The enactment of marijuana legalization in Canada preceded a “marked decline” in the volume of opioids prescribed to patients enrolled in both public and private health care plans, according to data published in the journal Applied Health Economics and Health Policy.

A team on investigators affiliated with the University of Toronto assessed the volume of opioids prescribed, and the amount of money spent on opioids, in the months immediately preceding and immediately following the legalization of adult-use marijuana sales. Researchers obtained claims data for more than 80 percent of all of the opioids prescribed in Canada during the study period (January 2016 to June 2019).

Consistent with the findings of other ecological studies, researchers determined, “The legalization of cannabis coincided with a marked drop in opioid volumes prescribed in Canada.”

Authors concluded: “The findings of this 42-month time-series analysis revealed a steady and significantly consistent decline in the mean and median MED [morphine equivalent dose] per claim for public payer drug plans. However, when comparing the pre- versus post-legalization time periods, the decline in the mean MED per claim was approximately 5.4 times greater in the period following legalization (22.3 vs. 4.1 mg per claim). In addition, total public payer monthly opioid spending reductions averaged $Can95,000 per month before October 2018 [when adult-use sales were legalized] compared to $Can267,000 per month following the legalization of cannabis. Similar findings were also observed within private drug plans. … The findings of this study add to the growing body of evidence that easier access to cannabis for patients with pain may reduce opioid use and partially offset expenditures for both public and private drug plans.”

The abstract of the study, “Opioid prescribing in Canada following the legalization of cannabis: A clinical and economic time-series analysis,” appears online here. Additional information is available from the NORML fact-sheet, “Relationship Between Marijuana and Opioids.”