Only sporadic data are available on hair concentrations of diazepam and some of its metabolites (nordazepam, oxazepam, and temazepam) following a single controlled dose. The aim of this study was to investigate the deposition of diazepam and its metabolites in human hair after eight healthy volunteers (four women and four men, ages 24-26, East Asian) consumed 10 mg of diazepam. Hair was collected from all volunteers 1 month after exposure, and also 2 months post-exposure from men and 10 months post-exposure from women. Diazepam and the complete metabolite profile, including oxazepam glucuronide and temazepam glucuronide, were measured by ultra-high pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with limits of quantifications (LOQs) of 0.5-2.5 pg/mg for diazepam, nordazepam, oxazepam, and temazepam, and of 10 pg/mg for oxazepam glucuronide and temazepam glucuronide. There were no differences by gender in the amounts of diazepam or metabolites found. The concentration of the main metabolite nordazepam was consistently higher than that of diazepam at both 1 and 2 months after consumption. Oxazepam and temazepam traces were found in some volunteers' hair, but the glucuronides were not detected. Diazepam and nordazepam levels at 10 months post-exposure were extremely low (near the LOQ), indicating drug loss by personal hygiene and physical handling. To our knowledge, this is the first single-dose diazepam study using black hair and the first study to include measurements of oxazepam glucuronide and temazepam glucuronide in human hair.

A novel and simple online solid-phase extraction liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous determination of diazepam and its five metabolites including nordazepam, oxazepam, temazepam, oxazepam glucuronide, and temazepam glucuronide in human oral fluid. Human oral fluid was obtained using the Salivette(®) collection device, and 100 μL of oral fluid samples were loaded onto HySphere Resin GP cartridge for extraction. Analytes were separated on a Waters Xterra C18 column and quantified by liquid chromatography with tandem mass spectrometry using the multiple reaction monitoring mode. The whole procedure was automatic, and the total run time was 21 min. The limit of detection was in the range of 0.05-0.1 ng/mL for all analytes. The linearity ranged from 0.25 to 250 ng/mL for oxazepam, and 0.1 to 100 ng/mL for the other five analytes. Intraday and interday precision for all analytes was 0.6-12.8 and 1.0-9.2%, respectively. Accuracy ranged from 95.6 to 114.7%. Method recoveries were in the range of 65.1-80.8%. This method was fully automated, simple, and sensitive. Authentic oral fluid samples collected from two volunteers after consuming a single oral dose of 10 mg diazepam were analyzed to demonstrate the applicability of this method.

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