Background: Fatal overdoses from opioid use and substance disorders are increasing at an alarming rate. One proposed harm reduction strategy for reducing overdose fatalities is to place overdose prevention sites - commonly known as safe injection facilities - in proximity of locations with the highest rates of overdose. As urban centers in the United States are tackling legal hurdles and community skepticism around the introduction and location of these sites, it becomes increasingly important to present compelling evidence of impact and safety.
Methods: We developed a mathematical model to describe the movement of opioid users to an overdose prevention site in order to understand the impact that the facility would have on overdoses, fatalities, and user education and recovery. The discrete-time, stochastic model is able to describe a range of user behaviors, including the effects from how far they need to travel to the site. We calibrated the model to overdose data from Philadelphia, and ran simulations to describe the effect of placing a site in the Kensington neighborhood.
Results: In Philadelphia, which has a non-uniform racial population distribution, choice of site placement can determine which demographic groups are most helped. In our simulations, placement of the site in the Kensington neighborhood resulted in disproportionate benefits for white users. Simulations also predict that direct effects from overdose reversal in the overdose prevention site are small (about 6 fewer fatalities per year per 30 spots at the overdose prevention site without other effects). However, fatalities and nonfatal overdoses are predicted to decrease substantially when indirect effects from site safety and education of users are considered.
Conclusions: Cities and locales can use mathematical modeling to help quantify the predicted impact of placing an opioid prevention site in a particular location. To fully understand the impact of site placement, it is recommended to include both direct and indirect effects in analysis. Introducing more than one site and distributing sites equally across neighborhoods with different racial and demographic characteristics would have the broadest public health impact.