Cannabis users should wait 5 hours before driving; labelled cannabinoid content of many MC products is inaccurate; many Ontario GPs still lack confidence in MC
Cannabinoid research and findings for Wednesday, April 21, 2021
Welcome back to the CJMC Fortnightly for April 21. This morning, it’s John Evans, senior editor of the Canadian Journal of Medical Cannabis, bringing your rapid-fire summary of developments in research and medical use of cannabinoids in patient health.
This newsletter is a digital supplement to the Canadian Journal of Medical Cannabis, a publication for physicians based in Toronto, Canada. (We also organize the Real World Medicannabis conferences.)
Today's coverage covers how long MC-user’s driving skills are impaired (and that acronym is for medical cannabis, not motorcycle), inaccuracy in MC labelling, and remaining MC hesitancy among some general practitioners.
Driving impairment remains for 5 hours
Users of inhaled cannabis should wait at least five hours after consumption before engaging in safety-sensitive tasks such as driving.
These findings come from a systematic review that evaluated the acute effects of Δ9-THC on driving performance and driving-related cognitive skills (Neuroscience & Biobehavioral Reviews, July 2021; 126:175-193).
A total of 80 publications, covering 1,534 outcomes, were reviewed.
Overall findings
Meta-analyses of peak Δ9-THC effects showed impairment in multiple measures of driving performance and related cognitive skills
Regular cannabis users experienced lower impairment than 'other' (mostly occasional) users.
In the 'other' cannabis users data category, the magnitude of impairment—whether from inhaled or oral consumption—depended on dose, post-treatment time interval, and the performance domain being assessed
Models suggest that after inhaled consumption of 20 mg Δ9-THC, most driving-related cognitive skills would recover within approximately five hours
Impairment from oral consumption might take longer to subside
Cannabinoid levels on product labels inaccurate
Findings from a study of the urine of medical cannabis (MC) patients suggest that many of the cannabis products used were mislabelled regarding the THC and CBD contents.
Study format
97 adults aged 18-65 (mean age 39.6) years were included
Participants had expressed a desire to use cannabis for depression, pain, or insomnia
Assessments were done at baseline and 2, 4, 12, 24, and 48 weeks after initiating cannabis Tx
Assessments included urine samples, reports of recency of cannabis use, and the ratio of THC to CBD in the products used (THC dominant, CBD dominant, or approximately equal)
256 urine samples analyzed
Separate models were used to evaluate CBD and THC metabolites in the samples
Findings
Most participants were light users (53% used less than monthly) at baseline. During the study period, 39% to 47% used 3 to 4 days per week, 15% to 20% used 5 to 6 days per week, and 29% to 45% used daily
At least one cannabis metabolite was detected in 220 of the urine samples
No CBD metabolites were detected in 30.3% of samples from participants who said they used CBD-dominant strains, or in 37.0% of samples from those who used equal CBD-THC strains
No THC metabolites were detected in 10.9% of samples from those using THC-dominant strains or in 35.2% of samples from participants using equal CBD-THC strains
Vaping was the most common method of consumption
19.7% of samples from participants who reported vaping contained no measurable cannabinoid metabolites
CBD metabolites were more likely to be detected in samples from participants who consumed cannabis orally than in samples from those who vaped
THC metabolites were more likely to be detected in samples from participants who consumed cannabis orally or smoked it, than in samples from those who vaped
Key take-aways
Patients are not getting complete or accurate information regarding their cannabinoid exposure from the labels on products
Some vaping devices may not be heating cannabis appropriately to deliver cannabinoids to patients
Insights from the world of medical cannabis research
For Parkinson's disease (PD), animal investigations support suggestions of improvement in bradykinesia and/or tremors [with medical cannabis treatments], but human studies do not substantiate these findings. To date, research has shown the ability of cannabis to lessen motor and non-motor signs and symptoms of PD. [However], clinical trials have been conducted with small sample sizes, and there has been a lack of standardized clinical outcome measures—factors that fail to provide a solid foundation to support the use of cannabis as a therapeutic agent.
