Adulteration of low-delta-9-tetrahydrocannabinol products with synthetic cannabinoids: Results from drug checking services.

Since late 2019, low-delta-9-tetrahydrocannabinol (THC) preparations adulterated with synthetic cannabinoids (SCs) have been frequently observed in Switzerland. The unawareness of users concerning the presence of SCs and the typically higher potency and toxicity of SCs, when compared with THC, can result in increased health risks. In Switzerland, low-THC (<1%) cannabis products, except hashish, are legal. These products can act as carrier materials for SCs. In this study, cannabis samples and user self-reports received through three drug checking services were collected and analysed, to gain deeper insight into this new phenomenon. Samples were collected from January 2020 to July 2021. Liquid chromatography coupled with high-resolution mass spectrometry was used for the qualitative screening and semi-quantification of SCs, while gas chromatography with flame ionization detector was applied for the quantification of THC and cannabidiol levels. Reported adverse effects were compared between users who consumed adulterated (SC-group) and non-adulterated (THC-group) products. Of a total 94 samples, 50% contained up to three different SCs. MDMB-4en-PINACA was most often detected. All adulterated cannabis flowers contained ≤1% THC. Adulterated hashish also typically presented low THC-levels (median: 0.8%). The SC-group was associated with higher numbers of adverse events (p = 0.041). Furthermore, psychologic (p = 0.0007) and cardiologic (p = 0.020) adverse effects were more profound in the SC-group than in the THC-group. Drug checking services enabled the timely detection and monitoring of new and potentially dangerous trends. Furthermore, due to user-reports, additional valuable information was gained on adverse events associated with the consumption of novel SCs.