Last year, the UK Government officially recognised the medicinal value of cannabis and acknowledged that it should be available on prescription (Torjesen, 2018). It announced that medicinal cannabis would be available via prescription from autumn 2018, but it has been more difficult than anticipated for patients to obtain it as a result of various barriers, such as the sparse evidence available regarding its risks and benefits (Robinson, 2019).
There are thousands of children and adults in the UK who are living with conditions that are not treatable by currently licensed drugs and for whom medicinal cannabis may be of benefit (Godlee, 2018). Medicinal cannabis has been found to help chronic pain, spasticity, nausea and vomiting, and epilepsy. There is new evidence of its use in anxiety, sleep disorders, reduced appetite during chemotherapy, fibromyalgia, post-traumatic stress disorder, Parkinson's disease, agitation in dementia, bladder dysfunction, glaucoma, and Tourette's syndrome, according to a prominent British neurologist (Godlee, 2018).
Dr Barnes was quoted in an editorial in the British Medical Journal clarifying that: ‘Serious side effects, including psychosis, are mainly linked to products with a high ratio of [tetrahydrocannabinol (THC)] to [cannabidiol (CBD)]’ (Godlee, 2018), and this particular claim has most recently been evidenced in a new study by Wall et al (2019).
What are researchers saying?
The recently published study in the Journal of Psychopharmacology has revealed that although cannabis does have some harmful effects on the areas of the brain involved in processing sensory and emotional inputs, CBD appears to serve as a buffer against these effects (Wall et al, 2019).
Functional magnetic resonance imaging (MRI) was used on 17 healthy volunteers who were experienced with cannabis, but not regular users (Wall et al, 2019). The scans took place after the participants took strains of cannabis with the main psychoactive component, Δ9-THC, and either high CBD or negligible CBD (Clinical Pharmacist, 2019). The volunteers who took the low CBD strain had disruptions in the brain in the regions responsible for emotional and sensory processing. The participants who took the high CBD strain, however, had minimal effects in these areas (Clinical Pharmacist, 2019).
These findings support the idea that THC is the cause of the harmful effects observed in cannabis users. Importantly, the authors point out that strong cannabis varieties have virtually no CBD, which appears to counteract negative effects on the parts of the brain studied, and are those linked with addiction and psychosis (Clinical Pharmacist, 2019). This information is important for prescribers who wish to advise their patients about various strains of medicinal cannabis and their risk and benefit profiles.
Another study published in the Journal of Palliative Medicine found that people living with cancer who use medical cannabis to treat their symptoms, such as neuropathic pain, have a tendency to favour strains with a higher ratio of THC to CBD, compared with patients who are taking the drug for conditions other than cancer (Kim et al, 2019).
Data were used from 11 590 adults who were licensed to receive medical cannabis in New York in 2016–2017, 1990 of whom were living with cancer (Kim et al, 2019). The researchers concluded that further studies are needed in order to understand the potential risks and benefits of cannabis for different conditions. The authors offered a possible explanation for the preference for high THC strains among people with cancer: the higher prevalence of neuropathic pain experienced by people living with cancer (Kim et al, 2019).
It is important to note, however, that the study did find that the THC:CBD ratio increased over time for both cancer and non-cancer patients (Kim et al, 2019). This would imply that a resistance does build up requiring higher doses, and this is important to know for prescribers providing relevant information to patients who are looking to make an informed decision about their treatment options.
What are politicians saying?
The evidence-base for medical cannabis is not substantial and although many patients are in need of prescriptions for various conditions, several barriers stand in the way of prescriptions becoming mainstream (Robinson, 2019).
In the House of Commons in April 2019, Secretary of State for Health and Social Care, Matt Hancock, was asked by Sir Mike Penning, Conservative MP for Hemel Hempstead, to ensure medical cannabis be made available on prescription throughout England (Robinson, 2019). The health secretary responded that the fact the drug is still not available to parents who feel it will benefit their children is a source of immense frustration (Robinson, 2019).
He has therefore ordered a ‘rapid evaluation’ from NHS England ‘to address barriers to clinically appropriate prescribing’ and has also requested that the National Institute for Health Research as well as industry take action towards improving the current evidence base (Robinson, 2019).
Sir Mike Penning raised the point that prescriptions for medical cannabis were in fact being issued by the ‘relevant experts’, but that NHS Trusts and clinical commissioning groups were refusing to honour those prescriptions (Robinson, 2019). Matt Hancock committed, however, that if a patient needs medical cannabis and a clinician signs off on that need, the prescription will be filled (Robinson, 2019).
Of course there are risks and benefits to all treatments, and the Secretary of State for Health and Social Care notes that as usual, it is up to clinicians to use their judgement regarding what is known about the drug, and what is needed for an individual patient (Robinson, 2019).
Health Education England is also developing a training package to provide the necessary information and support to clinicians looking to make the best, most informed prescribing decisions for their patients and the Health Secretary has said that this package should be available ‘imminently’ (Robinson, 2019).
To the future
Views, practices and laws are beginning to change around the world with regards to the use of medical cannabis, and as the evidence-base catches up, it will become less taboo to include medical cannabis as part of the range of possible prescriptions for various conditions.
‘Medicinal cannabis has been found to help chronic pain, spasticity, nausea and vomiting, and epilepsy’
Health Education England and the National Institute for Health and Care Excellence also urge prescribers to make use of the evidence search at https://www.evidence.nhs.uk, which provides open access to a synthesis of secondary evidence from over 800 sources, Clinical Knowledge Summaries, systematic reviews, the Scottish Intercollegiate Guidelines Network, the Cochrane Library, the royal colleges, Public Health England, and GOV.UK to everyone in the UK (Spring et al, 2018).
It also contains information from the British National Formularies, which importantly provide information on cannabis extract indications, side effects, drug interactions and contraindications – all of which will be important for non-medical prescribers to remain up-to-date with. Reviews are available via this evidence search on the use of cannabis in the treatment of epilepsy, neuropathic pain, fibromyalgia, HIV/AIDS, and asthma (Spring et al, 2018).