Study: U.S. fentanyl increasingly mixed with multiple sedatives and industrial chemicals

A new national study from the National Institute of Standards and Technology found that substances mixed into illicit fentanyl vary by region, rise and fall over time, and are becoming more numerous within individual samples — a shifting chemical landscape that could help first responders and public-health officials adapt care more quickly.

The peer-reviewed study offers one of the broadest looks yet at fentanyl adulteration across the United States. For emergency workers and health agencies, the significance is practical: faster, more localized information about what is turning up alongside fentanyl can help guide overdose response, treatment and warnings to clinicians and community programs.

NIST issued a press release on Thursday summarizing the findings. The study, led by NIST researchers including Edward Sisco, was published online Wednesday in Drug Testing & Analysis under the title “Trends in Fentanyl Adulteration From Rapid Drug Analysis and Research (RaDAR) Drug Checking Samples, January 2024 to June 2026.”

Researchers analyzed 4,563 fentanyl-related drug-residue samples collected nationwide from January 2024 through June 2026 through NIST’s Rapid Drug Analysis and Research, or RaDAR, program. RaDAR, launched as a pilot in 2021, is designed to provide near-real-time information on drug composition to public-health, forensic and law-enforcement partners.

The samples were screened using Direct Analysis in Real Time mass spectrometry, or DART-MS, a rapid testing method that NIST says can detect trace compounds in seconds. NIST described the work as surveillance that can reveal changing patterns in the illicit drug supply.

Among the clearest findings was a rise in chemical complexity. NIST said the number of different additives found in a fentanyl sample increased from about one to two in early 2024 to six or more being common by mid-2026.

The study also found clear regional differences, particularly between the East Coast and West Coast. According to NIST, West Coast samples tended to contain fewer different additives, but at higher concentrations, than samples from the East Coast.

Several recurring adulterants stood out. Xylazine, a veterinary sedative that has been linked to severe wound complications, was more common on the East Coast than on the West. Medetomidine, another veterinary sedative, is increasing in the drug supply and in some places appears to be replacing xylazine. NIST said medetomidine is much more potent and can cause severe withdrawal effects.

The study also highlighted BTMPS — bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate — an industrial UV stabilizer used in plastics. NIST said it first appeared in the fentanyl supply in summer 2024 and has since been detected in samples from both the eastern and western United States. The agency described the substance as potentially toxic, including possible eye irritation and burning.

Many of these additives are not opioids. That matters in an overdose response, because naloxone remains essential in suspected opioid overdoses but does not reverse the non-opioid sedative effects of substances such as xylazine or medetomidine. Those additional sedatives can complicate triage and treatment even when fentanyl is also present.

NIST said the broader, 2 1/2-year, multi-region view is a key advance over its earlier regional analyses. Because RaDAR is an ongoing monitoring system rather than a one-time project, the agency said it can spot new local changes quickly.

“RaDAR enables NIST to immediately alert public health officials to the presence of new adulterants in their area, so that they can plan a more effective treatment for people who have consumed fentanyl,” Sisco said.

NIST also said it is tracking how some additives appear to move geographically over time. “We are now tracking fentanyl additives over a wide geographic area, so we can see the movement of some of these additives over time, for example, from Philadelphia, down to Delaware and Maryland, and then out west,” Sisco said.