Analyses of benzodiazepines and their metabolites in various biological matrices by LC-MS(/MS)

Probe Electrospray Ionization Tandem Mass Spectrometry for the Detection and Quantification of Benzodiazepines

BACKGROUND

Legally prescribed benzodiazepines (BZDs) and designer BZDs are widely misused and must be determined in multiple contexts (eg, overdose, drug-facilitated sexual assaults, or driving under the influence of drugs). This study aimed to develop a method for measuring serum BZD levels using probe electrospray ionization (PESI) mass spectrometry and an isotope dilution approach.

METHODS

A tandem mass spectrometer equipped with a probe electrospray ionization source in multiple reaction monitoring mode was used. Isotope dilution was applied for quantification using a deuterated internal standard at a fixed concentration for alprazolam, bromazepam, diazepam, nordiazepam, oxazepam, temazepam, zolpidem, and zopiclone. This method included designer BZDs: clonazolam, deschloroetizolam, diclazepam, etizolam, flualprazolam, flubromazepam, flubromazolam, meclonazepam, nifoxipam, and pyrazolam. Sample preparation was done by mixing 10 µL of serum with 500 µL of an ethanol/ammonium formate 0.01 mol/L buffer. Complete validation was performed, and the method was compared with liquid chromatography coupled with mass spectrometry (LC-MS/MS) and immunoassays (IC) by analyzing 40 real samples.

RESULTS

The analysis time for identification and quantification of the 18 molecules was 2.5 minutes. This method was fully validated, and the limits of quantification varied from 5 to 50 mcg/L depending on the molecule. In the 40 real samples, 100% of molecules (n = 89) were detected by both LC-MS/MS and PESI-MS/MS, and regression analysis showed excellent agreement between the 2 methods (r 2 = 0.98). On IC, bromazepam and zolpidem were not detected in 2 and 1 cases, respectively.

CONCLUSIONS

PESI-MS/MS allows serum BZD detection and measurement. Given the isotope dilution approach, a calibration curve was not required, and its performance was similar to that of LC-MS/MS, and its specificity was higher than that of IC.

Recent findings and advancements in the detection of designer benzodiazepines: a brief review

This review article takes a closer look at a new class of psychoactive substances called designer benzodiazepines (DBZs) and the challenges of their detection. These are adinazolam, clonazolam, deschloroetizolam, diclazepam, etizolam, flualprazolam, flubromazepam, flubromazolam, phenazepam, and pyrazolam. They are central nervous system depressants and sedatives that can cause psychomotor impairment and increase the overdose risk when combined with other sedatives. DBZs undergo phase I and II metabolism similar to traditional benzodiazepines, but their specific metabolic pathways and the influence of genetic polymorphisms are yet to be clarified. Advances in liquid chromatography-tandem mass spectrometry (LC-MS/MS) have enhanced the method's sensitivity for DBZs and their metabolites in biological samples and coupled with improved blood sampling methods require less blood for drug monitoring. Further research should focus on elucidating their pharmacokinetic properties and metabolism in humans, especially in view of genetic polymorphisms and drug interactions that could inform clinical treatment choices. Even though we have witnessed important advances in DBZ detection and measurement, further refinements are needed to expand the scope of detectable DBZs and their metabolites. All this should help toxicological research to better identify and characterise the risks of chronic and polydrug abuse and facilitate clinical, forensic, and regulatory responses to this growing issue.

Quantification of 54 Benzodiazepines and Z-Drugs, Including 20 Designer Ones, in Plasma

Benzodiazepines are widely used in the treatment of sleep and anxiety disorders, as well as epileptic seizures and alcohol withdrawal because of their broad therapeutic index and low cost. Due to their central nervous system depressant effects they are also often implicated in traffic accidents and drug-related intoxications. With an increasing number of designer benzodiazepines used in a recreational setting, there is a need for analytical methods to be able to quantify both the prescribed and designer benzodiazepines. A liquid chromatography-triple quadrupole mass spectrometry method was developed for the quantification of 34 prescribed and 20 designer benzodiazepines in plasma. Different sample preparation strategies, including protein precipitation, liquid-liquid extraction, solid-phase extraction and mini-QuEChERS, were tested. The best recoveries for all compounds of interest were obtained with a liquid-liquid extraction using methyl-tertiary-butyl-ether and 500 μL plasma. The method was fully validated according to the European Medicines Agency guidelines for all compounds, except pivoxazepam, which is included for qualitative purposes only. In-sample stability issues were observed for cloxazolam, both at ambient temperature and during long-term storage at -20°C. Due to the large number of compounds included, the simple and time-efficient sample preparation and the relatively inexpensive instrumentation used, the presented method can be readily implemented in both therapeutic drug monitoring and forensic analyses.

Hair as a matrix in monitoring drug epilepsy therapy

Hair is considered an efficient tool to investigate drug-related histories; thus, the selection of the method of sample preparation is important to obtain a reliable result. The aim of this study was to compare two methods of hair preparation (cutting and pulverizing) to analyse levetiracetam concentration in hair. An additional aim was to evaluate the potential usefulness of the levetiracetam concentration measured as an index of a dosing schedule. Four groups of 12 rats were included in the experiment. Depending on the group, the rats received 10 mg/kg of levetiracetam intraperitoneally every 24, 48 and 72 hours for 30 days. The control group was not treated. At the end of the drug administration, the rats' hair was shaved, cut or pulverized and analysed by the LC/MS-MS method to determine the concentration of levetiracetam. A stronger correlation between the mean hair levetiracetam concentration in hair and the number of drug doses was found in pulverized hair than in cut hair. A smaller standard deviation between the results was obtained in the case of pulverized hair. The results indicate that pulverization gives a more reliable result of drug concentration in hair than cutting and that drug concentration in hair can reflect the scheme of levetiracetam administration.

HPLC methods for quantifying anticancer drugs in human samples: A systematic review

Pharmacokinetic (PK) study of anticancer drugs in cancer patients is highly crucial for dose selection and dosing intervals in clinical applications. Once an anticancer drug is administered, it undergoes various metabolic pathways; to determine these pathways, it is necessary to follow the administered drug in biological samples via different analytical methods. In addition, multi-drug quantification methods in patients undergoing multi-drug regimens of cancer therapy can have several benefits, such as reduced sampling time and analysis costs. In order to collect and categorize these studies, we conducted a systematic review of HPLC methods reported for the analysis of anticancer drugs in biological samples. A systematic search was performed on PubMed Medline, Scopus, and Web of Science databases, and 116 studies were included. In summary of included studies, when the objective of a method was to quantify a single drug, MS, or UV detectors were utilized equivalently. On the other hand, in methods with the aim of quantifying drug and metabolite(s) in a single run, MS detectors were the most utilized. This review can provide a comprehensive insight for researchers prior to developing a quantification method and selecting a detector.

Kinetic profile of N,N-dimethyltryptamine and β-carbolines in saliva and serum after oral administration of ayahuasca in a religious context

Ayahuasca is a beverage obtained from Banisteriopsis caapi plus Psychotria viridis. B. caapi contains the β-carbolines harmine, harmaline, and tetrahydroharmine that are monoamine oxidase inhibitors and P. viridis contains N,N-dimethyltryptamine (DMT) that is responsible for the visionary effects of the beverage. Ayahuasca use is becoming a global phenomenon, and the recreational use of DMT and similar alkaloids has also increased in recent years; such uncontrolled use can lead to severe intoxications. In this investigation, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to study the kinetics of alkaloids over a 24 h period in saliva and serum of 14 volunteers who consumed ayahuasca twice a month in a religious context. We compared the area under the curve (AUC), maximum concentration (C_max ), time to reach C_max (T_max ), mean residence time (MRT), and half-life (t_1/2 ), as well as the serum/saliva ratios of these parameters. DMT and β-carboline concentrations (C_max ) and AUC were higher in saliva than in serum and the MRT was 1.5-3.0 times higher in serum. A generalized estimation equations (GEEs) model suggested that serum concentrations could be predicted by saliva concentrations, despite large individual variability in the saliva and serum alkaloid concentrations. The possibility of using saliva as a biological matrix to detect DMT, β-carbolines, and their derivatives is very interesting because it allows fast noninvasive sample collection and could be useful for detecting similar alkaloids used recreationally that have considerable potential for intoxication.

Determination of the alcohol biomarker phosphatidylethanol 16:0/18:1 and 33 compounds from eight different drug classes in whole blood by LC-MS/MS

INTRODUCTION

Most bioanalytical LC-MS/MS methods are developed for determination of single drugs or classes of drugs, but a multi-compound LC-MS/MS method that can replace several methods could reduce both analysis time and costs. The aim of this study was to develop a high-throughput LC-MS/MS method for determination of the alcohol biomarker phosphatidylethanol 16:0/18:1 (PEth 16:0/18:1) and 33 other compounds from eight different drug classes in whole blood.

METHODS

Whole-blood samples were prepared by 96-well supported liquid extraction (SLE). Chromatographic separations were performed on a biphenyl core shell column with a mobile phase consisting of 10 mM ammonium formate, pH 3.1 and methanol. Each extract was analyzed twice by LC-MS/MS, injecting 0.4 μL and 2 μL, in order to obtain narrow and symmetrical peaks and good sensitivity for all compounds. Stable isotope-labeled internal standards were used for 31 of the 34 compounds.

