Since medical cannabis was legalised in the UK on the 1st of November 2018, thousands of patients have accessed these medications via private prescriptions. Still, the need for more evidence to support the safety and outcomes of patients prescribed medical cannabis products remains urgent. Over the last four years, the UK Medical Cannabis Registry (UKMCR) has collected real-world evidence from patients prescribed medical cannabis products for a range of indications, including fibromyalgia.
Fibromyalgia is a chronic disorder which is characterised by pain and tenderness throughout the body, fatigue, and trouble sleeping. People with fibromyalgia have a high sensitivity to pain. It is unknown what causes fibromyalgia and, as a result, diagnosis and treatment can be difficult. There is no cure for the condition.
Several treatments and therapies – including exercise and movement therapies, psychological and behavioural therapies, and medications – may be considered; however, multiple Cochrane systematic reviews on pharmacological approaches to fibromyalgia have concluded that the existing evidence is of poor quality and does not support the use of pharmacological treatments for fibromyalgia. Furthermore, opioids, which are commonly prescribed for fibromyalgia, carry a significant risk of abuse and adverse effects. There is, therefore, a need to identify alternative effective therapies for the treatment of fibromyalgia.
The endocannabinoid system (ECS) has been implicated in several important physiological and cognitive functions, including pain sensation and perception pathways. There is a growing trend towards patients seeking alternative treatments for pain management and other symptoms which may be relevant to fibromyalgia.
The increasingly widespread prescribing of medical cannabis for patients with fibromyalgia and other conditions, combined with growing clinical evidence makes the continued evaluation of cannabis-based medicines in these settings particularly important.
Data Collection by the UK Medical Cannabis Registry
The UK Medical Cannabis Registry, launched by Sapphire Medical Clinics in 2019, is the first registry in the UK to gather data on the outcomes of medical cannabis treatment, including product formulations, patient demographics, patient-reported outcome measures (PROMs), and adverse events (AEs). The current analysis assessed data from patients in the UK with fibromyalgia who had received cannabis-based medical products (CBMPs).
The data assessed in this study were reported electronically by patients or contemporaneously by clinicians during initial clinical consultations. PROMs from baseline to 1-, 3-, 6-, and 12 months were the primary outcome measure. Secondary outcomes were the incidence and severity of adverse events.
Patient-Reported Outcome Measures (PROMs)
PROMs were measured using Fibromyalgia Symptom Severity – a diagnostic criterion specific to fibromyalgia which combines widespread pain index (WPI) with symptom severity scale (SSS) scores. These scores give a total Fibromyalgia Symptom Severity between 0 and 31, with higher scores being associated with increased severity of both pain and auxiliary symptoms.
Visual Analog Scale – Pain (VAS-Pain), Single-Item Sleep Quality Scale (SQS), Generalized Anxiety Disorder-7 (GAD-7), EQ-5D-5L, and Patient Global Impression of Change (PGIC) were also used to measure PROMs.
The P-VAS questionnaire records patient-reported pain scores from 0-10. The SQS utilises a numerical rating scale rating from 0 (terrible) to 10 (excellent) to assess sleep quality over the past 7 days. The EQ-5D-5L is the HRQoL measure recommended by the National Institute for Health and Care Excellence (NICE). GAD-7 evaluates seven aspects of generalized anxiety by the number of days they were experienced in the past fortnight. The PGIC assesses perceived change since starting treatment in terms of activity limitations, symptoms, emotions, and overall quality of life, through two parts.
Participants were also asked to complete adverse events electronically at the time of their event, prior to completing PROMs, or during routine clinician follow-ups.
Results of the Analysis
A total of 306 patients with fibromyalgia were included for analysis. Of these, 253 (83.59%), 177 (58.42%), and 68 (22.22%) participants had been enrolled for a minimum of 3, 6, and 12 months, respectively. Recorded comorbidities included anxiety/depression (n = 166; 54.25%), arthritis (n = 98; 32.0%), hypertension (n = 38;12.42%), epilepsy (n = 5; 1.63%), and endocrine dysfunction (n = 40; 13.07%).
The results of the current analysis demonstrated an associated change in clinical outcomes in patients following prescription of CBMPs at up to 12 months. This included statistically significant changes in validated fibromyalgia-specific pain, sleep, anxiety, and health-related quality of life (HRQoL) scales.
Fibromyalgia Symptom Severity scores were observed to change from baseline up to six months. This finding was similar to previous studies that assessed the effects of CBMP using the Revised Fibromyalgia Impact Questionnaire. Participants also reported changes in pain severity, as demonstrated by the EQ-5D-5L-Pain and Discomfort scores and VAS-Pain scores.
HRQoL, as measured using the EQ-5D-5L index value, was seen to change at every follow-up compared to baseline.
Seventy-two participants (23.53%) reported 979 adverse events, the most common being fatigue (n = 75, 24.51%), dry mouth (n = 69, 22.55%), concentration impairment (n = 66, 21.57%), lethargy (n = 65, 21.24%), headache (n = 64, 20.92%), and somnolence (n = 59, 19.28%). Most adverse events were moderate (n = 436, 142.48%) or mild (n = 401, 131.05%) and none were considered life-threatening or disabling.
These results suggest an association between medical cannabis treatment and changes in fibromyalgia-specific symptoms, sleep, anxiety, and health-related quality of life. The authors note that more research – in particular, randomised controlled trials – are needed to examine causation and to add to our understanding of the full potential of CBMPs in clinical practice.