“Cannabis sativa” by Manuel is licensed under CC BY 2.0

COPD: Vaporized Cannabis Did Not Reduce Breathlessness or Improve Exercise Capacity

MedicalResearch.com Interview with:

“Cannabis sativa” by Manuel is licensed under CC BY 2.0


Sara Abdallah, PhD Student, first author and
Dennis Jensen, PhD Associate Professor,
Department of Kinesiology and Physical Education
Associate Dean – Infrastructure, Faculty of Education
Director, McGill Research Center for Physical Activity and Health
Canada Research Chair in Clinical Exercise & Respiratory Physiology
Associate Member, Translational Research in Respiratory Diseases Program
Research Institute of the McGill University Health Center

MedicalResearch.com: What is the background for this study? What are the main findings? 

Response: Many patients with chronic obstructive pulmonary disease (COPD) suffer from severe breathlessness at rest and on minimal exertion despite receiving optimal drug therapy for their underlying disease (e.g., bronchodilators). In these patients, breathlessness significantly diminishes exercise capacity and quality of life. Thus, research focused on identifying adjunct therapies for management of breathlessness in patients with advanced COPD is clinically relevant.

A series of studies conducted in the 1970’s found that smoked cannabis caused bronchodilation (i.e., improved airway function) in healthy individuals and in patients with asthma. More recently, it has been demonstrated that delta-9 (∆9)-tetrahydrocannabinol (THC, the major cannabinoid constituent of cannabis) inhibits cholinergic contractions in isolated human bronchi and that a positive association exists between measure of lung function (e.g., forced expiratory volume in 1-sec) and cannabis use in patients with COPD. These studies lead us to hypothesize that inhalation of vaporized cannabis may alleviate exertional breathlessness and improve exercise tolerance in patients with advanced COPD by improving airway function at rest and during exercise.MedicalResearch.com: What should readers take away from your report?

Response: We compared the acute effects of 35 mg of cannabis (18.2% THC) vs. 35 mg of control cannabis (i.e. cannabis devoid of THC) administered using the Volcano Digit® vaporizer on airway function, exertional breathlessness and exercise capacity in 16 patients with advanced COPD and severe breathlessness despite receiving dual or triple inhalation therapy (long-acting muscarinic antagonist and long-acting beta2-agonist bronchodilator with or without an inhaled corticosteroid) for their underlying lung disease. We found that, compared to the control cannabis, inhaled vaporized cannabis did not have a statistically significant or clinically meaningful positive or negative effect on airway function, exertional breathlessness or exercise capacity. Nevertheless, we observed heterogeneity in responsiveness to inhaled vaporized cannabis. For example, 4 of the 16 patients had a clinically significant decrease (improvement) in breathlessness intensity ratings during exercise following inhalation of vaporized cannabis vs. control. The remaining 12 patients had no change (5 patients) or worsening (7 patients) of their breathlessness during exercise following inhalation of cannabis vs. control. Finally, measures of cognitive function, psychoactivity and mood were not significantly different after inhalation of vaporized cannabis vs. control. 

MedicalResearch.com: What recommendations do you have for future research as a result of this work? 

Response: Larger randomized clinical trials with more participants are needed to draw definitive conclusions regarding the effects of vaporized cannabis on airway function, exertional breathlessness and exercise capacity in patients with COPD. Future studies should evaluate the effects of other doses, modes (e.g. orally administered cannabis), types (e.g. various cannabinoids in different ratios), and regimes (e.g. single dose vs. repeat-dose) of cannabis in patients with mild-to-moderate and severe COPD. 

MedicalResearch.com: Is there anything else you would like to add?

Response: This is the first clinical trial to demonstrate that single-dose inhalation of vaporized cannabis can no clinically meaningful positive or negative effect on airway function, exertional breathlessness and exercise capacity in patients with advanced COPD. The results of this clinical trial should be interpreted with caution and should not be extrapolated to other doses, modes and types of cannabis, nor to other patient populations.

This trial was supported by an Investigator-Initiated Study grant from Tilray (Nanaimo, BC, Canada


Annals of the American Thoracic Society

Effect of Vaporized Cannabis on Exertional Breathlessness and Exercise Endurance in Advanced COPD: A Randomized Controlled Trial

Sara J Abdallah , Benjamin M Smith , Mark A Ware , Michelle Moore , Pei Zhi Li , Jean Bourbeau ; Dennis Jensen
Published Online: July 27, 2018

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Last Updated on July 30, 2018 by Marie Benz MD FAAD