PROJECT ABSTRACT Fentanyl contamination of heroin and other drugs is increasingly common, leading to significant rates of unintentional fentanyl-related overdoses. Fentanyl test strips (FTS) are a low-threshold approach to mitigating fentanyl-related overdose risk among people who use drugs (PWUD). Using FTS, PWUD can dissolve a small quantity of a drug into water to test for the presence of fentanyl. PWUD report that FTS are easy to use with few logistical and environmental barriers associated with use. Moreover, emerging evidence indicates that FTS use positively impacts subsequent actions. In prior work conducted by our team, PWUD in Philadelphia reported exceptionally high rates of positive FTS results on non-heroin drugs, far higher than rates seen in other locations. Possible explanations for these discordant results include saturation of the Philadelphia illicit drug market with fentanyl, incorrect use of FTS, incorrect interpretation of FTS, or a combination of the three. Despite increasing distribution of FTS, no studies to date have explored the accuracy of FTS use by PWUD. In addition, while the prevalence of fentanyl in the heroin supply has been widely documented, it is currently unknown to what extent fentanyl is present in non-heroin drug markets. Based upon the recent findings in Philadelphia reporting alarmingly high rates of FTS positivity with non-heroin drugs and these gaps in current knowledge regarding both FTS use and contamination of the non-heroin drug supply, there is an urgent need to assess the accuracy of FTS use among PWUD and the extent fentanyl is present in the Philadelphia non- heroin drug supply. The long-term goal of this work is to advance overdose prevention measures using FTS and other drug-checking technology in drug markets around the U.S. The overall objective of this proposal is to leverage established municipal and community partnerships in Philadelphia and the use of advanced drug- checking technology to explicate gaps identified between previously detected levels of fentanyl in the drug supply and self-reported results from FTS use among PWUD in Philadelphia. Our objective will be achieved with two specific aims: (1) Determine user process of use and interpretation of FTS and (2) Estimate the true presence of fentanyl in the non-heroin drug supply in Philadelphia, PA. This study will have significant impact by addressing knowledge gaps regarding utility of FTS as a harm reduction strategy and providing actionable evidence regarding the extent of fentanyl presence in non-heroin drugs. We anticipate three outcomes from aims: (1) the identification of educational gaps in the proper use of FTS and interpretation of their results among PWUD, (2) point-in-time data for fentanyl contamination of non-heroin illicit drugs in Philadelphia, and (3) informing ongoing national campaigns to educate PWUD about FTS and overdose prevention strategies. Study findings will enhance evidence-based overdose prevention efforts targeted at supply-side fentanyl contamination and real-world FTS use practices by PWUD.

PROJECT NARRATIVE Fentanyl test strips (FTS) are increasingly being used by people who use drugs, including those who use drugs other than heroin, to detect the presence of fentanyl in the unregulated drug supply as a strategy to prevent unintentional fentanyl overdose. Recent work based in Philadelphia found alarmingly high rates of FTS positivity in non-heroin drugs, suggesting that people who use drugs are incorrectly using FTS, incorrectly interpreting results, the non-heroin drug supply is much more contaminated than prior estimates have suggested, or a combination of the three. This project will fill important evidence gaps by assessing the real- world accuracy of FTS use by people who use drugs and current presence of fentanyl in non-heroin drugs in Philadelphia, Pennsylvania.