David J. Nutt, Lawrence D. Phillips, Michael P. Barnes, Brigitta Brander, Helen Valerie Curran, Alan Fayaz, David P. Finn, Tina Horsted, Julie Moltke, Chloe Sakal, Haggai Sharon, Saoirse E. O’Sullivan, Tim Williams, Gregor Zorn, and Anne K. Schlag
March 17, 2021
Medical cannabis has been legal in the UK since 2018, but it is not available on the NHS and is rarely prescribed. Project Twenty21 is taking steps to improve access to medical cannabis and one of the most common indications for medical cannabis is pain. One in 11 people in the UK suffer from chronic neuropathic pain but most doctors continue to prescribe drugs which can cause a significant reduction in quality of life due to negative side effects.
In this new paper, we report the results of a Multi-Criteria Decision Analysis (MCDA) which found that medical cannabis is among the most effective treatments for people with long term, problematic neuropathic pain.
The MCDA compares medical cannabis with the nine drugs that are most commonly prescribed for neuropathic pain in the UK, and evaluates them across 17 criteria.
The benefit-safety profile of medical cannabis was higher than for other commonly used medications and that patients taking cannabis-based medications would be less likely to experience many of the side effects, such as dependency or overdose, associated with more established treatments.
– David Badcock, CEO of Drug Science
Pharmacological management of chronic neuropathic pain (CNP) still represents a major clinical challenge. A group of expert clinicians (pain specialists and psychiatrists), scientists, and patient representatives convened to assess the relative benefit–safety balance of 12 pharmacological treatments, including orally administered cannabinoids/cannabis-based medicinal products, for the treatment of CNP in adults. This briefing document reports the inputs to an MCDA model developed by the group at a facilitated workshop in 2020 to consolidate the scientific evidence base with clinical and patient experience, and the output results.
What criteria are considered?
The inputs to an MCDA include the benefit and safety effect criteria, the treatment options, relative scores of the performance of each treatment on all the criteria, and weights reflecting the relative clinical relevance of the criteria themselves.
How are the criteria grouped?
The 17 effects criteria are shown here clustered under Benefits or Safety, with the latter clustered under Adverse Effects and Serious Adverse Effects.
How are the options scored on the criteria?
Participants scored all 12 options on each effect criterion using 0-100 scales, with 100 assigned to the most preferred option and 0 to the least preferred. This example is for the Pain Relief criterion. The numbers represent preference values for the average patient.
Here, the zero for ibuprofen means that it is the least preferred for pain relief, not that there is no pain relief, just as zero degrees Celsius does not mean no temperature.
What is swing weighting?
Some scales represent larger differences in clinical value than others, so they must be weighted to ensure that the units of preference on all 16 scales are equal. This is done by judging the swing in preference from zero to 100 on one scale compared to the zero to 100 swing on another. The key question is, “How big are the objective differences and how much are they clinically relevant?” For example, the difference in Quality of Life was judged to be clinically more important than the difference in Pain Relief, so QoL was given an arbitrary weight of 100.
What were the results?
Weights were normalised so all 17 summed to 1.0. Scores were then multiplied by the normalised weights and summed for each option to give an overall weighted preference score.
These are the overall weighted preference values for the 12 options. This shows that the three cannabinoids are best overall for their benefit-safety balance, with morphine and fentanyl least good.
Medical cannabis compared with common pain treatments
Weighted scores are shown here separately for Benefits and Safety. THC is overall best for Benefits while Safety is as good as or better than the non-cannabinoids, other than ibuprofen.
Comparing benefits to safety
This plot of Benefits versus Safety shows THC dominates the non-cannabinoids, that is, it is better in benefits and equal or better in safety.
Detailed effects comparison
This table shows the weighted scores for all effects. Green indicates the best effects for Benefits and Red shows the worst side effects for Safety. Of the non-cannabinoids, only duloxetine receives a green mark and no red ones. It is high scores for THC-CBD on Quality of Life and high scores on Safety that account for its dominance.
– David Badcock, CEO of Drug Science
For open-access to the full report of this research, see below: