Characterizing rapid changes in the prevalence and concentration of key compounds in Philadelphia’s street opioid retail supply, March 2024-March 2025

Objective

The objective of this observational epidemiological study is to examine recent shifts in the street opioid supply of the largest U.S. open-air drug market, including changes in prevalence and concentration of key compounds.

Methods

From March 2024-March 2025, samples of street drugs sold as opioids were collected at a harm reduction program in Philadelphia’s Kensington neighborhood and shipped to the National Institute of Standards and Technology, where they underwent qualitative testing using direct analysis in real-time mass spectrometry and quantitative testing using liquid chromatography tandem mass spectrometry. Bootstrapped quantile regression models assessed changes in concentration over time.

Results

Among 260 samples, fentanyl (98 %) and xylazine (65 %) were the most prevalent psychoactive compounds. While fentanyl was consistently present, the median fentanyl concentration decreased significantly, from 9.6 % by mass in May 2024–5.3 % by mass in March 2025 (P = 0.020). Xylazine prevalence declined from 100 % in March 2024–58 % in March 2025. Conversely, lidocaine and tetracaine prevalence increased from 3 % each in March 2024–63 % each in March 2025. Two novel compounds, medetomidine and bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (BTMPS), were first detected in April and June 2024, reaching prevalence rates of 83 % and 25 % by March 2025, respectively.

Conclusion

The street opioid supply in Kensington is erratic and volatile, with decreasing fentanyl concentrations alongside increasing adulteration with medetomidine and local anesthetics. These shifts underscore urgency for timely systematic drug checking and robust inquiry into the organization of street opioid retail markets to inform harm reduction strategies and prevent drug-related harms.