Tetrahydrocannabinol (THC) is the psychoactive compound predominantly responsible for the intoxicating effects of cannabis plants. Officially named Delta-9-tetrahydrocannabinol, it stands as one of numerous cannabinoids found in cannabis. The chemical structure of THC facilitates its interaction with the body’s endocannabinoid system, particularly by binding to cannabinoid receptors in the brain and nervous system. This interaction is what triggers the effects typically associated with cannabis consumption.
The chemical formula for THC is C₂₁H₃₀O₂, denoting its composition of 21 carbon atoms, 30 hydrogen atoms, and 2 oxygen atoms. Structurally, THC comprises a phenolic ring, a bicyclic terpenoid, and a pentyl (5 carbon) chain. The molecule is characterised by a closed ring structure (the cyclohexene ring) and a benzene ring, forming part of what is described as THC’s tricyclic structure—central to its psychoactive properties.
THC’s interaction with the endocannabinoid system, especially the CB1 receptors in the brain, leads to the psychoactive effects experienced upon cannabis use. Such interaction affects various physiological processes, including pain sensation, mood, memory, and appetite.
The structure of THC closely relates to other cannabinoids in cannabis, such as cannabidiol (CBD), but critical differences in atomic arrangement lead to vastly different effects on the human body. Unlike THC, CBD does not produce psychoactive effects, underscoring the importance of chemical structure in determining the activity of different cannabinoids.
History and Discovery
THC was first isolated and synthesized in the 1960s by Israeli chemist Raphael Mechoulam and his team. This milestone in cannabis research paved the way for the discovery of the endocannabinoid system.
Legal and Regulatory Status in the UK
Since November 2018, THC products have been available on prescription to medical cannabis patients in the UK, marking a significant change in the legal landscape. However, recreational use of cannabis remains illegal, with THC being a controlled substance under UK law.
Methods of Consumption
THC can be consumed in various forms, including smoking cannabis flower, vaporising oils, ingesting edibles, and using tinctures. The method of consumption affects the onset and duration of effects, with inhalation providing rapid onset and edibles leading to longer-lasting effects. Please note that in the UK medical patients are requested to vape their medicine, with ‘smoking’ not considered a legal consumption method. Regardless of this many patients do still smoke their CBPMs.
Pharmacokinetics
Once consumed, THC is metabolised in the liver, producing metabolites that can exert additional effects. Its bioavailability and effects can vary greatly depending on the method of consumption and individual factors.
Clinical Applications in the UK
In the UK, THC-containing cannabis products are prescribed for conditions where other treatments have not been effective. This includes, but is not limited to, severe epilepsy, chemotherapy-induced nausea and vomiting, and chronic pain conditions. The use of medical cannabis, including THC, is tightly regulated and requires specialist recommendation.
Adverse Effects
Potential side effects of THC use include short-term memory impairment, altered judgement, coordination issues, and in some cases, anxiety or paranoia. Long-term or heavy use may have additional psychological and physiological impacts, underscoring the need for careful, medically supervised use.