Flunitrazepam

Ensuring analyte stability is essential for accurate forensic and clinical detection of sedative-type drugs. This study systematically evaluated the stability of 22 sedative-type drugs and metabolites in human urine under controlled conditions varying by pH (4.0, 7.0), temperature (25°C, 4°C, −20°C), and freeze–thaw cycles (5 cycles), using a fully validated liquid chromatography–tandem mass spectrometry (LC–MS/MS) method. While compounds such as midazolam, clobazam, and zolpidem remained highly stable, others—including alprazolam, triazolam, and lorazepam—exhibited notable degradation, particularly under acidic pH and elevated temperature. Flunitrazepam and clonazepam showed distinct degradation with the formation of 7-amino metabolites at neutral pH. Notably, this transformation occurred only in urine and not in phosphate-buffered saline, suggesting a urine-specific mechanism. These findings highlight the importance of compound-specific preservation strategies. In scenarios where analyte identity or sample pH cannot be verified promptly, immediate refrigeration or freezing (ideally at −20°C), along with minimizing freeze–thaw cycles, is strongly recommended to preserve sample integrity and ensure reliable toxicological interpretation.

Affinity-based protein profiling (AfBPP) allows us to identify target proteins that bind drugs or other small molecules of interest in complex samples. As an enrichment technique, label-free AfBPP often generates data with high missingness, particularly in negative control samples. We developed an R package, chemoprotR, which enables both quantitative and qualitative statistical analyses of chemoproteomic data, and applied it to the identification of specific benzodiazepine drug targets in the brain. Benzodiazepines comprise a class of drugs that affect GABA_A receptors through positive allosteric modulation, but benzodiazepine interactions with other proteins are not fully understood. To this end, we synthesized benzodiazepine affinity-based probes (AfBPs) and applied them to rat brain synaptosomes. Our benzodiazepine AfBPs identified GABA_A receptor subunits and other proteins with ion channel functions. Across the three probes, there was minimal overlap in protein targets identified by competitive labeling with flurazepam, and FR-DA, the probe based on flurazepam, yielded more significant protein targets than the probes based on flunitrazepam. These results demonstrate the ability of benzodiazepine AfBPs to identify protein targets when used with an authentic benzodiazepine to compete for binding sites and highlight the utility of combined statistical analyses for the interpretation of presence-absence data in AfBPP data sets.