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 (Δ⁹-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. Δ⁸-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 (Δ⁹-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), Δ⁸-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.