New Biomarker Improves Detection of Knockout Drops
When the use of knockout drops is suspected, every hour counts. GHB, a substance frequently used for this purpose, disappears quickly from the blood and urine. Researchers at the University of Zurich have now investigated a new biomarker using forensic urine samples. This biomarker can provide evidence of prior use, even when GHB is no longer detectable using conventional methods.
Gamma-hydroxybutyric acid (GHB) can be consumed as a recreational drug or secretly administered as a “knockout drug,” for example, to render a victim unconscious. Among other effects, it can cause impaired consciousness and memory lapses. Detecting it is difficult in forensic medicine: In blood, the typical detection window is about six hours; in urine, it is about twelve hours. In addition, GHB occurs naturally in the body in small amounts and can also form after death.
Promising Discovery
As early as 2021, a research team led by Andrea Steuer from the Institute of Forensic Medicine at the University of Zurich, in collaboration with the University Psychiatric Hospital Zurich, discovered a promising biomarker. It is a compound of GHB and a sugar, presumably ribose (GHB-pentose). The exact chemical structure has not yet been definitively determined. Unlike GHB itself, this biomarker remains detectable in urine for a longer period after ingestion.
Subsequent controlled studies examined the biomarker’s potential in greater detail. A study published in 2025 showed that GHB-pentose can remain detectable in urine for up to three days after GHB ingestion. However, it remained unclear whether these findings would be confirmed under the varying conditions of forensic practice.
First Reliable Practical Results
For the recently published study, the team analyzed 2,414 anonymized urine samples from forensic cases dating from 2024 to 2026 using two independent mass spectrometric analytical methods. GHB-pentose was also detected in all 21 GHB-positive urine samples from living individuals.
Fourteen additional samples were particularly revealing: although the measured GHB levels were below the threshold set for the analysis, GHB-pentose was detected. In eight of these 14 cases, the case information supported the suspicion of prior GHB ingestion or administration. Among these were three suspected criminal cases—two robberies and one alleged sexual assault—in which the urine samples were not collected until 13 to 16 hours after the incident. “These results thus provide the first evidence from forensic practice that GHB-pentose remains detectable beyond the usual detection window for GHB,” says last author Andrea Steuer.
Detecting GHB Use Before Death
GHB can also form in the body after death. Therefore, when the substance is detected in deceased individuals, it is not always clear whether it was ingested beforehand. Unlike GHB itself, GHB-pentose appears to form only after the substance has been ingested. In 20 urine samples from deceased individuals that were analyzed, the researchers found elevated GHB levels but no GHB-pentose. In four other samples, however, both substances were detectable. “The biomarker could therefore also aid in the investigation of deaths in the future,” says Steuer. However, further research is needed for this.
Already applicable in forensic practice
The researchers also demonstrated that GHB-pentose can be detected using two different measurement methods commonly used in forensic toxicology. This makes it possible to integrate the test into existing laboratory procedures, even though no commercially available reference standard currently exists. “When we suspect that knockout drops have been administered, we now routinely test for GHB-pentose as well,” notes Steuer.
The results are promising but do not yet allow for a definitive conclusion regarding diagnostic reliability or the maximum detection window in individual cases. Therefore, the joint evaluation of laboratory findings and case circumstances remains crucial.
Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.
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