There have been a number of studies assessing the use of cannabinoids for acute pain following surgery, yet results remain mixed and uncertain. A recent systematic review aimed to further assess existing evidence of the analgesic efficacy of cannabinoid use in postoperative pain.

Cannabis has been used medicinally for thousands of years, with ancient Chinese texts outlining the use of the plant in early forms of anesthesia. Although there is abundant anecdotal evidence regarding the pain-relieving properties of cannabinoids, clinical evidence has been conflicting.

Following surgery, many patients experience acute postoperative pain, which is often managed with opioid medications. Given the risks widely associated with this class of medications, there is a need to assess the novel strategies to reduce post-operative prescribing.

What Evidence was Assessed?

A recent study by Canadian researchers analysed eight randomised controlled trials (924 patients) and four observational studies (4259 patients) which analysed the efficacy of cannabinoids for acute postoperative pain. The primary outcome assessed for effects in oral morphine equivalent consumption as well as the severity of pain at 24 hours post-operatively.

The researchers also considered the consumption of pain relief on the post-anesthesia care unit (PACU), as well as pain scores at 6 hours and 12 hours post-operatively. Opioid-related and cannabinoid-related side effects, patient satisfaction, and quality of recovery were also assessed as secondary outcomes of the review.

What Did the Studies Show?

Despite the aim of the review, there was insufficient data to provide a quantification of differences in cumulative oral morphine equivalent consumption and rest pain severity at 24 hours postoperatively, when compared to controls. In addition, there were no significant differences in total opioid use and or rest pain severity at 24 hours postoperatively, with the addition of cannabinoids to standard pain relief methods.

The Researchers’ Conclusions

The quantitative and qualitative assessment of the available literature suggests that the analgesic potential of cannabinoids in acute post-operative pain is limited. The researchers concluded that the studies and trials assessed in this review demonstrated that no clinically important benefits were identified when cannabinoids were added to traditional analgesic treatments for postoperative acute pain.

The results of this review do not support the routine use of cannabinoids as a post-operative analgesic treatment. In order to assess the full analgesic potential of medical cannabis products in postoperative pain, more studies and research needs to be carried out. A patient and public initiative of attitudes towards cannabis-based medicinal products by researchers from Imperial College London highlighted positive attitudes towards their further study in this setting.