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Related Concept Videos

Urine Studies I: Urinalysis01:29

Urine Studies I: Urinalysis

Urinalysis is a widely used diagnostic test that analyzes urine's physical, chemical, and microscopic characteristics. Healthcare providers use it to detect and monitor various health conditions, including renal disease, urinary tract infections (UTIs), diabetes, and metabolic or systemic disorders.Components of UrinalysisUrinalysis consists of three primary components: physical, chemical, and microscopic examination. Each provides unique insights into the urine sample and, by extension, the...
Serum Studies: Renal Function Tests01:24

Serum Studies: Renal Function Tests

Renal function tests are crucial for assessing kidney health, monitoring disease progression, and evaluating the kidneys' efficiency in waste elimination, fluid balance, and electrolyte regulation. These tests offer critical insights into kidney function, even though routine measurements may appear normal until there is a significant decline in the glomerular filtration rate or GFR. Typically, signs of kidney impairment only become evident when the GFR falls to about 50% of its normal level.
Drug Concentrations: Measurements01:23

Drug Concentrations: Measurements

Drug concentration is the quantity of a drug present in a biological sample. Measuring drug amounts in biological samples allows the clinician to understand how a drug is absorbed, distributed, metabolized, and excreted. Samples can be obtained through invasive or non-invasive methods. Invasive techniques involve surgical or parenteral interventions to gather blood, cerebrospinal fluid, or tissue biopsy. Conversely, non-invasive approaches provide samples like urine, feces, and saliva.
Plasma —...
Urine: Physical and Chemical Properties01:18

Urine: Physical and Chemical Properties

Urine comprises approximately 95% water and 5% solutes. The primary ingredient, apart from water, is urea - a byproduct of the breakdown of amino acids. Other notable components include uric acid, a residue from nucleic acid metabolism, and creatinine, a metabolite from creatine phosphate breakdown in skeletal muscle tissue.
The concentration of these solutes varies, with urea being the most abundant nitrogenous waste product. Other solutes include sodium, chloride, potassium, phosphate,...

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Updated: Jun 25, 2026

Gas Chromatography-Mass Spectrometry Paired with Total Vaporization Solid-Phase Microextraction as a Forensic Tool
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What constitutes a normal ante-mortem urine GHB concentration?

Francesco Mari1, Lucia Politi, Claudia Trignano

  • 1Forensic Toxicology Division, Department of Anatomy, Histology and Legal Medicine, University of Florence, Italy. francesco.mari@unifi.it

Journal of Forensic and Legal Medicine
|February 26, 2009
PubMed
Summary

Gamma-hydroxybutyric acid (GHB) is a medication and controlled substance. Current urinary GHB cut-offs require caution, as therapeutic use can yield concentrations near established limits, complicating forensic analysis.

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Published on: March 1, 2018

Area of Science:

  • Forensic Toxicology
  • Pharmacology
  • Neuroscience

Background:

  • Gamma-hydroxybutyric acid (GHB) is an endogenous substance and a prescribed medication (Zyrem/Alcover).
  • GHB is a controlled substance with a narrow safety margin, posing challenges in forensic interpretation.
  • Post-mortem GHB concentrations are difficult to interpret due to endogenous production and post-mortem artifactual increases.

Purpose of the Study:

  • To investigate urinary GHB concentrations in patients undergoing therapeutic treatment.
  • To evaluate the existing forensic cut-off levels for GHB in urine.
  • To determine if therapeutic GHB use interferes with the forensic identification of drug-facilitated assault.

Main Methods:

  • Analysis of urinary GHB concentrations in three groups: GHB-treated alcoholics (n=39), healthy volunteers (n=30), and alcoholics pre-GHB treatment (n=30).
  • Comparison of GHB levels between therapeutic users and non-users.
  • Assessment of urinary GHB concentrations relative to established forensic cut-off values.

Main Results:

  • Over one-third (36.6%) of patients treated with GHB exhibited urinary concentrations between 2.75 and 10 microg/mL.
  • Significant overlap exists between therapeutic GHB levels and potential forensic thresholds.
  • Endogenous GHB production and post-mortem changes complicate interpretation.

Conclusions:

  • Caution is advised when interpreting urinary GHB concentrations, particularly when using a cut-off of 10 microg/mL.
  • Therapeutic GHB use can produce levels that challenge forensic interpretation, necessitating careful case evaluation.
  • Forensically defensible cut-offs for post-mortem GHB require further investigation and are unlikely to be definitively established.