Over the last few decades, both prescription and illicit use of opioid-based drugs have become increasingly common, particularly in Western nations. In North America, the opioid epidemic is a public health crisis that continues to claim thousands of lives every year.
Opioid medications are often prescribed for both acute and chronic pain, despite limited evidence of their efficacy in the latter condition. This class of drugs carry a significant risk of dependence and harm, so alternative treatment options remain an important area of research.
The Opioid-Sparing Potential of Medical Cannabis
There is a growing literature base from lab-based investigations to in-human trials to support the use of medical cannabis for chronic pain in the right patient. For chronic pain, there is such a limited range of medications available to help with pain relief. Whilst exercise and psychological therapies can be helpful, they’re not a panacea and many people are still left debilitated on a daily basis and opioids are likely reached for by patients and doctors alike due to the lack of effective options.
There is also promising research suggesting a potential effect of specific cannabis compounds to ease opioid withdrawal symptoms, as well as reduce opioid consumption and cravings. However further research is required for this to be used outside of a clinical trial basis at present. A number of both human and animal studies have determined that medical cannabis could help to reduce pain when used both alone and in combination with opioids. The apparent synergistic effects of cannabis and opioids could lead to a reduction in opioid use, potentially reducing the risk of addiction and overdose. Other studies suggest that cannabis access laws may also have an impact on the number of opioids that are prescribed.
A recent matched cohort study carried out by researchers at the University of Alberta, Canada, aimed to add to this body of evidence.
Methods of the Study
A total of 5373 medical cannabis patients with a long-term opioid prescription were matched to controls who were all chronic opioid users. Adult patients who received medical cannabis authorisation in the province of Alberta between March 2013 and March 2018 were matched to controls who did not receive authorisation for medical cannabis.
The researchers hypothesised that “adult patients on chronic opioid treatment who are authorised to use medical cannabis would experience an opioid-sparing effect, defined as an overall decrease in oral morphine equivalence (OME) use over time compared to controls.”
All opioid doses across the patient sample were converted to OME based on each drug’s OME factor, days of supply, dispensation amount and strength. Weekly average OME for all medical cannabis patients were compared with matched controls for each week of the study in the six months prior to the index date and the 12 months following cannabis authorisation (or equivalent index date for controls).
Results of the Study
Over the 52-week follow-up period following medical cannabis authorisation, the researchers detected an initial decrease in the weekly average OME use in the medical cannabis sample in comparison to matched controls per patient.
While this difference was not considered to be significant, there was a consistent significant decrease in the week-to-week trend change after cannabis authorisation per patient. The results showed that authorisation for medical cannabis treatment had an intermediate effect on weekly OME in adults prescribed chronic opioids in Alberta. This change was found to be dependent on initial opioid dose.
All 5373 authorised medical cannabis patients were each matched with one control. Overall, 49.3% and 72.3% authorised medical cannabis and controls, respectively, ceased opioid consumption during the follow-up.
Patients prescribed low doses of opioid medications
Interestingly, the data showed that authorised medical cannabis patients who were prescribed low dose opioids (<50 OME) had a slight increase in their weekly OME per week following initial minimal decreases.
For patients prescribed <100 OME per week (the majority of the patient sample), no statistically significant decreases were observed in weekly OME. While it is possible that some of these patients may have decreased their opioid use over a longer period, this cannot be determined by this study.
Patients prescribed high doses of opioid medications
Among patients who were prescribed high doses of opioids (OME>100), a significant reduction in opioid consumption was observed. The researchers of this study considered a reduction of >400 OME among patients prescribed high doses of opioids to be potentially clinically significant.
The authors note that patients who were prescribed lower doses of opioids did not have substantial reductions may experience ‘floor effects’ whereby “minimal changes in opioid use can occur as their weekly OME, and therefore daily OME, is already very low”.
The researchers of this short-term cohort study conclude that these results find that “medical cannabis authorisation showed intermediate effects on opioids utilisation, which was dependant on initial opioid use.” Reductions in OME appeared to be greater and more significant in patients who were on a higher dosage of opioids (OME>100). The effects of medical cannabis in opioid reduction for those on low dose opioids appear to be limited according to this study.
These results contribute to the ongoing research into the potential impact of medical cannabis on pain management and as an alternative/adjunctive treatment to opioid medications. Further research in this area is warranted by clinicians and researchers to better understand the long-term potential benefits and harms of ongoing use.