Simultaneous analysis of flunitrazepam and its major metabolites in human plasma by high performance liquid chromatography tandem mass spectrometry

Metabolites replace the parent drug in the drug arena. The cases of fonazepam and nifoxipam

Fonazepam (desmethylflunitrazepam) and nifoxipam (3-hydroxy-desmethylflunitrazepam) are benzodiazepine derivatives and active metabolites of flunitrazepam. They recently invaded the drug arena as substances of abuse and alerted the forensic community after being seized in powder and tablet forms in Europe between 2014 and 2016. A review of all the existing knowledge of fonazepam and nifoxipam is reported, concerning their chemistry, synthesis, pharmacology and toxicology, prevalence/use, biotransformation and their analysis in biological samples. To our knowledge, fonazepam and nifoxipam-related intoxications, lethal or not, have not been reported in the scientific literature. All the available information was gathered through a detailed search of PubMed and the World Wide Web.

Analytical methods for determination of benzodiazepines. A short review

Benzodiazepines (BDZs) are generally commonly used as anxiolytic and/or hypnotic drugs as a ligand of the GABAA-benzodiazepine receptor. Moreover, some of benzodiazepines are widely used as an anti-depressive and sedative drugs, and also as anti-epileptic drugs and in some cases can be useful as an adjunct treatment in refractory epilepsies or anti-alcoholic therapy. High-performance liquid chromatography (HPLC) methods, thin-layer chromatography (TLC) methods, gas chromatography (GC) methods, capillary electrophoresis (CE) methods and some of spectrophotometric and spectrofluorometric methods were developed and have been extensively applied to the analysis of number of benzodiazepine derivative drugs (BDZs) providing reliable and accurate results. The available chemical methods for the determination of BDZs in biological materials and pharmaceutical formulations are reviewed in this work.

Intermolecular Interactions between Eosin Y and Caffeine Using 1H-NMR Spectroscopy

DETECHIP has been used in testing analytes including caffeine, cocaine, and tetrahydrocannabinol (THC) from marijuana, as well as date rape and club drugs such as flunitrazepam, gamma-hydroxybutyric acid (GHB), and methamphetamine. This study investigates the intermolecular interaction between DETECHIP sensor eosin Y (DC1) and the analyte (caffeine) that is responsible for the fluorescence and color changes observed in the actual array. Using ¹H-NMR, ¹H-COSY, and ¹H-DOSY NMR methods, a proton exchange from C-8 of caffeine to eosin Y is proposed.

Simultaneous quantification of urine flunitrazepam, nimetazepam and nitrazepam by using liquid chromatography tandem mass spectrometry

BACKGROUND

Benzodiazepines are used in hypnotics, sedation, and anti-anxiety. Recently liquid chromatography tandem mass spectrometry (LC-MS/MS) has been vastly developed for drug analysis in biological samples.

METHODS

We developed and validated a LC-MS/MS method for simultaneous quantification of flunitrazepam (FM2), nimetazepam and nitrazepam levels in 87 benzodiazepine positive human urine specimens by enzyme immunoassay. Deuterated analogues were used as internal standard.

RESULTS

The limits of quantification were found to be 0.25, 2.5, 5, 5 and 1ng/ml for FM2, 7-aminoFM2, nimetazepam, 7-amino-nimetazepam and nitrazepam, respectively. The intraday and inter-day CVs ranged from 0.6 to 4.6% and 1.2-9.4%, respectively. The within-day accuracy ranged from 80.8 to 108.7% and the between-day accuracy ranged from 80.5 to 118.0%. The recovery rate ranged from 70.5 to 96.7% for five different analytes. A group of 34 urine samples previously gas chromatography-mass spectrometry determined to contain 7-aminoFM2 was analyzed by this new LC-MS/MS approach. Quantitative data produced by both methods agreed well.

CONCLUSIONS

The LC-MS/MS method has proved to be robust and specific for the quantification of FM2, nimetazepam and nitrazepam in urine samples. This study also confirmed that nitrazepam and 7-aminonimetazepam are the metabolic products of nimetazepam.

Digital Image Analysis for DETCHIP® Code Determination

DETECHIP^® is a molecular sensing array used for identification of a large variety of substances. Previous methodology for the analysis of DETECHIP^® used human vision to distinguish color changes induced by the presence of the analyte of interest. This paper describes several analysis techniques using digital images of DETECHIP^®. Both a digital camera and flatbed desktop photo scanner were used to obtain Jpeg images. Color information within these digital images was obtained through the measurement of red-green-blue (RGB) values using software such as GIMP, Photoshop and ImageJ. Several different techniques were used to evaluate these color changes. It was determined that the flatbed scanner produced in the clearest and more reproducible images. Furthermore, codes obtained using a macro written for use within ImageJ showed improved consistency versus pervious methods.

