The Potential of Topical Cannabidiol for Thumb Basal Joint Arthritis

The Potential of Topical Cannabidiol for Thumb Basal Joint Arthritis

In recent years, access to cannabidiol (CBD) has broadened significantly throughout the world, including here in the UK. A multitude of CBD-based products can now be bought online and over-the-counter, as well as prescribed by medical professionals. As awareness around this cannabinoid continues to grow, so too does the number of patients seeking counselling on topical CBD for pain.

Over-the-counter vs. Medical-grade CBD

While over-the-counter CBD products can include muscle rubs, moisturisers, capsules, and oils, it is currently illegal for commercial brands to make any medical claims regarding these products. This is largely due to the relatively limited regulation of the industry (until 2022, there was no formal regulation of UK CBD brands). Nonetheless, many patients have aimed to manage their symptoms with the help of these products. 

The main difference between over-the-counter and medical-grade CBD products is the level of certification they must pass before being distributed to the public. For example, all CBD-based products intended for prescription in the UK and the EU must have been produced to Good Manufacturing Practices (GMP) standards. This helps to ensure the safety and quality of each medicine. Over-the-counter CBD products are not a substitute for approved medical products. 

Topical CBD for Pain

CBD, alongside tetrahydrocannabinol (THC), has been available for prescription for pain conditions since the rescheduling of cannabis in 2018. The change in the law allowed patients to be prescribed approved medical cannabis products by specialists for a wide variety of conditions – including arthritis. Here at Sapphire Medical Clinic, medical cannabis can be considered for the treatment of arthritis where first-line therapies have not achieved adequate symptom management.

While there is currently limited evidence to recommend the use of medical cannabis/CBD as a primary or sole treatment for arthritis, the results of some studies suggest that topical application of CBD could be useful for pain management. For example, one human clinical trial recently aimed to investigate the therapeutic potential of CBD for pain associated with thumb basal joint arthritis.

Design and Methods of the Study

Hand surgeons have seen a rise in the number of patients with thumb basal joint arthritis-related pain seeking counselling on the evidence for over-the-counter CBD use: in a survey of 103 patients, 69% were interested in trialling oral CBD and 80% were interested in trialling topical CBD for pain associated with thumb basal joint arthritis. 

With the results of this survey in mind, the researchers designed a randomised controlled clinical trial to test the effects of a CBD-based topical cream for arthritis-associated pain in comparison to placebo. Visual analog scale (VAS) pain scores were recorded as the primary outcome measure and physical performance metrics as secondary outcomes. The researchers hypothesised that topical CBD would have no effect on pain scores.

The active therapy was produced by dissolving pure 99.07% pure CBD isolate in shea butter until a CBD concentration of 6.2mg/mL was achieved. The placebo cream was made in the same way, with the omission of CBD. Participants (n = 18) were provided 1-mL syringes of either placebo or CBD/shea butter cream and directed to apply to their non-dominant thumb basal joint twice daily. A one-week washout period was then scheduled, followed by two weeks with the other cream.

Each patient was provided with a symptom diary for recording skin changes and other adverse events. The researchers also gathered data relating to study endpoints, including skin surveillance, vital signs, physical exam, outcome measures, C-SSRS scores, symptom diary evaluation, and laboratory tests.

Results of the Study

No skin changes, side effects, vital signs, C-SSRS scores, or laboratory abnormalities were identified at baseline, 1 week after CBD application or 1 week after washout. Furthermore, CBD was associated with significant improvements in VAS pain, Disabilities of the Arm, Shoulder, and Hand (DASH), and Single Assessment Numeric Evaluation (SANE) scores from baseline compared to the control arm. 

The mean VAS scores (range of 0-10) were 5 at baseline, 5 with the placebo cream, and 2 with the CBD cream (60% reduction); the mean DASH scores (range of 0-100, with a lower score indicating lower disability) were 36 at baseline, 31 with the placebo cream (14% reduction), and 22 with the CBD cream (39% reduction); the mean SANE scores (range of 0-100, with a higher score indicating greater global wellbeing) were 67.5 at baseline, 67.5 with the placebo cream, and 78.5 with the CBD cream (16% increase). All these scores exceeded the reported minimal clinically important differences for these parameters.

On the other hand, there were no identified differences in physical parameters (range of motion, grip, or pinch strength) during the study period. 

Researcher Conclusions

The researchers conclude that they have “demonstrated early short-term evidence that twice-daily topical CBD application results in significant improvement in patient-reported pain and patient-reported outcome measures, including VAS pain, DASH and SANE scores, without altering patient physical parameters”.

However, it is also noted that it remains challenging to place these results in context due to a scarcity of available human or animal data on cannabinoids for topical pain relief. They also address the limitations of their study, namely, the small sample size, short duration of follow up, and a lack of dose comparisons.

Nonetheless, this study presents promising results regarding CBD. It is recommended, however, that larger, multi-centre clinical trials are carried out to build on these findings and further investigate the safety, therapeutic potential, and dose-response of CBD for musculoskeletal pain.