to 51 metabolites were detected for each OXIZID, and their major metabolic pathways included N-alkyl and phenyl hydroxylation, oxidative defluorination (for 5F-BZO-POXIZID), oxidation to ketone and carboxylate, amide hydrolysis, and N-dealkylation. The OXIZIDs were metabolically unstable, mainly metabolized by cytochromes P3A4, P3A5, and P2C9, and demonstrated mechanism-based inactivation of cytochrome P3A4. Integrating with the results of 4 authentic urine samples, the parent drug and both N-alkyl and phenyl mono-hydroxylated metabolites of each OXIZID were determined as suitable urinary biomarkers.

CONCLUSIONS: Drug enforcement agencies worldwide may apply these biomarkers in routine monitoring procedures to identify abusers and counter the escalation of OXIZID abuse.