Biochemical evaluation and ligand binding studies on glycerophosphodiester phosphodiesterase from Staphylococcus aureus using STD-NMR spectroscopy and molecular docking analysis.

Glycerophosphodiester phosphodiesterase (GDPD) is a highly conserved enzyme in both prokaryotic and eukaryotic organisms. It catalyses the hydrolysis of various glycerophosphodiesters into glycerol-3-phosphate and corresponding alcohols, which serve as building blocks in several biosynthetic pathways. This enzyme is a well-known virulence factor in many pathogenic bacteria, including Staphylococcus aureus, and is thus considered a potential drug target. In this study, competent E. coli BL21(DE3)pLysS expression cells were used to express the GDPD enzyme from vancomycin-resistant Staphylococcus aureus (VRSA), which was then purified using size exclusion and anion exchange chromatography. The hydrolytic activity of GDPD was evaluated on the non-physiological substrate bis(p-nitrophenyl) phosphate (BpNPP), which indicated functional activity of the enzyme. 79 drugs were evaluated for their inhibitory potential against GDPD enzyme by the colorimetric assay. Out of 79 drugs, 13 drugs, including tenofovir (1), adenosine (2), clioquinol (11), bromazepam (12), lamotrigine (13), sulfadiazine (14), azathioprine (15), nicotine (16), sitagliptin PO4 (17), doxofylline (18), clindamycin phosphate (19), gentamycin sulphate (20), and ceftriaxone sodium (21) revealed varying degrees of inhibitory potential with IC50 values in the range of 400 ± 0.007-951 ± 0.016 µM. All drugs were also evaluated for their binding interactions with the target enzyme by saturation transfer difference (STD-NMR) spectroscopy. 10 drugs demonstrated STD interactions and hence, showed binding affinity with the enzyme. Exceptionally, tenofovir (1) was identified to be a better inhibitor with an IC50 value of 400 ± 0.007 µM, as compared to the standard EDTA (ethylenediaminetetraacetic acid) (IC50 = 470 ± 0.008 µM). Moreover, molecular docking studies have identified key interactions of the ligand (tenofovir) with the binding site residues of the enzyme.

Postmortem Brain and Blood Reference Concentrations of Alprazolam, Bromazepam, Chlordiazepoxide, Diazepam, and their Metabolites and a Review of the Literature.

To interpret postmortem toxicology results, reference concentrations for non-toxic and toxic levels are needed. Usually, measurements are performed in blood, but because of postmortem redistribution phenomena this may not be optimal. Rather, measurement in the target organ of psychoactive drugs, the brain, might be considered. Here we present reference concentrations of femoral blood and brain tissue of selected benzodiazepines (BZDs). Using LC-MS/MS, we quantified alprazolam, bromazepam, chlordiazepoxide, diazepam, and the metabolites desmethyldiazepam, oxazepam and temazepam in postmortem femoral blood and brain tissue in 104 cases. BZDs were judged to be unrelated to the cause of death in 88 cases and contributing to death in 16 cases. No cases were found with cause of death solely attributed to BZD poisoning. All BZDs investigated tended to have higher concentrations in brain than in blood with median brain-blood ratios ranging from 1.1 to 2.3. A positive correlation between brain and blood concentrations was found with R(2) values from 0.51 to 0.95. Our reported femoral blood concentrations concur with literature values, but sparse information on brain concentration was available. Drug-metabolite ratios were similar in brain and blood for most compounds. Duplicate measurements of brain samples showed that the pre-analytical variation in brain (5.9%) was relatively low, supporting the notion that brain tissue is a suitable postmortem specimen. The reported concentrations in both brain and blood can be used as reference values when evaluating postmortem cases.

Environmental occurrence, fate and transformation of benzodiazepines in water treatment.

Benzodiazepine derivatives are prescribed in large quantities globally and are potentially new emerging environmental contaminants. Unfortunately, a dearth of data exists concerning occurrence, persistence and fate in the environment. This paper redresses this by reviewing existing literature, assessing the occurrence of selected benzodiazepine anxiolytics (diazepam, oxazepam and bromazepam) in wastewater influent and effluent and surface water from Slovenia, evaluating their removal during water treatment and identifying the transformation products formed during water treatment. Their occurrence was monitored in hospital effluent, river water and in wastewater treatment plant influent and effluent. The study reveals the presence of benzodiazepine derivatives in all samples with the highest amounts in hospital effluents: 111 ng L(-1), 158 ng L(-1) and 72 ng L(-1) for diazepam, bromazepam and oxazepam, respectively. Removal efficiencies with respect to biological treatment of diazepam were 16-18% (oxic), 18-32% (anoxic→oxic), 53-76% (oxic→anoxic) and 83% (oxic→anoxic→oxic→anoxic cascade bioreactors), while the removal oxazepam was 20-24% under anoxic conditions. Coupled biological and photochemical treatment followed by the adsorption to activated carbon resulted in a removal efficiency of 99.99%. Results reveal the recalcitrant nature of benzodiazepine derivatives and suggest that only combinational treatment is sufficient to remove them. In addition, eight novel diazepam and four novel oxazepam transformation products are reported.