A rapid UPLC-MS/MS method for simultaneous determination of flunitrazepam, 7-aminoflunitrazepam, methadone and EDDP in human, rat and rabbit plasma

A simple, high-throughput, sensitive LC-ESI-MS/MS method is presented for the simultaneous determination of methadone (MET), flunitrazepam (FNZ) and their major metabolites, EDDP (2-ethilidene-1,5-dimethyl-3,3-diphenylpyrrolidone) and 7-aminoflunitrazepam (7-AFNZ), respectively, in human, rat and rabbit plasma. The isolation of the selected compounds involved a liquid-liquid extraction with ethyl acetate at a basic pH. Good chromatographic separation was achieved on a HSS T3 column (1.8 μm particle size), with a 3 min gradient elution using a mixture of acetonitrile with 0.1% formic acid (solvent A) and 5mM ammonium acetate (solvent B) as the mobile phase. The tandem mass spectrometric detection was performed in multiple reaction monitoring (MRM) mode with ionization of the analytes in positive mode. The assay was fully validated according to current acceptance criteria for bioanalytical methods validation. It was proved to be linear in the range of 0.5-250 ng/mL, with adequate accuracy and precision over this range. Based on accuracy and CV% values the LOQ and ULOQ values were set at 0.509 ng/mL and 2036 ng/mL for MET, 0.520 ng/mL and 2080 ng/mL for EDDP, 0.524 ng/mL and 2096 ng/mL for FNZ and 0.528 ng/mL and 2114 ng/mL for 7-AFNZ, respectively. The method was tested for potential matrix effects, without observing significant ion suppression. The investigated compounds stability was examined in plasma at room temperature and after three freeze-thaw cycles and in the final extract when maintained at 4 °C in the autosampler. Potential stability issues were observed only for FNZ at room temperature. The method was successfully applied to quantify the selected compounds in human, rat and rabbit plasma samples, after exposure to FNZ or simultaneous exposure to FNZ and MET.

Benzodiazepines: sample preparation and HPLC methods for their determination in biological samples

Benzodiazepines (BDZs) belong to a group of substances known for their sedative, antidepressive, muscle relaxant, tranquilizer, hypnotic and anticonvulsant properties. Their determination in biological fluids is essential in clinical assays as well as in forensics and toxicological studies. Researchers focus on the development of rapid, accurate, precise and sensitive methods for the determination of BDZs and their metabolites. A large number of analytical methods using different techniques have been reported, but none can be considered as the method of choice. BDZs are usually present at trace levels (microgram or nanogram per milliliter) in a complex biological matrix and the potentially interfering compounds must be isolated by various extraction techniques before analysis. An extended and comprehensive review is presented herein, focusing on sample preparation (pretreatment and extraction) and HPLC conditions applied by different authors. These methods enable bioanalysts to achieve detection limits down to 1-2 ng/ml using UV/diode array detection, readily available in most laboratories, and better than 1 ng/ml using electron capture detection, which is lower than that obtained using a nitrogen phosphorus detector. MS interfaced with electrospray ionization offered a similar sensitivity, while negative chemical ionization MS or sonic spray ionization MS provided sensitivity down to 0.1 ng/ml.

Enantiodiscrimination of methamphetamine by circular dichroism using a porphyrin tweezer

Using exciton-coupled circular dichroism (ECCD) spectroscopy, our lab was able to differentiate between the two enantiomers of methamphetamine using a commercially available porphyrin tweezer as an achiral host. The host-guest complex formed with (+)-(S)-methamphetamine produced a negative bisignate-shaped ECCD spectrum, whereas the complex formed with (-)-(R)-methamphetamine produced a positive one. This sensitive technique could serve as an alternative method for the enantiodiscrimination of chiral methamphetamine, a commonly abused drug in the United States.

DETECHIP: a sensor for drugs of abuse

The design and preliminary characterization of a novel sensor for drugs of abuse, DETECHIP, is described in this proof-of-concept note. Combining both colorimetric and fluorimetric assays, DETECHIP is suitable for lab and field use. More than a conventional spot test which provides a single "yes or no" answer, DETECHIP provides twenty responses for a more complete characterization of suspect material. This is accomplished by visually noting colorimetric and fluorescent changes of carefully selected dyes upon the addition of test analytes, including drugs of abuse, with respect to controls. Color and fluorescence changes are recorded numerically so that a 20 digit identification code can be constructed for comparison of test analytes and known compounds. DETECHIP is applicable to a variety of drugs, both plant-derived and synthetic, addressing the need to use several different spot tests simultaneously for a single sample.

