A painful lesson: are we repeating previous mistakes in pain management?
Authors: Ian Hamilton, Suzanne H Gage
Journal: The Lancet Public Health (2018)

The idea that cannabis could be an alternative to opioids in the treatment of pain is attractive and gaining attention. The USA has witnessed a substantial rise in opioid-related deaths over the past decade, during which restricting the use of prescribed opioids has resulted in many people sourcing these opioids elsewhere, including from the illicit market.1James M Cunliffe J Décary-Hétu D Aldridge J Effect of restricting the legal supply of prescription opioids on buying through online illicit marketplaces: interrupted time series analysis.BMJ. 2018; 361: k2270PubMed Google Scholar For many patients, their journey to opioid dependency started when they were introduced to these drugs after surgery or as a way of managing acute and chronic pain.2Krebs EE Gravely A Nugent S et al.Effect of opioid vs nonopioid medications on pain-related function in patients with chronic back pain or hip or knee osteoarthritis pain: the SPACE randomized clinical trial.JAMA. 2018; 319: 872-882Crossref PubMed Scopus (507) Google Scholar There is clearly an incentive to find an alternative drug that has a lower risk of overdose or development of a dependency. But could cannabis or cannabinoids be a safer and more effective alternative? The answer according to Gabrielle Campbell and colleagues3Campbell G Hall WD Peacock A et al.Cannabis use, pain, and prescription opioid use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort study.Lancet Public Health. 2018; 3: e341-e350Scopus (127) Google Scholar seems straightforward—cannabis use did not reduce pain compared with no cannabis use for the patients with chronic non-cancer pain included in their prospective cohort study at 4-year follow-up. Compared with those who had not used cannabis, patients who used cannabis had greater pain severity score (relative risk ratio 1·14, 95% CI 1·01–1·29 vs 1·17, 1·03–1·32), greater pain interference score (1·21, 1·09–1·35 vs 1·14, 1·03–1·26), lower pain self-efficacy scores (0·97, 0·96–1·00 vs 0·98, 0·96–1·00), and greater generalised anxiety disorder severity scores (1·07, 1·03–1·12 vs 1·10, 1·06–1·15). Cannabis use also did not reduce their use of opioid medication. However, there are limitations to these observational findings. Although participants were asked about how many days they used cannabis for, we do not know if some people used once in a day or more than once. Any proof of concept, pharmaceutical trial, or licencing approval for a drug would need this detail to establish how often a drug should be taken. Likewise, we do not know what type of cannabis the participants used in this study. This fact matters, as cannabis varies in strength4Niesink RJ Rigter S Koeter MW Brunt TM Potency trends of Δ9-tetrahydrocannabinol, cannabidiol and cannabinol in cannabis in the Netherlands: 2005–15.Addiction. 2015; 100: 1941-1950Crossref Scopus (74) Google Scholar and, as with any analgesia, the dose needs to be matched to the severity of pain experienced. Insufficient information about the type and strength of cannabis is a common problem across all cannabis research,5Cuttler C Spradlin A Measuring cannabis consumption: psychometric properties of the daily sessions, frequency, age of onset, and quantity of cannabis use inventory (DFAQ-CU).PloS One. 2017; 12: e0178194Crossref PubMed Scopus (119) Google Scholar which could be improved by a standard assessment instrument based on an agreed measure of cannabis strength, in the same way that alcohol by volume is used to measure and describe the strength of alcohol. WHO recently reviewed the therapeutic potential of one particular cannabinoid—cannabidiol.6WHOCannabidiol (CBD): critical review report. World Health Organization, Geneva2018Google Scholar Although this review focuses on the potential benefits in relation to epilepsy, there is a brief mention of analgesia; however, the report suggests that the evidence for benefit is considerably less advanced for analgesia than for epilepsy.6WHOCannabidiol (CBD): critical review report. World Health Organization, Geneva2018Google Scholar In part, the WHO review is in response to the increasing number of countries permitting access to cannabis for medicinal use. This regulatory change can raise the expectations and hope for patients that cannabis will be an effective treatment for their health problems, including pain. We should not repeat the problems we now face with opioid prescribing, which originated from weak evidence that these drugs are effective in the management of chronic pain.7National Academies of Sciences, Engineering, and MedicineHealth and Medicine DivisionBoard on Health Sciences PolicyCommittee on Pain Management and Regulatory Strategies to Address Prescription Opioid AbusePhillips JK Ford MA Bonnie RJ Pain management and the opioid epidemic: balancing societal and individual benefits and risks of prescription opioid use. National Academies Press (US), Washington, DC2017Google Scholar One way forward would be to conduct a randomised controlled trial to investigate cannabis and its ability to control pain. Controlling and measuring the dose and type of cannabis used in such an experiment would be crucial for any comparison study and for applying the findings in practice. Unless we learn from the history of opioids and their use, we run the risk of replicating a non-evidence based approach to pain management, which will ultimately let down patients in need. We declare no competing interests. Effect of cannabis use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort studyCannabis use was common in people with chronic non-cancer pain who had been prescribed opioids, but we found no evidence that cannabis use improved patient outcomes. People who used cannabis had greater pain and lower self-efficacy in managing pain, and there was no evidence that cannabis use reduced pain severity or interference or exerted an opioid-sparing effect. As cannabis use for medicinal purposes increases globally, it is important that large well designed clinical trials, which include people with complex comorbidities, are conducted to determine the efficacy of cannabis for chronic non-cancer pain. Full-Text PDF Open Access