UWA has just concluded one of the largest and longest studies of medicinal cannabis use in a real-world setting.
Published 18 November 2022 in PLOS ONE, the study investigated the effects of orally ingested medicinal cannabis (MC) among almost 4,000 Australians, with a wide range of ages and conditions, who were prescribed the drug over a period of two years.
The researchers found that significant improvements for pain severity, mental health, insomnia, physical function, and emotional well-being and the improvements were sustained during those years, and determined that the drug is safe, well-tolerated and helpful for people experiencing these conditions.
Lead author, Associate Professor at UWA’s Medical School Dr Alistair Vickery, explained that even though randomised controlled trials (RCTs) are the gold standard for assessing pharmaceuticals, they have been challenging for MC due to the variety of products, the varying concentration and ratios of cannabinoids, and the generic nature of MC.
“We present up-to-date data from the Australian Emyria Clinical e-Registry (AECeR), which commenced in December 2018 and has monitored nearly 4,000 patients taking prescribed oral MC for up to 24 months,” Dr Vickery said.
“Patients who attended the national Emerald Clinics Network and were enrolled in the registry between December 2018 to April 2022 are all included in this analysis. This is the largest and longest real-world analysis of the efficacy and safety of GMP-like oral MC in a continuous enrolment cohort registry.”
The majority of the 888 patients who successfully completed the survey were prescribed oral MC for chronic pain related conditions (71.9%) and mental health disorders (15.4%), with other conditions including neurodegenerative diseases, irritable bowel syndrome and chronic fatigue syndrome.
A statistically significant improvement (at a p value of <0.001) was sustained across all outcomes, including clinical global impression (CGI-E, +39%: CGI-I, +52%), pain interference and severity (BPI, 26.1% and 22.2%), mental health (DASS-21, depression 24.5%, anxiety 25.5%, stress 27.7%), insomnia (ISI, 35.0%), and health status (RAND SF36: physical function, 34.4%: emotional well-being, 37.3%).
Dr Vickery, who is also a prescribing clinician with the Emerald network, explained that the median oral daily dose was 10mg for 9-tetrahydrocannabinol (THC) and 22.5mg for cannabidiol (CBD), with the total cannabinoid dose rising to 87.9mg, following careful titration over six months.
“Both dose and ratio remained stable for the remainder of the study, avoiding tachyphylaxis or dose escalation. No addictive or dependence behaviours were detected and there was no increase in concomitant medications,” he said.
“The median daily dose of oral THC for the AECeR cohort was approximately 10% of the average recreational user, and recreational cannabis, even for medical purposes, is inhaled. Inhaled cannabis is rapidly absorbed and reaches peak serum concentration in minutes giving the well-known ‘high,’ – in contrast, oral oils are slowly absorbed over hours.”
Of the 3,961 patients included in the analysis, 1,477 patients (37.3%) reported experiencing at least one adverse event deemed by the treating doctor to be ‘possibly,’ ‘likely,’ or ‘definitely related’ to the oral MC treatment.
“Oral MC was well tolerated, with fewer than 2% experiencing severe treatment related adverse events (TRAEs), and only two experiencing serious TRAEs – hallucination and mania,” Dr Vickery said.
For the other 37.3% of participants who experienced TRAEs, 67% of events were mild, and 31% were rated as moderate.
“This safety is particularly salient in contrast to the safety and tolerability of prescribed long-term opioids.”
Following regulatory access to the medical prescription of Good Manufacturing Product (GMP)-grade medicinal cannabis (MC) in November 2016, up to 100,000 Australians are now actively taking regularly prescribed MC.
The number of medicinal cannabis producers and products has rapidly increased, with at least 375 available MC products and brands, varying in ranges of ratios, profiles, concentrations, excipients, and delivery systems.
However, THC is still a ’Controlled Drug’ under Schedule 8 (S8) of the Poisons Standard, and CBD products (which are Schedule 4) must be prescribed by a registered medical practitioner and contain at least 98% CBD and 2% or less of other minor cannabinoids – including THC.
The authors highlighted that as MC products in Australia attract no government subsidy and little private subsidisation, with Department of Veteran Affairs subsidies available only for specifically approved conditions, the study cost participants an additional $AUD 2,000–4,000 per year.
Yet despite this, the retention rate in the AECeR was over 90% at six months and almost 70% by 12.