Biomarker extends the detection window for knockout drops
Keystone-SDA
With a new biomarker, knockout drops can be detected for longer than before. They remain detectable even after the active ingredient itself has already been broken down, according to the University of Zurich (UZH).
If the use of knockout drops is suspected, every hour counts, the UZH said in a press release issued on Tuesday.
A substance frequently used as a ‘knock-out’ drug is gamma-hydroxybutyrate (GHB). GHB is consumed as a recreational drug or secretly administered to render people unconscious. It can cause disturbances of consciousness and memory lapses. It is usually detectable in the blood for only around six hours and in the urine for around 12 hours. After that, ingestion can often no longer be detected on the basis of the active substance.
When GHB is ingested, the substance binds with a sugar to form what is known as GHB-pentose. Researchers use this as a biomarker – that is, a biological indicator of previous GHB consumption. Initial evidence of this marker was discovered as early as 2021 by a team led by Andrea Steuer at the Zurich Institute of Forensic Medicine.
Longer detection time in practice
The experts have now used this method to analyse 2,414 anonymised urine samples from 2024 to 2026.
The method proved reliable in several suspected cases of criminal offences: even 13 to 16 hours after two robberies and an alleged sexual assault, the experts were able to detect the substance, even though the levels of GHB had already fallen below the detection limit. The results were published in the specialist journal Drug Testing and Analysis.
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The method also opens up new possibilities in cases of unexplained deaths. GHB is sometimes produced naturally in the body after death. According to the study’s findings, however, GHB-pentose only forms if the substance was ingested while the person was still alive. The researchers detected GHB in 20 urine samples from deceased individuals, but not the pentose compound. This suggests that the deceased had not ingested GHB while alive.
The Institute of Forensic Medicine at the University of Zurich has already integrated the analysis into its regular laboratory procedures, the university announced. However, it said further investigations were needed to draw definitive conclusions regarding the maximum detection period in individual cases.
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Translated from German, reviewed by an English Department journalist.
