NIST Study Maps Regional Changes in Fentanyl Adulterants Across the United States

A study by the US National Institute of Standards and Technology (NIST) has documented how the chemical composition of illicit fentanyl varies by region and changes over time, highlighting the value of rapid chemical analysis in forensic investigations.

Published online on 7 October 2026 in Drug Testing and Analysis, the research examined 4,563 qualitative results and 1,224 quantitative results from drug-checking samples collected across 17 US states between January 2024 and June 2026. The samples were analysed through NIST’s Rapid Drug Analysis and Research (RaDAR) programme.

Researchers found that fentanyl samples became increasingly complex, with six or more compounds appearing more frequently in later samples. The study also identified regional differences: samples from the western United States generally contained fewer adulterants but had higher fentanyl concentrations than samples from the eastern United States.

The findings documented changing patterns in substances mixed with fentanyl, including a shift from the veterinary sedative xylazine toward medetomidine in some areas. Researchers also detected BTMPS, an industrial chemical used in plastic manufacturing, in samples from both regions.

Forensic analysis relied on Direct Analysis in Real Time Mass Spectrometry (DART-MS), a technique capable of identifying chemical components in a sample within seconds. Unlike conventional workflows that may require longer preparation and analysis, this approach can help laboratories rapidly identify emerging substances.

The research has implications for forensic toxicology, drug surveillance and death investigations. Identifying adulterants may help investigators interpret toxicology findings, while timely information can support public-health responses to changing drug supplies.

However, the findings describe samples submitted to the RaDAR programme and should not be treated as a complete representation of every illicit drug sample circulating in the United States.