For Tourette's syndrome (TS), a few trials have yielded some positive findings. Essentially, the conclusion has been that there is reasonable, but not high-quality, evidence to support the use of cannabis as a treatment for TS.
—Dr. Colleen O'Connell, Assistant Professor, Division of Physical Medicine & Rehabilitation , Department of Medicine, Dalhousie University, Halifax, NB. (CJMC 2019; 1(3):14).
Some Ontario family doctors uncomfortable with MC
Some family physicians in Ontario, Canada, continue to be reluctant to authorize their patients to use medical cannabis, primarily due to a lack of knowledge about the medications and concerns about potential harms.
These findings come from a paper published in CMAJ Open (April 13, 2021; 9(2):E342-E348).
Eleven physicians agreed to be interviewed between Jan. and Oct. 2019. The investigators then applied thematic analysis to transcripts of the interviews and identified representative quotes.
Survey results
Three themes were identified: reluctance to authorize use, concern over harms and lack of practical knowledge
Participants had concerns about the limited evidence for, and their lack of education regarding, the therapeutic use of cannabis
Particular concerns included: harms associated with neurocognitive development, exacerbation of mental illness and drug interactions in older adults
Some participants thought medical cannabis was overly accessible and questioned their role following the legalization of recreational cannabis
What is next
The investigators suggest that family physicians may benefit from guidance and education that address the specific concerns surrounding medical cannabis, as identified by this survey.
Insights from the world of medical cannabis research
My approach [for managing pain in patients who are opioid-naive and those who wanted to go off opioids], is I start with CBD which can be helpful for pain, particularly for the associated problems of pain like sleep and anxiety. A good night's sleep and less anxiety do help pain and I think CBD can be somewhat analgesic in its own right. But then my view of pain is that we do often, and nearly always, in fact, need THC added in severe pain. Neuropathic pain particularly does need sometimes quite high THC. It is the only [kind of pain] I think that sometimes does need very quite high THC.
—Professor Mike Barnes, speaking at the U.K.'s Medical Cannabis Clinician's Society webinar “Real-world evidence for medical cannabis – too strong to ignore?” on Feb. 3, 2021. Dr. Barnes is a consultant neurologist and is the Chair of The Medical Cannabis Clinicians Society, Chief Medical Officer of Lyphe Group in London, U.K.
MC cost-effective for knee pain
According to findings published in Clinical Medicine Insights, medical cannabis (MC) could be a cost-effective approach to managing chronic knee pain. Arthritis and Musculoskeletal Disorders (March 16, 2021; 14:11795441211002492).
The investigators conducted a cost-utility analysis from a Canadian, single-payer perspective. They estimated quality-adjusted life years (QALYs) gained with one year of treatment with a range of MC and non-MC treatment approaches and calculated incremental cost-utility ratios (ICURs). Final ICURs were then compared to willingness-to-pay (WTP) thresholds ($66,714, $133,428, or $200,141 per QALY gained).
Treatments compared
MC oils or soft gels (oral), dried flowers (smoked)
Bracing
Glucosamine
Pharmaceutical-grade chondroitin
Oral NSAIDs
Opioids
Cost findings
MC oils and soft gels, at minimal or maximal dosing, were cost-effective compared to all current knee pain therapies at the lowest WTP threshold
MC dried flowers were only cost-effective up to 0.75 and 1 g/day (by mean and median estimates, respectively at the first two WTP thresholds, but were cost-effective at all dosages at the $133,428/QALY gained threshold
Final caveat
While their findings do show MC treatments to be cost-effective in treating knee pain, the authors note that the evidence on the medical use of cannabis remains limited and predominantly of low quality. They say that additional trials on MC are definitely needed, specifically in patients with chronic knee pain.
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