"Synthetic cannabinoids, also known as synthetic cannabinoid receptor agonists, are a group of drugs that mimic the effects of a substance found in cannabis called tetrahydrocannabinol (THC). THC is responsible for many of the psychoactive effects of cannabis which give that feeling of being ‘stoned’ or ‘high’ (Gaoni and Mechoulam, 1964; Huestis et al., 2001; Pertwee, 2005a; Pertwee, 2014). These effects are caused by activating a receptor in the brain called the cannabinoid receptor type 1 (CB1 receptor) (Huestis et al., 2001; Pertwee, 2014). The receptor is part of a signalling system in the body called the endocannabinoid system, which helps regulate, among other things, behaviour, mood, pain, appetite, sleep and the immune system (Pertwee, 2015).

"Similar to the fentanils, the synthetic cannabinoids were originally developed by scientists to study the body, provide insights into disease and help develop new medicines (Pertwee, 2005b; Reggio, 2009). Around the mid-2000s, they began to appear in Europe in products called ‘Spice’ that were sold as ‘legal’ replacements to cannabis. In these products, powders containing synthetic cannabinoids were mixed with plant material which could then be smoked as cigarettes (‘joints’) (Auwärter et al., 2009; EMCDDA, 2009; Jack, 2009). Since then, 179 cannabinoids have been identified on the drug market in hundreds of different products (Figure 7). The products are commonly referred to as ‘herbal smoking mixtures’, ‘Spice’, ‘K2’, ‘synthetic cannabis’ and ‘synthetic marijuana’. Most of the synthetic cannabinoid powders are made in China, with the final products made in Europe.

"Because synthetic cannabinoids work in a similar way to THC, many of their effects are similar to those of cannabis (Auwärter et al., 2009). Most prominently, they are able to create the feeling of being ‘stoned’. This includes relaxation, euphoria, lethargy, depersonalisation, distorted perception of time, impaired motor performance, hallucinations, paranoia, confusion, fear, anxiety, dry mouth, bloodshot eyes, tachycardia (an abnormally fast heart rate), nausea and vomiting. In some cases, these effects appear to be much more pronounced and severe than those produced by cannabis (Ford et al., 2017; Zaurova et al., 2016)."

Source

European Monitoring Centre for Drugs and Drug Addiction (2018), Fentanils and synthetic cannabinoids: driving greater complexity into the drug situation. An update from the EU Early Warning System (June 2018), Publications Office of the European Union, Luxembourg.
http://www.emcdda.europa.eu/p…
http://www.emcdda.europa.eu/s…