6th January 2022
By Emily Ledger
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Despite the high prevalence of chronic pain (it is estimated that between 35.0-51.3% of the population may experience chronic pain at some time in their lives), the current treatment options are largely considered ineffective at managing the condition in the long term. They also often carry a significant risk of misuse, addiction, and overdose in addition to undesirable side effects.

Therefore, there is a serious need for alternative therapy and treatment options to manage the condition.

Increasingly, patients and clinicians alike are showing their interest in utilising the potential pain-relieving properties of the cannabis plant and its derivatives. Data collected through the UK Medical Cannabis Registry was recently assessed to determine how cannabis-based medical products (CBMPs) may be useful in the treatment of chronic pain and associated symptoms.

Medical Cannabis and Chronic Pain

Cannabis is an ancient crop that has been used medicinally – including for the treatment of pain conditions and as an anaesthetic – for thousands of years. However, the prohibition of cannabis led to a significant gap in our clinical knowledge of the plant. Nonetheless, a growing number of observational studies and randomised controlled trials are beginning to, once again, explore the potential of the cannabis plant and its derivatives in the treatment of chronic pain and other pain-related conditions.

Observational studies have identified associations between medical cannabis treatment and significant reductions in pain severity and interference and improvements in overall health-related quality of life measures. However, RCTs have largely been of indifferent quality, leading to conflicting conclusions. A growing number of patient registries have been set up to address the current gap in research.

Patient registries offer an increasingly important source of observational data, providing evidence in a resource-efficient manner within a real-world setting. The UK Medical Cannabis Registry (UKMCR) was established by Sapphire Medical Clinics in December 2019 to prospectively collect data of patient outcomes, allowing assessment of the benefit-risk profile of CBMPs for the treatment of a variety of medical conditions, including chronic pain.

The Current Data from the UK Medical Cannabis Registry

A number of outcome measures were used, including the Brief Pain Inventory short form (to measure pain severity), the Short-form McGill Pain Questionnaire-2, Generalised Anxiety Disorder-7 (used to generate a score for severity of anxiety), EQ-5D-5L tool (used to determine the overall health-related quality of life (HRQoL) score), the Sleep Quality Scale (SQS), and finally, the VAS-pain (a scale to capture how severely patients are experiencing their pain).

Of the total of 289 patients who had completed at least some quantity of the registry process, 190 were eligible for inclusion in the final analysis. Of these, 135 patients had recorded patient-reported outcome measures (PROMs) at 1 month, 68 had recorded PROMs at 3 months, and 44 had recorded PROMs at six months.

Outcome measures

Overall, patients exhibited statistically significant improvements at one, three, and six months in anxiety (GAD-7), sleep (SQS), the EQ-5D-5L pain and discomfort subscores and EQ-5D-5L Index Value. Furthermore, improvements were observed at months 1 and 3 for EQ-5D-5L mobility, and EQ-VAS subscores, while a significant improvement was observed at 1-month follow-up for EQ-5D-5L anxiety and depression subscores.

Statistically significant improvements were also observed in Brief Pain Inventory (BPI), SF-MPQ-2, and VAS scores across all time points.

These data from UKMCR demonstrate a potential association between medical cannabis treatment and improved outcomes in pain-specific and general health-related quality of life measures, over the short to medium term. Statistically, significant improvements were observed in multiple domains, including pain and discomfort, anxiety and depression, and sleep quality scales.

Of the patient sample, 43 (18.7%) patients reported at least one adverse event, with 20 (8.7%) patients reporting two or more adverse events. The most commonly reported adverse events were nausea (n=11; 5.8%) and fatigue (n=6; 3.2%). A significant proportion (49.3%) were considered mild, while 30.7% were moderate and 18.7% were severe.

The UKMCR also recorded the median oral morphine equivalent doses of patients prescribed opioid medications. At baseline, this median oral morphine equivalent was 24.0mg in this group. No significant differences were observed in oral morphine equivalent doses after one month; however, a significant reduction in median oral morphine equivalent was observed at three months (n=15; median of differences = -15.00mg), and six months (n=10; median of differences = -10.50mg).

Conclusions

The study concludes that treatment of chronic pain with CBMPs is associated with significant improvements in self-reported pain-specific and general HRQoL outcomes in the short to medium term in this patient cohort. However, they note that numerous limitations with the study design restrict the “capacity to draw definite conclusions regarding causality and the efficacy of treatment.”

Nonetheless, significant improvements were observed in relation to health-related quality of life, alongside an acceptable adverse event profile in comparison to other widely used treatment options for chronic pain. Furthermore, the apparent reduction in opioid doses also demonstrates promise, though further analysis in this area is required in the future.

Dr Simon Erridge, Head of Research and Access at Sapphire Medical Clinics, commented: “With the increasing number of prescriptions for medical cannabis in the UK, capturing patient outcomes and Real-World Evidence is essential for wider understanding and appropriate access for eligible patients.

“This is particularly true considering recent guidance from The Medicines and Healthcare products Regulatory Agency which aims to use Real-World Evidence to accelerate patient access to medicines through supporting clinical trials. The UK Medical Cannabis Registry hopes to play a leading role in this process.”

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