Large decrease in syringe distribution following the introduction of fentanyl in King County, Washington.

Background: Syringe services programs (SSPs) serve as key platforms to deliver harm reduction services to people who use drugs (PWUD). Changes in drug supply and drug consumption behaviors, particularly the increasing use of fentanyl through non-injection methods, may impact SSP utilization. Material and Methods: We collected routine program data from three SSPs in King County, Washington. Trends in the annual number of syringes distributed and client encounters were assessed using joinpoint regression analysis to determine when statistically significant changes in trends in annual totals occurred and annual percent change (APC) during each period. Results: The number of syringes distributed per year through King County SSPs reached a maximum of 8,733,413 in 2020 and then decreased sharply to 2,482,056 by 2023. Annual syringe distribution totals were stable or increasing during all periods from 1989 to 2020 (APC range: 2.0-35.3 %), and only developed a decreasing trend between 2020 and 2023 (APC=-32.8 %). Total number of SSP client encounters per year was stable between 2010 and 2023 (APC=0.7 %), but an increasing trend in encounters was identified starting in 2008 (APC=4.4 %) at a community-based SSP that distributed safer smoking supplies (pipes). Discussion: A precipitous decline in syringe distribution through King County SSPs began in 2020 and continued through 2023, which coincided with increasing availability of fentanyl in the local drug market. Nevertheless, the trends in client encounters highlight that PWUD continued to seek harm reduction services, with preliminary evidence that distribution of safer smoking supplies may increase the number of client visits.