Emergence of semi-synthetic cannabinoids in cannabis products seized in Eastern Denmark over a 6-year period.

Semi-synthetic cannabinoids (SSCs) are derivatives of phytocannabinoids with slight chemical modifications. SSCs have appeared as legal alternatives to tetrahydrocannabinol (Δ-THC) in recent years. This study investigates the prevalence of SSCs in seized drug samples from Danish police and custom authorities seized in Eastern Denmark in the period 2018-2023. Screening data obtained by gas chromatography-mass spectrometry (GC-MS) were reprocessed to enable detection of SSCs. Seized drug samples were categorized into six types of formulations. Δ-THC was the first SSC observed and appeared in 2019 followed by hexahydrocannabinol (HHC), tetrahydrocannabidiol (H4-CBD), hexahydrocannabinol acetate (HHC-O-Acetate), hexahydrocannabiphorol (HHCP) and tetrahydrocannabiphorol (Δ-THCP). Only one sample positive for SSCs was observed before the third quarter of 2021, with positive samples increasing from third quarter of 2022. Over the study period, a total of 15% (n = 216) of seized cannabis products were positive for SSCs. HHC was the most frequently identified SSC and found in 10% (n = 137) of samples, followed by H4-CBD at 4% (n = 53), Δ-THC at 3% (n = 44), and HHC-O-Acetate, HHCP, and THCP each at 1% (n = 10-20). SSCs appeared in 56% of E-cigarette products, 20% of hashish, 17% of concentrates, 10% of edibles, and 10% of plant materials. In conclusion, SSCs represent a new type of cannabinoids with a rapidly growing popularity and with specific compounds dominating at different periods. Some of the observed trends were likely influenced by the scheduling of HHC in May of 2023 in Denmark.