The Effects of Benzodiazepines on Orexinergic Systems in Rat Cerebrocortical Slices

BACKGROUND

As orexinergic (OXergic) neurons have been reported to mediate emotional changes, benzodiazepines might interact with OXergic neurons.

METHODS

We examined the interactions between OXergic neurons and benzodiazepine receptors in orexin-A (100 nM) and K+ (25 mM)-evoked norepinephrine release from rat cerebrocortical slices.

RESULTS

Midazolam, diazepam, and flunitrazepam concentration-dependently inhibited both OX-A- and K+-evoked norepinephrine release. The IC50 of midazolam for orexin-A-evoked release (0.87 microM, P < 0.01), which was insensitive to flumazenil, was significantly lower than that of diazepam and flunitrazepam (around 60 microM), whereas the IC50s for K+-evoked release were not different among the benzodiazepines.

CONCLUSION

There may be no interaction between OXergic neurons and central benzodiazepine receptors.

Sweeping technique combined with micellar electrokinetic chromatography for the simultaneous determination of flunitrazepam and its major metabolites

A sweeping technique, in conjunction with micellar electrokinetic chromatography, for the simultaneous determination of flunitrazepam and its major metabolites, 7-aminoflunitrazepam and N-desmethylflunitrazepam, is described. The optimized conditions for the sweeping and separation were a pH 9.5 buffer, 25mM borate, 50mM cetyltrimethylammonium bromide, 30% MeOH (v/v), and a 151-mm injection length. The calibration functions were all linear with the coefficient of determination (r(2)) exceeding 0.996 for the three target compounds. Using the sweeping procedure, the limits of detection were determined to be 13.4, 5.6, and 12.0ng/mL for flunitrazepam, 7-aminoflunitrazepam, and N-desmethylflunitrazepam, respectively, and the sensitivity enhancement for each compound was within the range of 110-200 fold. The RSDs for the retention time and the peak area were less than 4.10%. The optimized sweeping method was also used to examine a spiked urine sample. We conclude that sweeping with micellar electrokinetic chromatography has considerable potential use in clinical and forensic analyses of flunitrazepam and its metabolites.

Simultaneous determination of flunitrazepam and 7-aminoflunitrazepam in human serum by ion trap gas chromatography-tandem mass spectrometry

A method for the determination of flunitrazepam (FNZ) and 7-aminoflunitrazepam (7-AFNZ) in human serum was developed with ion trap gas chromatography (GC)-tandem mass spectrometry. The 7-AFNZ was derivatizated with 50 microl trifluoroacetic anhydride (TFAA), 60 degrees C-20 min. EI mass spectra and tandem mass spectra of FNZ and 7-AFNZ-TFA were m/z 238, 239, 266, 286, 294, 312, 313(M(+)), m/z 350, 351, 360, 378, 379(M(+)), m/z 238, 239, 240 (precursor ion m/z 286, collision energy 1.5 V), and m/z 239, 254, 264, 336 (precursor ion m/z 351, collision energy 1.8 V), respectively. The detection limits of full scan EI mass spectrometry and tandem mass spectrometry for FNZ and 7-AFNZ in human serum were ca. 200 ng/ml, 60 ng/ml, 15 ng/ml and 1 ng/ml, respectively.

Determination of 3'-C-ethynylcytidine in human plasma and urine by liquid chromatographic-electrospray ionization tandem mass spectrometry

A liquid chromatographic-electrospray ionization tandem mass spectrometric (LC-ESI/MS/MS) method was developed for the quantitative analysis of a novel anticancer drug, 3'-C-ethynylcytidine (I) in human plasma and urine. I and its stable isotope-labeled internal standard (II) were extracted from human plasma and urine samples using a polymer-based cation-exchange cartridge, and LC-ESI/MS/MS analysis was performed by monitoring the positive fragment ions of I and II. The linear ranges are 1-500 ng/ml in plasma and 10-5000 ng/ml in urine. The limits of quantitation for I were 1 ng/ml in plasma and 10 ng/ml in urine. The relative errors (RE) for I ranged from -8.4 to 3.0% in plasma and from 0.8 to 4.4% in urine. The relative standard deviations (RSD) for I ranged from 1.2 to 8.9% in plasma and from 0.7 to 2.8% in urine. This validated analytical method is demonstrated to be useful for the analysis of I in human plasma and urine in clinical studies.