Cannabis has been used medicinally for thousands of years, with evidence suggesting its use for a wide number of health-related indications, from headaches and seizures to nausea and pain. After almost 100 years of prohibition, cannabis is once again beginning to gain traction in the medical world, with researchers and doctors increasingly willing to explore the potential of the plant and its derivatives.
In this new climate – in which many countries have now legalised the medical use of cannabis – the most common reason for prescribing cannabis-based products is chronic pain.
A number of studies have aimed to understand the potential benefits and harms of using medical cannabis products in this capacity. Many of these studies were included in a recent systematic review and meta-analysis – the authors of which issued an accompanying BMJ Rapid Recommendation to provide contextualised guidance on the existing body of evidence.
A Clinical Practice Guideline
This guideline aimed to help answer the question ‘What is the role of medical cannabis or cannabinoids for people living with chronic pain due to cancer or non-cancer causes?’
While the most commonly reported reason for the prescription of medical cannabis and cannabinoids relates to chronic pain conditions, many physicians remain unsure of both the potential benefits and potential harms associated with the treatment. The researchers report that some in the industry have criticised the substitution of one addictive substance with questionable benefit (opioids) for another (cannabis).
However, sources including surveys and questionnaires have found that physicians are more open to receiving education on the potential of medical cannabis and cannabinoids for the treatment of chronic pain and a variety of other conditions.
A number of clinical guidelines have emerged in this area; however, the researchers note that these often present conflicting and inconsistent recommendations. For example, the recent recommendations, issued by the National Institute for Health and Care Excellence (NICE), made strong recommendations against “the use of medical cannabis for chronic pain outside of clinical trials.”
The authors of this most recent guidelines note that the limitations of clinical practice guidelines include limited or absent involvement of patients, failure to consider patient values and preferences to inform recommendations inadequate consideration and management of financial and intellectual conflicts of interest in panels, selected review of the evidence, and excessive use of strong recommendations in the face of low certainty or absent evidence.
Determining appropriate recommendations
A panel was put together consisting of general practitioners, a physical medicine and rehabilitation physician, internists, a paediatrician, a paediatric anaesthesiologist, pharmacists, physicians specialising in pain management, clinical pharmacologists, a chiropractor, a rheumatologist, methodologists, and people living with chronic pain (including a veteran).
Guided by the existing evidence – including surveys and guidance on outcome assessment – the researcher panel identified eight patient-important outcomes needed to inform their recommendation. These were: (1) pain relief, (2) physical functioning, (3) emotional functioning, (4) role functioning, (5) social functioning, (6) sleep quality, (7) opioid substitution, and (8) adverse events.
A number of adverse events were prioritised by the panel as part of their consideration for their recommendations. These were: cognitive impairment, vomiting, impaired attention, drowsiness, dizziness, nausea, and diarrhoea. The panel were also provided with evidence on the risk of long-term harms such as cannabis dependency, motor vehicle accident causing injury, falls, suicidal ideation, and suicide associated with medical cannabis or cannabinoids use for chronic pain.
The panel considered the balance of benefits, harms, and burdens of medical cannabis and the certainty of evidence for each outcome, typical and expected variations in patient values and preferences, and acceptability.
After making considerations for all aspects listed above, and more relevant factors, the panel issued a “weak recommendation to offer a trial of non-inhaled medical cannabis or cannabinoids, in addition to standard care and management (if not sufficient), for people living with chronic cancer and non-cancer pain.”
Understanding the Recommendation
This recommendation was reached using the evidence assessed by a linked series of four systematic reviews, in addition to reported patient values and preferences. The research panel found moderate to high certainty evidence that people with chronic pain have greater preference for balanced CBD:THC and high-CBD products in comparison to high-THC products. There is also evidence, however, that patients have concerns about the use of medical cannabis which are related to unwillingness to use cannabis – particularly with reference to the potential adverse effects, including addiction, tolerance, and losing control or usual behaviour.
The panel explains that their weak recommendation in favour of a trial of medical cannabis for the treatment of chronic pain reflects “a high value placed on very small to small improvements in self-reported pain intensity, physical functioning, and sleep quality, and a willingness to accept very small to modest risk of mostly self-limited and transient harms.
The authors of these recommendations emphasise that shared decision making is required to “ensure patients make choices that reflect their values and personal context.” It is also noted that current evidence warrants further investigation, the results of which may alter this recommendation.