A UK clinical review provides new interim advice for doctors and clinicians in prescribing cannabis-based products and cannabinoids to treat certain conditions.
Since a policy change in November 2018, specialist doctors registered with the UK’s General Medical Council (GMC), have been permitted to prescribe new medicines which derive from cannabis. Yet, research into these products has, to date, been limited creating an ‘information vacuum’ about these medicines, their benefits or harms.
A new review authored by leading scientists and clinicians from the University of Bath and University College London (UCL) points to the array of different cannabis-based products and cannabinoids available, and a clear need to educate both patients and clinicians into what these different products do and how they might help.
In particular, it points to important differences between products containing THC (the main psychoactive and intoxicating constituent of cannabis) versus CBD (the non-intoxicating element). Although in certain medicines CBD and THC are combined for clinical benefit, in others these components can work independently, playing different roles in improving certain symptoms.
For example, several studies have found that a combination of THC and CBD can alleviate symptoms of chronic pain, while CBD alone may be effective for treatment-resistant epilepsy. By contrast THC alone may be effective for treating nausea and vomiting caused by chemotherapy. THC and CBD are both ‘cannabinoids’ that act in different ways on the body’s endogenous cannabinoid system.
The cannabis plant produces over 144 different cannabinoids such as THC or CBD. Some medicinal products contain THC and/or CBD derived from the cannabis plant, while others contain synthetically produced cannabinoids. CBD is also available in non-medicinal products such as oils and tinctures.
Lead author, Dr Tom Freeman of the University of Bath’s Addiction and Mental Health Group explains: “In this complex and rapidly evolving field, there are several different cannabis-based and cannabinoid medicinal products. These differ in their THC and CBD content, who can prescribe them, and the conditions they may be used to treat. Here we provide an update for clinicians in advance of forthcoming NICE guidelines.
“A key message is that CBD products widely sold online and in health food shops lack quality standards and should not be treated as medicinal products.”
Research on cannabis was previously restricted because it was listed in Schedule 1, implying that it had no medical value. Cannabis was recently moved to Schedule 2 in the UK.
Freeman adds: “Research on unlicensed cannabis products has been limited to date. The rescheduling of cannabis and allocation of dedicated UK research funding will improve the evidence we have to guide clinical decision-making.”
Co-author, Dr Michael Bloomfield, head of translational psychiatry at University College London (UCL) added: “There have been leaps and bounds in our scientific knowledge in recent years, which combined with confusing claims about the medicinal uses of these drugs can be potentially perplexing for doctors and patients. We hope that our new guidance is helpful to doctors and patients worldwide. Much more research is needed into this new class of medicine.”
Co-author Dr Chandni Hindocha of the clinical psycho-pharmacology unit at UCL added: “Resources must be made available to update and educate clinicians about cannabis and cannabinoid based medicines. We would like to encourage doctors to maintain a compassionate and evidence-based approach when engaging with their patients in this rapidly developing field, in order to provide the best standard of care.”
Cannabis based products for medicinal use contain cannabinoids derived from the cannabis plant, including ∆8-tetrahydrocananbinol (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
Tom P Freeman, Chandni Hindocha, Sebastian F Green, Michael A P Bloomfield