Welcome to the IME Insider

Timely information and insights into the world of evidence-based medicine as it applies to IMEs and other health-related services across Canada. Your feeback and suggestions are welcome.

Part 2: Dosing, Side Effects and Workplace Considerations


According to Health Canada, “Cannabis is not an approved therapeutic product. ” It further notes that “there is no scientifically defined dose of cannabis for any specific medical condition.” Formally, only synthetic cannabis (Nabilone) and the botanical extract are approved versions of cannabinoids. Dosing requirements of the various forms of cannabis can fluctuate widely according to multiple variables including THC potency, method of ingestion, individual genetics, and past exposure among many other factors. Global studies of patients using cannabis for medical purposes have to date shown dosing of 0.8 to 1.5 g/day of dried cannabis as representative dosing.

Dosing of cannabis remains individualized and should be appropriately titrated to reach the required therapeutic effect. Health Canada suggests that most individuals should use less than three grams daily of dried marijuana, whether taken orally or inhaled, or a combination of both.

Side Effects and Workplace Implications

Use of cannabis has been shown to be associated with potential impairment of cognitive and motor functioning. Specific effects can include impairment in memory and coordination, distortion of time perception, reduced job performance and attendance issues, changes in social functioning, and impairment in judgment. These effects can be present regardless of whether cannabis is being used for recreational purposes or for medical purposes (i.e., use authorized by a health professional). Because cannabis-related impairment can last in excess of 24 hours after use, cannabis use (for either recreational or medical reasons) would be a factor to consider whether an individual is fit to participate in safety sensitive tasks or jobs.

Several body fluids can be tested for the presence of cannabis, but a positive test can only indicate whether the substance has been used, and currently is not considered to be a reliable indication of impairment.

As mentioned in Part 1 of this series, stakeholders should recognize the rapid and continuously evolving nature of this topic and ensure they obtain accurate and updated information from the regulatory and industry bodies, in conjunction with expert medical/legal opinions for additional detail and guidance. The above is intended as a current sampling of some industry policies only and is not intended to guide decision making.

  1. [REF: Canadian Tobacco Alcohol and Drugs (CTADS): 2015 Summary https://www.canada.ca/en/health-canada/services/canadian-tobacco-alcohol-drugs-survey/2015-summary.html]
  2. [REF: HEALTH CANADA http://laws-lois.justice.gc.ca/eng/regulations/SOR-2016-230/index.html]
  3. [REF: CPSO. Marijuana for Medical Purposes. http://www.cpso.on.ca/policies-publications/policy/marijuana-for-medical-purposes]