title: Cannabis for the Management of Pain: Assessment of Safety Study (COMPASS).
abstract: Cannabis is widely used as a self-management strategy by patients with a wide range of symptoms and diseases including chronic non-cancer pain. The safety of cannabis use for medical purposes has not been systematically evaluated. We conducted a prospective cohort study to describe safety issues among individuals with chronic non-cancer pain. A standardized herbal cannabis product (12.5% tetrahydrocannabinol) was dispensed to eligible individuals for a 1-year period; controls were individuals with chronic pain from the same clinics who were not cannabis users. The primary outcome consisted of serious adverse events and non-serious adverse events. Secondary safety outcomes included pulmonary and neurocognitive function and standard hematology, biochemistry, renal, liver, and endocrine function. Secondary efficacy parameters included pain and other symptoms, mood, and quality of life. Two hundred and fifteen individuals with chronic pain were recruited to the cannabis group (141 current users and 58 ex-users) and 216 controls (chronic pain but no current cannabis use) from 7 clinics across Canada. The median daily cannabis dose was 2.5 g/d. There was no difference in risk of serious adverse events (adjusted incidence rate ratio = 1.08, 95% confidence interval = .57-2.04) between groups. Medical cannabis users were at increased risk of non-serious adverse events (adjusted incidence rate ratio = 1.73, 95% confidence interval = 1.41-2.13); most were mild to moderate. There were no differences in secondary safety assessments. Quality-controlled herbal cannabis, when used by patients with experience of cannabis use as part of a monitored treatment program over 1 year, appears to have a reasonable safety profile. Longer-term monitoring for functional outcomes is needed.
  
  
  BACKGROUND
  The study was registered with www.controlled-trials.com (ISRCTN19449752).
  
  
  CONCLUSIONS
  This study evaluated the safety of cannabis use by patients with chronic pain over 1 year. The study found that there was a higher rate of adverse events among cannabis users compared with controls but not for serious adverse events at an average dose of 2.5 g herbal cannabis per day.
authors.affiliation: Department of Anesthesia, McGill University, Montreal, Quebec, Canada; Department of Family Medicine, McGill University, Montreal, Quebec, Canada. Electronic address: mark.ware@mcgill.ca.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ware
authors.affiliation: Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada.
authors.forename: Tongtong
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada; Centre for Clinical Epidemiology, Jewish General Hospital, Montreal, Quebec, Canada.
authors.forename: Stan
authors.initials: S
authors.lastname: Shapiro
authors.affiliation: Department of Pediatrics, University of British Columbia; Child and Family Research Institute, Vancouver, British Columbia, Canada.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Collet
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002170:Canada; D059350:Chronic Pain / Q000188:drug therapy*; D003071:Cognition / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000009:adverse effects* / Q000592:standards / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D020714:Maximum Tolerated Dose; D064086:Medical Marijuana / Q000009:adverse effects* / Q000592:standards / Q000627:therapeutic use; D008875:Middle Aged; D059408:Pain Management / Q000009:adverse effects / Q000379:methods; D011446:Prospective Studies; D011786:Quality Control; D011788:Quality of Life; D055815:Young Adult
chemical_list: D064086:Medical Marijuana; D013759:Dronabinol
keywords: Cannabis; adverse events; chronic pain; cohort study; safety