A single dose of vapourised cannabis has no clinically meaningful effect on airway function, exertional breathlessness and exercise endurance in people with advanced COPD, Canadian researchers report.
The single-centre, randomised, cross-over study published in the Annals of the American Thoracic Society involved 16 patients who inhaled vaporised cannabis (extracted from 35 mg of 18.2%-THC dried marijuana) or placebo via an inhaler.
Participants were instructed to inhale for 5 seconds, hold the vapour in their lungs for 10 seconds and wait 40 seconds before repeating the puff cycle. The control group inhaled vapour from a dried herbal product containing trace amounts of THC and cannabidiol.
Results showed that cannabis had no effect on breathlessness intensity ratings at isotime or on exercise endurance time.
Four participants had a cannabis-induced decrease in breathlessness intensity ratings at isotime by the minimally clinically important difference (MCID) of ≥1 Borg unit compared with the remaining 12 participants who did not respond.
Two participants had a cannabis-induced increase in exercise endurance time by the MCID of ≥101-sec compared with the remaining 14 participants.
The researchers also found a “modest but significant” within-treatment effect of inhaled cannabis on psychoactivity, including decreased anxiety, feeling high, drunk and stoned.
“Future studies should utilize existing cannabinoid preparations (e.g CBD) that do not affect psychoactivity but act on cannabinoid receptors to assess changes in airway function, exertional breathlessness and exercise endurance in COPD,” they said.
The small study size and the inclusion of only stable, symptomatic patients with advanced COPD limited the generalisability of the study, the researchers noted. Furthermore, the control cannabis may also have not served as a “true” control as it had traces of CBD.
“Larger randomized clinical trials with more participants are needed to draw definitive conclusion regarding the effect of inhaled vaporized cannabis on exertional breathlessness, exercise endurance time, and cardiopulmonary physiologic parameters in adults with COPD,” they wrote.