RESULTS

A 96-well SLE reversed phase LC-MS/MS method for determination of PEth 16:0/18:1 and 33 other compounds from eight different drug classes was developed and validated. By using an organic solvent mixture of isopropanol/ methyl tert-butyl ether (1:5, v:v), all compounds, including the polar and ampholytic compounds pregabalin, gabapentin and benzoylecgonine, was extracted by 96-well SLE.

DISCUSSION/CONCLUSION

For the first time an LC-MS/MS method for the determination of alcohol biomarker PEth 16:0/18:1 and drugs and metabolites from several different drug classes was developed and validated. The developed LC-MS/MS method can be used for high-throughput analyses and sensitive determinations of the 34 compounds in whole blood.

Characterization and tentative identification of new flunitrazepam metabolites in authentic human urine specimens using liquid chromatography-Q exactive-HF hybrid quadrupole-Orbitrap-mass spectrometry (LC-QE-HF-MS)

Flunitrazepam (FNZ) is a potent hypnotic, sedative, and amnestic drug used to treat severe insomnia. In our recent study, FNZ metabolic profiles were investigated carefully. Six authentic human urine samples were purified using solid phase extraction (SPE) without enzymatic hydrolysis, and urine extracts were then analyzed by liquid chromatography-Q exactive-HF hybrid quadrupole-Orbitrap-mass spectrometry (LC-QE-HF-MS), using the full scan positive ion mode and targeted MS/MS (ddms2) technique to make accurate mass measurements. There were 25 metabolites, including 13 phase I and 12 phase II metabolites, which were detected and tentatively identified by LC-QE-HF-MS. In addition, nine previously unreported phase II glucuronide conjugates and four phase I metabolites are reported here for the first time. Eight metabolic pathways, including N-reduction and O-reduction, N-glucuronidation, O-glucuronidation, mono-hydroxylation and di-hydroxylation, demethylation, acetylation, and combinations, were implicated in this work, and 2-O-reduction together with dihydroxylation were two novel metabolic pathways for FNZ that were identified tentatively. Although 7-amino FNZ is widely considered to be the primary metabolite, a previously unreported metabolites (M12) can also serve as a potential biomarker for FNZ misuse.

Acidic transformation of nordiazepam can affect recovery estimate during trace analysis of diazepam and nordiazepam in environmental water samples by liquid chromatography-tandem mass spectrometry

In this study, a special interest was focused on the stability of diazepam and nordiazepam in aqueous samples at acidic and neutral pH. The aim of the study was to isolate and illustrate one of the many possible sources of error that can be encountered when developing and validating analytical methods. This can be of particular importance when developing multi-analyte methods where there is limited time to scrutinize the behavior of each analyte. A method was developed for the analysis of the benzodiazepines diazepam and nordiazepam in treated wastewater. The samples were extracted by solid phase extraction, using SPEC C18AR cartridges, and analyzed by the use of liquid chromatography, with a C18 stationary phase, coupled to tandem mass spectrometry. Environmental water samples are often acidified during storage to reduce the microbial degradation of the target compounds and to preserve the sample. In some cases, the samples are acidified before extraction. In this study, it was found that a chemical equilibrium between nordiazepam and a transformation product could cause inaccurately high extraction recovery values when the samples were stored at low sample pH. The stability of nordiazepam was shown to be low at pH 3. Within 12 days, 20% of the initial concentration of nordiazepam was transformed. Interestingly, the transformed nordiazepam was shown to be regenerated and reformed to nordiazepam during sample handling. At a sample pH of 7, diazepam and nordiazepam were stable for 12 days. It was concluded that great care must be taken when acidifying water samples containing nordiazepam during storage or extraction. The storage and the extraction should be conducted at neutral pH if no internal standard is used to compensate for degradation and conversion of nordiazepam. The developed method was validated in treated wastewater and applied for the quantification of diazepam and nordiazepam in treated wastewater samples.

Determination of β-Agonist Residues in Animal-Derived Food by a Liquid Chromatography-Tandem Mass Spectrometric Method Combined with Molecularly Imprinted Stir Bar Sorptive Extraction

A novel clenbuterol molecularly imprinted polymer (MIP)-coated stir bar was prepared and applied to the determination of six β-agonists in animal-derived food. Characterization and various parameters affecting adsorption and desorption behaviours were investigated. The extraction capacities of clenbuterol, salbutamol, ractopamine, mabuterol, brombuterol, and terbutaline for MIP coating were 3.8, 2.9, 3.1, 3.5, 3.2, and 3.3 times higher, respectively, than those of the NIP coating, respectively. The method of MIP-coated SBSE coupled with HPLC-MS/MS was developed. The recoveries in pork and liver samples were 75.8-97.9% with RSD from 2.6 to 5.3%. Limits of detection (LODs) and limits of quantification (LOQs) were 0.05-0.15 μg/kg and 0.10-0.30 μg/kg, respectively. Good linearities were obtained for six β-agonists with correlation coefficients (R²) higher than 0.994. These results indicated the superiority of the proposed method in the analysis of β-agonists in a complex matrix.

