Introduction
Opioids are commonly prescribed for chronic pain management and although data support their role for managing acute and cancer-related pain, the evidence to support use in chronic pain is not robust.1–4 Prescription opioid misuse has contributed to a widespread opioid overdose crisis resulting in the deaths of hundreds of thousands of individuals worldwide.5,6
Medical cannabis containing different concentrations of cannabinoids – such as Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) – is increasingly being used for the management of chronic pain.7,8 Cannabinoids have a lower risk for dependence compared with opioids and the predicted median lethal dose for THC is >1000 fold higher than the effective dose.9–11 Previous studies have found that cannabinoids can improve pain related-outcomes, quality of life and, importantly, have an opioid-sparing effect.7,12–19 In addition, it has been reported that patients commonly use medical cannabis as a substitute for opioid medication.20–23However the effectiveness of cannabis substitution for opioids is not universally observed.24,25
Although these findings are noteworthy, the majority of clinical studies investigating cannabis and cannabinoids as substitutes or adjuncts to opioids are cross-sectional or small sample-size randomized controlled trials. This lack of high-quality evidence makes providing classical evidence-based recommendations inaccessible. Despite the paucity of clinical trial evidence, physicians and patients are using cannabis to support opioid tapering. In many countries, patients with chronic pain have access to cannabis, and patients have reported self-administering cannabis to reduce their opioid dose in the absence of clinical guidance.22,26,27
Although cannabis has a lower risk of dependence compared to opioids, it is not an inert therapy.28–31 At high doses, CBD-related side effects can include fatigue, diarrhea, and changes in appetite and weight.32 THC-related side effects can include sedation, syncope, tachycardia, risk of cannabis-use disorder, psychosis, and anxiety.8,33 With patients having access to prescribed cannabinoids and self-treating with cannabis to reduce their opioid dose, clinical guidance on safe cannabinoid initiation and titration is urgently required. Randomized placebo-controlled clinical trials examining how to co-manage cannabinoids and opioids are unlikely to be provided in the near future. Hence there is an immediate unmet need for guidance on this topic.34
To provide guidance to health care professionals on how to safely manage opioids and cannabinoids in patients with chronic pain, we employed a modified Delphi process to develop a consensus-based guidance algorithm. The modified Delphi process has been used extensively in health care settings to provide consensus-based recommendations surrounding important clinical questions.35 A previous Delphi study related to opioids and cannabis was undertaken between 2015 and 2016 and aimed to develop consensus guidelines for responding to patients on long term opioids using cannabis, however, the experts disagreed on many of the proposed topics.36
The purpose of the present initiative was to develop consensus-based recommendations on 1) when and how to safely initiate and titrate cannabinoids in the presence of opioids, 2) when and how to safely taper opioids in the presence of cannabinoids, and 3) how to monitor patients and evaluate clinical outcomes when treating with opioids and cannabinoids.