Synthetic cannabinoids (SCBs) are a group of synthetic recreational drugs made with chemical compounds that are designed to act on the same neuronal receptors as tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana. These chemical compounds are different from THC, with distinct and unpredictable effects. This is generally because SCBs are direct agonists, while THC is a partial agonist of these receptors. Studies have also shown that SCBs and their active metabolites retain a higher affinity for the receptors they bind relative to THC, leading to increased toxicity.

SCBs may be sprayed onto plant material and smoked, mixed into a liquid and vaporized (vaped) or ingested. They are marketed under a variety of names including K2, Spice, Spice Diamond, Spice Gold, Space, herbal incense, Cloud 9, and Mojo, among others. SCB products are sometimes sold in convenience stores as aromatherapy agents and may be labeled "not for human consumption." Many variations are now identified as Schedule I controlled substances in the United States, although new varieties continue to appear on the market. Manufacturers frequently alter the chemical composition of the products in an effort to circumvent existing state and federal laws. Furthermore, SCBs are cheaper than THC, making them more accessible for use and increasing the risk that dealers may lace their supply of THC products with SCBs.

Tianeptine is an unregulated antidepressant not approved for use in the United States that can produce adverse effects and result in dependence. Per the US Centers for Disease Control and Prevention (CDC), the clinical effects of tianeptine abuse and withdrawal can mimic opioid toxicity and withdrawal. Elixir, tablet, and powder formulations are available for purchase (online and at gas stations / convenience stores) under many brand names (eg, Stablon, Tatinol, Coaxil, Neptune's Fix, Pegasus, Zaza, Tianaa). They may be adulterated with SCB receptor agonists or other drugs that can produce severe adverse effects. Be aware of potential tianeptine ingestion in patients with a history of opioid use disorder or dependence who present with altered mental status; other reported effects include tachycardia, hypotension, seizure, prolonged QT interval, prolonged QRS duration, and cardiac arrest.

Use of K2 and other SCBs is on the rise, especially among adolescents, young adults, undomiciled people, and incarcerated individuals. SCB toxicity is a particularly concerning public health issue. Outbreaks have been identified by clusters of emergency department visits and poison control center calls for illness due to SCB use. A recent study comparing SCB and botanical marijuana exposures reported to Texas poison control centers demonstrated 4 times more SCB poisoning reports. Clinical features of SCB poisoning vary and include neurologic, psychiatric, cardiovascular, and gastrointestinal symptoms. SCB poisoning can be fatal.

This summary is a general discussion of SCB poisoning. For information on serious bleeding and abnormal coagulation profiles associated with use of SCBs contaminated with brodifacoum, a long-lasting vitamin K antagonist used in rat poisoning, see synthetic cannabinoid-associated coagulopathy.

Related topics: e-cigarette or vaping product use-associated lung injury (EVALI), pediatric edible cannabis toxicity