Many patients are in need of medical cannabis, but the evidence base regarding its efficacy is sparse, and there are several barriers to break down before prescriptions can become mainstream (Robinson, 2019).
In April of this year, Health Secretary, Matt Hancock, was asked in the House of Commons by Sir Mike Penning, Conservative MP for Hemel Hempstead, to ensure that medical cannabis is made available on prescription throughout England (Robinson, 2019).
The health secretary responded that he found it immensely frustrating that the drug is still not available to parents who feel it will benefit their children (Robinson, 2019). He has called upon NHS England for a ‘rapid evaluation to address barriers to clinically appropriate prescribing’ and has also asked the National Institute for Health Research to take action towards improving the evidence base (Robinson, 2019).
Effects on the brain
Research to build up the evidence base is under way, and a new study published in the Journal of Psychopharmacology has shown that, while cannabis does have some harmful effects on the brain, cannabidiol (CBD) appears to bu?er the user against these effects (Wall et al, 2019).
The researchers used functional magnetic resonance imaging on 17 healthy volunteers who were experienced with cannabis but not regular users (Wall et al, 2019). The scans were recorded after these individuals took strains of cannabis with the main psychoactive component, Δ9-tetrahydrocannabinol (THC), and either high CBD or negligible CBD content (Clinical Pharmacist, 2019a). Interestingly, the study found that the volunteers who took the low-CBD strain had disruptions in certain areas of the brain, such as those involved in processing sensory and emotional inputs. The participants who took the high-CBD strain, however, had minimal effects on these regions (Clinical Pharmacist, 2019a).
This research supports the notion that THC is responsible for the harmful effects observed in cannabis users. The authors point out that strong cannabis varieties have virtually no CBD, which appears to counteract the negative effects on the parts of the brain studied—those linked with addiction and psychosis (Clinical Pharmacist, 2019a). This information is important for nurses in the community, who can inform patients who want to take medical cannabis about various strains and their potential risks and benefits.
Cancer vs. non-cancer
Another study, recently published in the Journal of Palliative Medicine, has reported that people living with cancer who use medical cannabis to treat their symptoms tend to favour strains with a higher or at least equal ratio of THC to CBD, compared with patients who are taking the drug for conditions other than cancer (Clinical Pharmacist, 2019b).
The study incorporated data from 11 590 adults who were licensed to receive medical cannabis in New York in 2016–2017, of which 1990 had cancer (Clinical Pharmacist, 2019b). The authors concluded that more research is needed to understand the benefits and risks of cannabis for various conditions, but proposed that one explanation for the preference for high-THC strains among people with cancer could be the higher prevalence of neuropathic pain experienced by this population (Clinical Pharmacist, 2019b).
However, it must also be noted that the THC:CBD ratio did increase over time for both cancer and non-cancer patients (Clinical Pharmacist, 2019b), implying that a resistance does build up, requiring higher doses, and this should be noted by nurses and other prescribers who will be advising patients about the drug in the future.