What impact did the COVID-19 pandemic have on the variability of fentanyl concentrations in the Vancouver, Canada illicit drug supply? An interrupted time-series analysis

Background Increases in fatal overdoses were observed coinciding with the COVID-19 pandemic across the USA and Canada. Hypothesised explanations include pandemic-attributable healthcare service disruption, social isolation and illicit drug market disruption. Using data from a community drug checking service, this study sought to evaluate how COVID-19 pandemic measures affected the variability in fentanyl concentrations within the local illicit drug market.Methods Using a validated quantification model for fentanyl, Fourier-transform infrared spectra from fentanyl-positive drug checking samples in Vancouver, Canada were analysed to determine fentanyl concentration. An interrupted time-series analysis using an ordinary least squares model with autoregressive adjusted SEs was conducted to measure how the variance in monthly fentanyl concentrations changed following the declaration of the COVID-19 public health emergency in March 2020.Results Over the study period, 4713 fentanyl-positive samples were available for analysis. Monthly variance of fentanyl concentrations ranged from 7.9% in December 2017 to 159.2% in September 2020. An interrupted time-series analysis of variance in fentanyl concentrations increased significantly following the declaration of the COVID-19 public health emergency, with an immediate level change of 26.1 (95% CI 7.2 to 45.0, p=0.011) and a slope change of 15.8 (95% CI 10.2 to 21.4, p