Loss of atomic nitrogen from even-electron ions? A study on benzodiazepines

The fragment spectra of protonated nitro-substituted benzodiazepines show an unusual fragment [M + H - 14]⁺ , which is shown by accurate mass measurement to be due to the loss of a nitrogen atom. Our investigations show that this apparent loss of atomic nitrogen is rather an attachment of molecular oxygen to the [M + H - NO₂ ]^+• ion, which is the main fragment ion in these spectra. The oxygen attachment is exothermic, and rate constants have been derived. MSⁿ spectra show that it is not easily reversible upon fragmentation of the adduct ion and that it is also observed with some secondary and tertiary fragments, which allows to limit the attachment site to the aromatic ring annulated to the diazepine moiety. Fragments of the oxygen adduct ion indicate that the O₂ molecule dissociates in the adduct formation process, and the two oxygen atoms are bound to different sites of the ion. Comparison with radical cations generated by fragmentation of non-nitro-substituted benzodiazepines, none of which showed an oxygen attachment, and the fragmentation mechanisms involved in their formation indicates that the [M + H - NO₂ ]^+• ion is a distonic ion with the charge and radical site neighbored on the aromatic ring. From these results, we derive a proposal for the formation and structure of the [M + H - NO₂  + O₂ ]^+• ion, which explains the experimental observations. Copyright © 2015 John Wiley & Sons, Ltd.

Development and validation of an ultra-performance liquid chromatography method coupled with tandem mass spectrometry for determination of alizapride in human plasma

Representative (a) blank plasma samples, (b) spiked plasma sample at LLQQ (1 ng mL⁻¹) with the IS, (c) spiked plasma sample at QCH (800 ng mL⁻¹) with the IS and (d) real plasma sample at 10 minutes spiked with the IS.

Parts per trillion detection of 7-aminonitrazepam by nano-enhanced ELISA

It is challenging to detect 7-aminonitrazepam (7-ANZP) residue in animal tissues simply and sensitively by the enzyme-linked sorbent immunoassay (ELISA) method. This paper demonstrates that utilizing a bioconjugate of gold nanoparticles and enzyme-labeled antibody as a signal probe increases the sensitivity of a traditional ELISA for 7-ANZP by nearly 20 times. The sensitivity of this ELISA for 7-ANZP was 5.6 pg/mL in buffer, and the limit of detection (LOD) of 0.18 μg/kg for 7-ANZP in urine could be achieved after the urine samples were simply hydrolyzed and diluted by buffer. This simple and sensitive method has potential application for improving the sensitivity of ELISA methods against various small molecules.

Metabolite structure analysis by high-resolution MS: supporting drug-development studies

Effective characterization of drug metabolites in complex biological matrices is facilitated by mass spectrometers with high resolving power, mass accuracy and sensitivity. This review begins with an overview of high-resolution MS terminology and the different types of instrumentation that are currently available. Metabolite structure analysis offers unique challenges and, therefore, the different types of approaches used to solve problems are highlighted through specific examples. Overall, this review describes the value that high-resolution MS brings to drug-metabolism studies.

A fast liquid chromatography-tandem mass spectrometry method for determining benzodiazepines and analogues in urine. Validation and application to real cases of forensic interest

A fast liquid chromatographic/tandem mass spectrometric method was developed for the simultaneous determination in human urine of seventeen benzodiazepines, four relevant metabolites together plus zolpidem and zopiclone. The sample preparation, optimized to take into account the matrix effect, was based on enzymatic hydrolysis and liquid-liquid extraction. The separation of the twenty-three analytes was achieved in less than eight minutes. The whole methodology was fully validated according to UNI EN ISO/IEC 17025:2005 rules and 2006 SOFT/AAFS guidelines. Selectivity, linearity range, identification (LOD) and quantitation (LOQ) limits, precision, accuracy and recovery were evaluated. For all the species the signal/concentration linearity was satisfactory in the 50-1000 ng/mL concentration range. The limits of detection ranged from 0.5 to 30 ng/mL and LOQs from 1.7 to 100.0 ng/mL. Precisions were in the ranges 5.0-11.8%, 1.5-11.0% and 1.1-4.4% for low (100 ng/mL), medium (300 ng/mL) and high (1000 ng/mL) concentration, respectively. The accuracy, expressed as bias% was within ± 25 % for all the analytes. The recovery values, evaluated at 300 ng/mL concentration, ranged from 56.2% to 98.8%. The present method for the determination of several benzodiazepines, zolpidem and zopiclone in human urine proved to be simple, fast, specific and sensitive. The quantification by LC-MS/MS was successfully applied to 329 forensic cases among driving re-licensing, car accidents and alleged sexual violence cases.