Benzodiazepine metabolism: an analytical perspective.

Benzodiazepines are currently among the most frequently prescribed drugs all over the world. They act as anxiolytics, sedatives, hypnotics, amnesics, antiepileptics and muscle relaxants. Despite their common chemical scaffold, these drugs differ in their pharmacokinetic and metabolic properties. In particular, they are biotransformed by different cytochrome P450 isoforms and also by different UDP-glucuronosyltransferase subtypes. The most important studies on the metabolic characteristics of several 1,4-benzodiazepines, carried out from 1998 onwards, are reported and briefly discussed in this review. Moreover, the analytical methods related to these studies are also described and commented upon and their most important characteristics are highlighted. Most methods are based on liquid chromatography, which provides wide applicability and good analytical performance granting high precision, accuracy and feasibility. Mass spectrometry is gaining widespread acceptance, particularly if the matrix is very complex and variable, such as human or animal blood. However, spectrophotometric detection is still used for this purpose and can grant sufficient selectivity and sensitivity when coupled to suitable sample pre-treatment procedures. A monograph is included for each of the following benzodiazepines: alprazolam, bromazepam, brotizolam, clotiazepam, diazepam, etizolam, flunitrazepam, lorazepam, midazolam, oxazepam and triazolam.

Last performance with VIAGRA: post-mortem identification of sildenafil and its metabolites in biological specimens including hair sample.

A 43-year-old man was found dead in a hotel room during a sexual relation with a colleague.He was treated both for cardiovascular disease and for erectile dysfunction with VIAGRA. A pillbox was found in the room with several tablets of verapamil (Isoptine), trimetazidine (Vastarel), yohimbine and bromazepam (Lexomil). A box of VIAGRA 25mg was found in his raincoat and two tablets were missing. His wife declared during the investigation that he was also treated by trinitrine. Autopsy revealed severe coronary artery sclerosis as well as signs of previous myocardial infarctions. Blood, urine, bile, gastric content and hair and representative tissues for histology were collected for toxicological analysis. Sildenafil and yohimbine were screened with liquid chromatography/mass spectrometry (LC/MS) and trinitrine with headspace injection (HS)/GC/MS. Verapamil and trimetazidine were identified and quantified with LC/diode array detection (DAD). Sildenafil was identified in blood, urine, bile and gastric content at 105, 246, 1206 and 754ng/ml, respectively. Hair concentration was 177pg/mg. The desmethyl metabolite was quantified in urine at 143ng/ml. Blood concentrations of verapamil and trimetazidine were measured at 659 and 2133ng/ml, respectively and were above therapeutic ranges. Trinitrine and yohimbine were not identified. These results confirm the absorption of sildenafil, verapamil and trimetazidine before the death and hair analysis indicates the chronic use of sildenafil. To the author's knowledge, this is the first report of a fatal sildenafil-verapamil association, probably by hypotension and cardiac dysrhythmia.

Investigation into some aspects of EMIT d.a.u., TLC, and GC-MS urinalysis of bromazepam.

Among the different 1,4-benzodiazepine urinary metabolites, those of bromazepam possess distinctive chemical features that may be used in their selective isolation and detection. The detection of bromazepam metabolites in urine was carried out using EMIT d.a.u., thin-layer chromatography (TLC), and gas chromatography-mass spectrometry (GC-MS). The positive EMIT d.a.u. benzodiazepine assay for bromazepam was found to be due to the 3-hydroxybromazepam (3HOB) metabolite. The detection by TLC and GC-MS was carried out after enzyme or acid hydrolysis of the glucuronide conjugates. Both the 2-amino-3-hydroxy5-bromobenzoylpyridine (AHBBP) metabolite and the acid hydrolysis product of 3-HOB, 2-amino-5-bromobenzoylpyridine (ABBP), were selectively detected by TLC. The bromazepam metabolites in urine could be both isolated and detected selectively by GC-MS in the presence of the metabolites of other 1,4-benzodiazepines that were sometimes used in combination with bromazepam. Both 3-HOB and AHBBP were detected by GC-MS only after trimethylsilyl (TMS) derivatization and not as the free compounds or the acetyl derivatives. Only ABBP was detected in three forms: ABBP, the TMS derivative, and the acetyl derivative. Evidence has been obtained from the enzyme hydrolysis and the TLC studies for the formation of the glucuronide conjugate of AHBBP at the 3-OH group rather than at the 2-NH2 group. All the results have been validated using reference 3-HOB and AHBBP.

High performance liquid chromatography with ultraviolet detection used for laboratory routine determination of fluvoxamine in human plasma.

