Identification of post-mortem product of zolpidem degradation by hemoglobin via the Fenton reaction.

Zolpidem, N,N-dimethyl-2-[6-methyl-2-(4-methylphenyl)imidazo[1,2-a]pyridin-3-yl]acetamide, is a hypnotic agent widely used in clinical practice but is detected in many clinical cases of fatal intoxication and suicide. In forensic toxicology, the precise determination of zolpidem concentration in blood is a must to provide concrete evidence of death by zolpidem poisoning. However, the concentrations of zolpidem in blood at autopsy often differ from those at the estimated time of death. In the present study, we found that zolpidem was degraded by hemoglobin (Hb) via the Fenton reaction at various temperatures. The mechanism underlying zolpidem degradation involved the oxidation of its linker moiety. The MS and MS/MS spectra obtained by liquid chromatography quadrupole-Orbitrap mass spectrometry (LC-Q-Orbitrap-MS) showed the formation of 2-hydroxy-N,N-dimethyl-2-(6-methyl-2-(p-tolyl)imidazo[1,2-a]pyridin-3-yl)acetamide (2-OH ZOL) in Hb/H2O2 solution incubated with zolpidem and in the blood of several individuals who died from ingestion of zolpidem. These results suggest that 2-OH ZOL is the post-mortem product of zolpidem degradation by Hb via the Fenton reaction.

Presence of Hypnotics in the Cord Blood and Breast Milk, with No Adverse Effects in the Infant: A Case Report.

Background: Hypnotics are frequently used for insomnia in pregnant and lactating women. This case study assessed zolpidem concentrations in the cord blood and breast milk and ramelteon concentrations in the breast milk of a woman who was treated with zolpidem and ramelteon for insomnia. Materials and Methods: Zolpidem concentrations were measured in maternal serum, breast milk, and cord blood. Concentrations of ramelteon and M-II, an active ramelteon metabolite, were measured in maternal serum and breast milk. Case Report: A 46-year-old female patient diagnosed with insomnia received 5-10 mg/day zolpidem during pregnancy and lactation and 8 mg/day ramelteon during lactation. A male infant weighing 3,329 g was born at 38 weeks' gestation, with no congenital abnormalities found during pregnancy or at birth. The infant was normal at the 1-month postpartum checkup. The maternal/placental ratio of zolpidem concentrations was 0.1 at 7.4 hours after maternal dosing, similar to that reported in previous studies. The calculated relative infant dose through breast milk based on the maximum drug concentration in breast milk at 2.2 hours after maternal dosing was 2.7% for zolpidem and 0.2% for ramelteon. Ramelteon and its metabolite (M-II) concentrations in the breast milk were equivalent to those in the maternal serum, although the infant exposure of these drugs was low for an oral dose. Conclusions: In the current case, zolpidem transferred into the placenta and breast milk, and ramelteon transferred into the breast milk. Further studies should assess the safety of zolpidem and ramelteon in fetus and breastfed infants.

Determination of zolpidem phenyl-4-carboxylic acid and zolpidem 6-carboxylic acid in hair using gas chromatography-electron ionization-tandem mass spectrometry.

A gas chromatography-electron ionization-tandem mass spectrometric (GC-EI-MS/MS) method was developed and validated for determination of the major metabolites of zolpidem, zolpidem phenyl-4-carboxylic acid (ZPCA) and zolpidem 6-carboxylic acid (ZCA) in human hair. The sample preparation procedure involves decontamination, mechanical pulverization, incubation, extraction and purification prior to instrumental analysis. The extracts were derivatized using hexafluoroisopropanol and heptafluorobutyric anhydride and analyzed by GC-EI-MS/MS. The linear ranges were 8-100 pg/mg for ZPCA and 16-200 pg/mg for ZCA, with the correlation coefficients >0.997. The limits of detection were 1.8 pg/mg for ZPCA and 1.7 pg/mg for ZCA. The recoveries ranged from 77.6 to 111.7%. The intra- and inter-day precisions were within 16.9 and 11.7%, while intra- and inter-day accuracies were -7.0-8.7 and -2.8-7.8%, respectively. The developed method was applied for the analysis of forensic hair samples obtained from suspected zolpidem abusers and the following concentration ranges were monitored: ZPCA 11.9-35.9 pg/mg and ZCA 16.6-21.8 pg/mg. The method proved to be suitable for picogram-level determination of ZPCA and ZCA in human hair.

Development and Validation of an LC-MS-MS Method for the Detection of 40 Benzodiazepines and Three Z-Drugs in Blood and Urine by Solid-Phase Extraction.

