In reply: Comment on: Patient-reported outcomes in those consuming medical cannabis: a prospective longitudinal observational study in patients with chronic pain

Abstract

To the Editor, We thank Dr. Vitetta and Mr. Sikali for their interest in our longitudinal study of cannabis products for the management of chronic pain. Their letter highlighted a major concern for the lack of well-defined good manufacturing practice certifications for cannabis products. The lack of reliability in cannabinoid content raises the question as to whether a product used is consistent for all patients and implies that differences within even the same product batch would likely affect efficacy, side effect profile, tolerability, and attrition rates in studies. At this time, the only cannabinoid products that have a drug identification number as regulated by Health Canada are nabilone (Cesamet ) and nabiximols (Sativex ). These products are rigorously tested as mandated by the governing federal body to ensure content quality and patient safety. Similar Health Canada measures do not exist to ensure content quality for plantbased cannabis products. These are approved under a separate law, the Cannabis Act and its predecessors, and are legal in Canada. There is no variability limit for dried cannabis, and potency levels vary between parts of the plant as well as between plants within a specific lot or batch. In a study examining the labelling accuracy of cannabidiol extracts sold online based on 84 products from 31 companies, 42.85% of products were under-labelled ([ 110% of labelled content) and 26.19% were over-labelled (\\ 90% of labelled content), leaving only 30.95% of products within the labelled range (90–110% of labelled content). This inconsistency is concerning and represents one of the challenges that patients and providers encounter when attempting to use cannabis as a medicine in North America. Nevertheless, we will take this opportunity to stand behind our study results; rarely does a product being trialled end up with a one-in-three uptake by patients using it for symptom control. The longitudinal nature of the project showed that those who found benefit from a cannabis product remained on it with a positive effect. Further research needs to disentangle many of the above issues discussed. Distinctions should be made between carboxylated (inactive) and decarboxylated (active) tetrahydrocannabinol (THC) and cannabidiol (CBD) content on product labels. Cannabinoid content reporting should also extend beyond just THC and CBD, as it may shed light on the therapeutic potentials of other cannabinoids. Non-cannabinoid phytochemicals have also shown cannabinoid receptor binding activity although the clinical significance of this is yet to be determined. The task of quantifying cannabinoid intake is further compounded by the challenges of ensuring standardized delivery methods (e.g., smoked vs vaporized formulations). H. Clarke, MD, PhD (&) H. Meng, MD Department of Anesthesiology and Pain Medicine, University of Toronto, Toronto, ON, Canada e-mail: [email protected]