Multi-drug involvement in apparent opioid and stimulant toxicity deaths in Canada from 2018 to 2023: Summary

Highlights

• There was a clear shift in substances and substance combinations involved in opioid- and stimulant-related toxicity deaths between 2018 and 2023 in Canada. The percentage of toxicity deaths involving multi-drug combinations of 3 or more substances doubled between 2018 (20%) and 2023 (42%).
• Patterns of substance group combinations were similar between sexes, despite males accounting for nearly three-quarters of substance-related deaths in Canada. By 2023, opioids with stimulants with or without other psychoactive substances accounted for almost 60% of deaths in both sexes. Deaths involving opioids alone dropped to 10%.
• Toxicity deaths involving multi-drug combinations of opioids with stimulants and other psychoactive substances were present in all age groups but were less frequent in those over 50 years of age, while opioids alone and stimulants alone were most frequent in the oldest age group (60+ years of age).
• Substances involved in opioid and stimulant-related deaths varied by region in Canada. While deaths involving opioids with stimulants and other psychoactive substances were found in all regions of the country, deaths involving opioids with other psychoactive substances were more frequent in eastern Canada.
• Identifying the combinations of substances and substance groups most frequently involved in substance-related toxicity deaths is necessary for informing evidence-based programs and policies aimed at preventing deaths in the dynamically changing crisis. Understanding regional and demographic dynamics is important for tailoring prevention and intervention strategies, ultimately helping to mitigate the impact of multi-drug toxicity.

Background

For over a decade, Canada has experienced an unrelenting crisis of premature deaths related to the toxic, unregulated drug supply. Data on drug seizure samples from the Drug Analysis Service (DAS) highlight the increasing complexity of the illegal drug supply in Canada. Analyzed samples contain unexpected mixtures, including both well-known and newly emerging drugs ^{Reference 1} .

Over the last few years, opioids and stimulants sold in the unregulated drug market have increasingly contained other substances such as:

• benzodiazepines, which cause sedation
• ultra-potent opioids (e.g. nitazines), which cause respiratory depression

Their combinations complicate clinical presentations and contribute to increased risk of dependence and death ^{Reference 2Reference 3Reference 4}.

Multi-drug toxicity occurs when the combined effects of more than one substance leads to a drug-related death. This has become increasingly common in Canada during the last few years. Due to the evolving multi-drug nature of the crisis, further analysis is needed. Data helps us understand the complex interplay between shifting substance use patterns and demographics and their impact on toxicity deaths.

Research objectives

This study provides insights on the substances involved in multi-drug toxicity deaths. We analyzed data from up to 10 provinces and territories (P/Ts) between 2018 and 2023 to:

1. Describe the specific substances and substance groups involved in apparent opioid or stimulant toxicity deaths, where multiple substances or substance groups from the opioid, stimulant and/or other psychoactive categories were present
2. Examine shifts in patterns and trends of substance combinations in opioid and stimulant deaths, including changes in the substances or substance groups, by year, region, sex, and age

Discussion

Although our analysis did not include data from British Columbia, Alberta, and Manitoba (which account for approximately 50% of opioid- and stimulant-related toxicity deaths in Canada), these findings are consistent with previous Canadian studies ^{Reference 5 Reference 6 Reference 7 Reference 8 Reference 9 Reference 10 Reference 11 Reference 12}, which have shown similar trends of increased frequency of multi-drug combinations in those provinces ^{Reference 10}.

While this study focuses on postmortem toxicology findings, data from drug checking services and drug seizures also report an increase in the presence of multi-substance mixtures in the unregulated supply—such as multiple opioids, opioids with benzodiazepines, and stimulant-opioid mixtures—that align with the patterns observed in toxicity deaths ^{Reference 1Reference 13Reference 14}.

Many substances in single drug samples are often unexpected, and those who use stimulants may not anticipate the presence of opioids in their drugs, or may be opioid-naïve, resulting in a higher risk of overdose due to lower tolerance ^{Reference 16}.

Other studies have noted sex-related differences in substance combinations, such as opioids with alcohol or cocaine in males versus opioids with depressants or methamphetamine in females ^{Reference 8 Reference 10}. Our analysis was limited to 6–10 P/Ts, and pre-defined categories of substances, which may have restricted our ability to detect more nuanced sex-related variations in specific substance combinations.

These trends align with previous research ^{Reference 5 Reference 17 Reference 18} and may be influenced by differences in access to and motivations behind substance use ^{Reference 19 Reference 20}. Perspectives from PWLLE confirmed that the drug markets vary across the country and their experience of available substances were in line with the regional differences observed in this report. Furthermore, they highlighted that intentional mixing of substances may be impacted by local substance availability.

This emphasizes the role of local factors—such as drug markets, substance availability, and regional socio-economic conditions—in influencing multi-drug toxicity and the need to assess all regions of Canada separately to accurately characterize and mitigate substance toxicity harms across the country.

References

Acknowledgements

We recognize that the data used in this report may represent stories of pain, grief and trauma. This report cannot adequately reflect the burden borne by people in Canada. We acknowledge all those impacted by substance use and those who work to save lives and reduce substance-related harms on individuals and communities.

We also express our gratitude to our partners and collaborators who provided the data on toxicity deaths and insights on the findings. This includes the provincial and territorial offices of chief coroners and chief medical examiners, provincial and territorial public health and health care partners, and persons with lived and living experience. Additionally, we extend our thanks to all reviewers for their valuable contributions to the report and constructive feedback.

Suggested citation

Multi-Drug Involvement in Apparent Opioid and Stimulant Toxicity Deaths in Canada. Public Health Agency of Canada, Health Infobase.