The Fentalog Study: A Subset of Nonfatal Suspected Opioid-Involved Overdoses with Toxicology Testing

samples tested between … and …
of samples tested contained fentanyl, either alone or with other substances.
of samples contained ONLY fentanyl, with no other substances.

Percent of Samples Testing Positive for Selected Drug Classes

In study sites, blood specimens from patients who experienced a suspected opioid-involved overdose tested positive for fentanyl and fentanyl analogs (78%) of the time, more often than any other drug class.

Percent of Samples Testing Positive for Specific Drugs, grouped by Drug Class

Select a drug class to see which specific drugs in that class were most commonly found.

Percent of Samples Testing Positive for Selected Drug Combinations§

In study sites, most blood samples tested positive for multiple substances*. Select “Common Two Substance Combinations” or “Common Three Substance Combinations” to see the substances found in combination most often.

Number of Adulterants per Sample Testing Positive for Fentanyl

In study sites, blood specimens from patients with a suspected opioid-involved overdose that tested positive for fentanyl often tested positive for adulterants. These substances, combined with other illicit or prescription substances, can be harmful.


*The term “substances” refers to drugs, adulterants, and contaminants.

Each sample can test positive for multiple drug classes and for multiple specific drugs.

§A single sample can be counted in multiple combinations. Additionally, other substances are potentially present alongside the listed combinations.

Adulterants are additives that increase the bulk-volume of the combined substances, or are physical, chemical, biological, or other substances that are chemically created in a lab with intent to “mimic” (or have similar effects of) another drug, such as marijuana, cocaine, or morphine. Examples of adulterants include xylazine, diphenhydramine, levamisole, and quinine.  Adulterants can be harmful.

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