Medicinal use of cannabis based products and cannabinoids

What you need to know: Cannabis based products for medicinal use contain cannabinoids derived from the cannabis plant, including ∆9-tetrahydrocannabinol (THC), cannabidiol (CBD), or a combination of THC and CBD. Synthetic cannabinoids for medicinal use typically mimic the effects of specific cannabinoids such as THC; THC is the constituent of cannabis that causes the “high,” whereas CBD is not intoxicating at typical doses. THC and CBD have contrasting mechanisms of action and therapeutic indications; THC carries a higher risk of adverse events compared with CBD; Rescheduling on 1 November 2018 permits some unlicensed cannabis based products to be prescribed for the first time in the UK, but only by doctors on the relevant Specialist Register of the General Medical Council; Indications for treatment, supported by evidence of low to moderate certainty, include chronic pain, some treatment resistant epilepsies, and nausea and vomiting caused by chemotherapy (table 2); Non-medicinal CBD products are legal and widely available on the internet and from health food retailers, but they lack quality standards and should not be used for medicinal purposes. Until recently, cannabis and its derivatives were widely restricted under legislation which stated they had no medical value and carried a substantial risk of misuse. Policy is rapidly changing, and cannabis can now be prescribed for medicinal use in many countries, including the UK. This provides important new opportunities for treating patients although these need to be weighed up against potential risks. Several different medicinal products exist, with contrasting mechanisms of action, efficacy, and safety. Use of these products may increase as new evidence arises and policy changes occur. Here we review this emerging field.