An analytical method for the detection of 40 benzodiazepines, (±)-zopiclone, zaleplon and zolpidem in blood and urine by solid-phase extraction liquid chromatography-tandem mass spectrometry was developed and validated. Twenty-nine of 43 analytes were quantified in 0.5 mL whole blood for investigating postmortem, drug-facilitated sexual assault (DFSA) and driving under the influence of drugs cases (DUID). The four different dynamic ranges of the seven-point, linear, 1/x weighted calibration curves with lower limits of quantification of 2, 5, 10 and 20 µg/L across the analytes encompassed the majority of our casework encountered in postmortem, DFSA and DUID samples. Reference materials were available for all analytes except α-hydroxyflualprazolam, a hydroxylated metabolite of flualprazolam. The fragmentation of α-hydroxyflualprazolam was predicted from the fragmentation pattern of α-hydroxyalprazolam, and the appropriate transitions were added to the method to enable monitoring for this analyte. Urine samples were hydrolyzed at 55°C for 30 min with a genetically modified ß-glucuronidase enzyme, which resulted in >95% efficiency measured by oxazepam glucuronide. Extensive sample preparation included combining osmotic lysing and protein precipitation with methanol/acetonitrile mixture followed by freezing and centrifugation resulted in exceptionally high signal-to-noise ratios. Bias and between-and within-day imprecision for quality controls (QCs) were all within ±15%, except for clonazolam and etizolam that were within ±20%. All 29 of the 43 analytes tested for QC performance met quantitative reporting criteria within the dynamic ranges of the calibration curves, and 14 analytes, present only in the calibrator solution, were qualitatively reported. Twenty-five analytes met all quantitative reporting criteria including dilution integrity. The ability to analyze quantitative blood and qualitative urine samples in the same batch is one of the most useful elements of this procedure. This sensitive, specific and robust analytical method was routinely employed in the analysis of >300 samples in our laboratory over the last 6 months.

Simultaneous determination of 75 abuse drugs including amphetamines, benzodiazepines, cocaine, opioids, piperazines, zolpidem and metabolites in human hair samples using liquid chromatography-tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometric method for the simultaneous determination of 75 abuse drugs and metabolites, including 19 benzodiazepines, 19 amphetamines, two opiates, eight opioids, cocaine, lysergic acid diethylamide, zolpidem, three piperazines and 21 metabolites in human hair samples, was developed and validated. Ten-milligram hair samples were decontaminated, pulverized using a ball mill, extracted with 1 mL of methanol spiked with 28 deuterated internal standards in an ultrasonic bath for 60 min at 50°C, and purified with Q-sep dispersive solid-phase extraction tubes. The purified extracts were evaporated to dryness and the residue was dissolved in 0.1 mL of 10% methanol. The 75 analytes were analyzed on an Acquity HSS T3 column using gradient elution of methanol and 0.1% formic acid and quantified in multiple reaction monitoring mode with positive electrospray ionization. Calibration curves were linear (r ≥ 0.9951) from the lower limit of quantitation (2-200 pg/mg depending on the drug) to 2000 pg/mg. The coefficients of variation and accuracy for intra- and inter-assay analysis at three QC levels were 4.3-12.9% and 89.2-109.1%, respectively. The overall mean recovery ranged from 87.1 to 105.3%. This method was successfully applied to the analysis of 11 forensic hair samples obtained from drug abusers.

Probing the molecular basis for affinity/potency- and efficacy-based subtype-selectivity exhibited by benzodiazepine-site modulators at GABAA receptors.

The extracellular α(+)/γ2(-) interface in the α1,2,3,5ßγ2 GABAA receptor harbours the allosteric binding site targeted by benzodiazepines and newer generations of subtype-selective modulators. We have probed the molecular determinants for the affinity/potency-based α1-preference exhibited by the hypnotic zolpidem (Ambien®, Stilnox®) and the efficacy-based α3-over-α1 selectivity displayed by the analgesic NS11394. Binding affinities and functional properties of the modulators were characterized at wild-type, concatenated, mutant and chimeric α1,3ß2γ2S receptors expressed in tsA201 cells and Xenopus oocytes by [3H]flumazenil binding and two-electrode voltage clamp electrophysiology. Substitution of Gly201 in α1 with the corresponding Glu in α3 completely eliminated the α1-over-α3 preference exhibited by zolpidem. In contrast, the reverse α3-E225G mutation did not yield corresponding increases in the binding affinity or modulatory potency of zolpidem at α3ß2γ2S, and two additional molecular elements in the extracellular domain of the α-subunit were found also to contribute to its α1-preference. Interestingly, the α1-Gly201/α3-Glu225 residue was also a key determinant of the efficacy-based α3-over-α1 selectivity exhibited by NS11394, and a pronounced correlation existed between the side-chain bulkiness of this residue and the modulatory efficacy of NS11394 at the receptor. The subtype-selectivity determinants identified for zolpidem and NS11394 were found also to apply in different degrees to the α1-preferring modulator indiplon and the α3-over-α1 selective modulator L-838,417, respectively. In conclusion, the molecular origins of subtype-selectivity exhibited by benzodiazepine-site modulators at the α1,2,3,5ßγ2 GABAA receptor seem more complex than previously appreciated, and the importance of the α1-Gly201/α3-Glu225 residue for both potency- and efficacy-based subtype-selective modulation through this site is likely to be rooted in different molecular mechanisms.