How Structural Variations in Synthetic Cannabinoids Affect Their Metabolism: A Pilot Study on the in Vivo Metabolism of 8 Synthetic Cannabinoid Receptor Agonists

The structural diversity and continuous emergence of synthetic cannabinoid receptor agonists (SCRAs) pose an important challenge to forensic and clinical toxicology. Understanding their metabolic pathways is essential for identifying reliable consumption biomarkers and improving toxicological screening strategies. This pilot study has investigated the influence of chemical structure on the metabolism of eight structurally diverse SCRAs: AMB-FUBINACA, ADB-FUBINACA, SDB-005, APINACA, CUMYL-4CN-BINACA, 5 F-AMB-PINACA, 5 F-AB-PINACA, and THJ-2201. The compounds were administered to male Sprague-Dawley rats from which serum and urine samples were analysed using liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). Metabolite identification was achieved through different analytical strategies. Following structural elucidation, the in vivo metabolism for each SCRA was evaluated, and the corresponding metabolic pathways were proposed. A comparative analysis of the different metabolic reactions was subsequently performed, classifying biotransformations according to the site of occurrence within the molecule, to highlight both shared features and compound-specific pathways. The results demonstrated significant variability in the number and type of metabolites identified, underscoring the substantial influence of chemical structure on SCRA metabolism. Despite this variability, consistent biotransformations across compounds were also observed. Notably, this in vivo study allowed the detection of several metabolites not previously reported in in vitro models, demonstrating the added value of in vivo approaches in profiling the complete metabolic fate of SCRAs.