Practice

Medical cannabinoids

Scott A. McLeod and Jean-François Lemay
CMAJ July 31, 2017 189 (30) E995; DOI: https://doi.org/10.1503/cmaj.161395

The principal cannabinoids, cannabidiol and tetrahydrocannabinol, have different medical effects

Cannabidiol is nonpsychoactive, may reduce seizure frequency in refractory epilepsy and has preclinical evidence as a potential anxiolytic agent.1 Tetrahydrocannabinol (THC) and pharmaceutical combinations of THC and cannabidiol (nabiximols) show moderate evidence of benefit for chronic neuropathic pain.2 Tetrahydrocannabinol may induce memory deficits and psychotic symptoms; these symptoms may be reduced by combining THC with cannabidiol.1

Despite widespread availability, medical cannabinoids are still experimental

Most clinical trials use pharmaceutical cannabinoids rather than smoked THC.2 Although about 40% of the strains from licensed producers contain a potency of more than 15% THC, 9.4% is the highest percentage that has been studied to date.3 Smoked THC as a mode of delivery is not superior to oromucosal sprays based on current evidence, and may result in dose variability and unforeseen individual responses.2

Cannabinoids can increase the risk of motor vehicle collisions4

Road test trials have shown increased lane-position variability related to dosage.4 Combining cannabinoids with alcohol has been found to delay reaction times and increase time spent outside of lane.4 Effective strategies for driver education are needed to dispel false perceptions that cannabinoid-impaired driving is less of a risk than driving after alcohol use.

Cannabinoids should be titrated slowly with low initial dosing

Selection of dosages is individualized and experimental. Inquiring about quality of life and activity after cannabinoid use can help guide dosing. Appropriate selection of patients is important: patients with chronic pain and multiple sclerosis reported slightly improved quality of life with use of cannabinoids, whereas small declines were reported in patients with HIV.5 Dosage should be reduced if sedation or intoxication occur.

Users of medical cannabinoids may be vulnerable to psychosis

Dose-dependent associations exist between THC, psychosis risk and the earlier development of psychotic symptoms.1,2 Lower THC concentrations or balanced THC–cannabidiol content may optimize benefits while reducing harms for patients.3

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Footnotes

  • Competing interests: None declared.

  • This article has been peer reviewed.

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