(B-128) Medical Cannabis Use in Association with Drugs Associated with Risks of Interaction with Cannabinoids: A Longitudinal Cohort Study

Monday, August 25, 2025

11:30 AM - 1:00 PM ET

Presenting Author(s)

Zoumana Cheick Bérété, MD

Faculty of Pharmacy, Université Laval, Quebec City, Quebec, Canada

Co-Author(s)

AS

Arvis Abraham Sebgo

Faculty of Pharmacy, Université Laval, Quebec City, Quebec, Canada
DE

Dean Eurich

School of Public Health, University of Alberta, Edmonton, Alberta, Canada., Alberta, Canada
JH

John G. Hanlon

Department of Anesthesiology and Pain Medicine, University of Toronto, Ontario, Canada.
Toronto, Ontario, Canada
JD

Jason Dyck

Cardiovascular Research Centre, Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
Edmonton, Alberta, Canada
CL

Cerina Lee

Department of Mental Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States
Baltimore, Maryland, United States
AZ

Arsène Zongo

Population Health and Optimal Health Practices Research Axis, CHU de Québec - Université Laval Research Centre, Quebec City, Quebec, Canada
Québec, Quebec, Canada

Background: Cannabinoids interact with multiple drugs with some interactions having significant clinical effects. The worldwide increasing use of cannabis for medical care potentially expose patients, particularly older patients, to adverse drug reactions. .

Objectives: This study aimed to evaluate among the elderly 1) the trends in the concomitant use of cannabis and drugs associated with a risk of significant clinical interaction with cannabinoids (DARSCIC) including those with a narrow therapeutic index (DNTI) such as warfarin, and 2) the risk of warfarin-related bleeding and drug-related intoxication.

Methods: For objective 1, we conducted an interrupted time series study among12599 seniors who received an authorized cannabis prescription in Ontario from 2014-2019, and 48651 controls. Using clinical and medico-administrative data, dispensations of DARSCIC were assessed pre-post cannabis prescription. For objective 2, longitudinal cohorts studies were conducted in patients concomitantly exposed to cannabis and warfarin (bleeding) or to DNTI (intoxication) versus controls exposed to warfarin or DNTI only.

Results: For objective 1, the trends of DARSCIC/DNTI dispensations were similar in the year before and after cannabis prescription. For objective 2, among 378 patients exposed to cannabis and warfarin, the risk of bleeding was 1.19, 95%CI (0.71-1.98), compared to 1646 controls. The risk of drug-related intoxication was 3.24, 95%CI (1.70-6.15) among 3917 patients exposed to cannabis and DNTI compared to 12213 controls.

Conclusion: The results suggest that the prescription of cannabis does not account for DARSCIC/DNTI. This possible lack of DARSCIC knowledge among cannabis prescribers may expose patients to high risk of intoxication and potentially bleeding.

Key words: medical cannabis; cannabinoids; drug interaction; time series analysis; bleeding, intoxication, older patients