Changing risk and presentation of overdose associated with consumption of street drugs at a supervised injection site in Vancouver, Canada

Abstract

Background: British Columbia is experiencing a public health emergency due to overdoses resulting from consumption of street drugs contaminated with fentanyl. While the risk of overdoses appears to be increasing, the overdose rate and severity of overdose presentations have yet to be quantified.

Methods: Insite is a supervised injection site in Vancouver. Data from Insite's client database from January 2010 to June 2017 were used to calculate overdose rates as well as the proportion of overdoses involving rigidity and naloxone administration over time in order to estimate changes in the risk and severity of overdose resulting from changes in the local drug supply.

Results: The overdose rate increased significantly for all drug categories. Heroin used alone or with other drugs continues to be associated with the highest overdose rate. The overdose rate associated with heroin increased from 2.7/1000 visits to 13/1000 visits over the study period, meaning that clients were 4.8 times more likely to overdose in the most recent period as in the baseline period. The proportion of overdose events involving rigidity, a known complication of intravenous fentanyl use, increased significantly from 10.4% to 18.9%. The proportion of overdoses requiring naloxone administration increased significantly from 48.4% to 57.1% and is now similar across all drug categories.

Conclusions: The risk and severity of overdoses at Insite have increased since the emergence of illicit fentanyl. This information derived from supervised injection site data can be used to inform local harm reduction efforts and the response to the overdose emergency.

Keywords: Addiction; Fentanyl; Insite; Overdose; Supervised injection site; Vancouver.