Fluvoxamine is an antidepressant drug introduced into the clinic in 1986. It acts by selectively inhibiting neuronal serotonin recapture. It can be quantified by several methods, including high performance liquid chromatography. The HPLC method used so far needs special equipment and has poor sensitivity. The technique is difficult and time consuming. An easier, quicker and more sensitive HPLC assay for the routine determination of fluvoxamine in human plasma has therefore been developed. After alkalinisation and direct extraction by a mixture of n-hexane-isoamylic alcohol 985: 15 (v/v) of plasma samples, the organic phases were further extracted by HCl 0.1 N. Thirty microL of the final extract (with loxapine as internal standard) were injected directly into a C-8 column with a mobile phase consisting of 370 mL acetonitrile, 0.4 mL diethylamine, 630 mL of distilled water, 25 mL pic B5. UV detection at 254 nm was used. The whole process was completed in 40 min. The detection limit was 10 ng mL-1. No interference was found either with several benzodiazepines or with antidepressant drugs commonly associated during treatments.

Comparative study of interaction mode of diazepines with human serum albumin and alpha 1-acid glycoprotein.

The binding of nine diazepines to human serum albumin (HSA) and to alpha 1-acid glycoprotein (AGP) was investigated by means of fluorescence and circular dichroism (CD) spectroscopies. The binding parameters of diazepam obtained from fluorescence agreed with those obtained from CD measurements. Diazepines have one tight binding site on both HSA and AGP. The binding parameters (nK) of the diazepine: HSA systems are slightly higher than those of diazepine:AGP systems. The relationship between the binding parameters for these two serum proteins and the physicochemical parameters of diazepines was studied by multiple regression analysis to elucidate the binding mode. Moreover, the effects of long-chain fatty acids and cesium chloride on the binding of diazepines to HSA and AGP were also studied. The driving force for the binding of diazepines to both proteins appears to be hydrophobic interaction. In addition, steric effects and electrostatic interactions may also contribute to the binding of diazepines to HSA and AGP, respectively.

Determination of bromazepam in plasma and of its main metabolites in urine by reversed-phase high-performance liquid chromatography.

A high-performance liquid chromatographic method for the determination of bromazepam in plasma and of its main metabolites in urine is described. The unchanged drug is extracted from plasma with dichloromethane, using Extrelut 1 extraction tubes. The residue from this extract is subsequently analysed by reversed-phase high-performance liquid chromatography with ultraviolet detection (230 nm). The limit of detection is 6 ng/ml of plasma, using a 1-ml specimen. For the determination of the metabolites, the urine samples are incubated to effect enzymatic deconjugation and are then extracted with dichloromethane. Following two clean-up steps (back extractions), the final residue is analysed on the same reversed-phase system as the plasma samples. The limit of detection for the two metabolites is 200 ng/ml.

Rebound anxiety in anxious patients after abrupt withdrawal of benzodiazepine treatment.

In this double-blind, placebo-controlled study of 4 weeks of benzodiazepine treatment followed by 3 weeks of abrupt or gradual drug withdrawal, 16 patients whose benzodiazepine was withdrawn abruptly were worse (p less than .05) than 13 who had received placebo in terms of change in mean anxiety scores from the pretreatment level. The scores of seven patients (44%) whose benzodiazepine was withdrawn abruptly increased 10% or more on both the Hamilton Rating Scale for Anxiety and the Self Rating Symptom Scale. There were no cases of rebound anxiety in 14 patients whose benzodiazepine was withdrawn gradually; fewer cases of rebound anxiety were seen with a benzodiazepine that had a long half-life.

Pharmacokinetics of benzodiazepines: metabolic pathways and plasma level profiles.

Large differences exist among the various benzodiazepines with regard to their pharmacokinetic properties and metabolism in man. Some are eliminated from the body at a relatively slow rate, e.g. desmethyldiazepam, and others are metabolized rapidly, e.g. midazolam, triazolam. Several benzodiazepines have major active metabolites that are slowly eliminated, e.g. medazepam, halazepam , quazepam and, consequently, should be considered as potentially long-acting. Such differences may be very important clinically because pharmacokinetic data will help to optimize drug therapy with respect to the choice of the proper drug and drug preparation, as well as with the choice of a proper dose and dosage regimen. The therapeutic objectives of drug therapy differ quite considerably for the various clinical indications of benzodiazepines. In anti-anxiety and anti-epileptic therapy, prolonged or continuous treatment is pursued, so that compounds with relatively long or intermediate elimination half-lives of parent drug or active metabolites are of advantage. In hypnotic treatment, on the other hand, the duration of drug action should be restricted to the duration of the night, hence a compound with a short elimination half-life may be preferred. An overview is given of the pharmacokinetics of the major benzodiazepines currently available and of some interesting new ones that are still in the development stage.

Bioavailability of bromazepam in man after single administration of an oral solution.

The relative bioavailability of a liquid oral form of 7-bromo-1,3-dihydro-5-(2-pyridyl)-2H-1,4-benzodiazepin-2-one (bromazepam, Lexotan, Lexotanil) in comparison with the conventional oral form (capsules) was investigated. The study was performed on six healthy volunteers who were administered both the drug products in a single oral dose of 3 mg of bromazepam in a randomized cross-over trial. An additional investigation was performed on the same subjects by administering the liquid oral solution at a lower dosage: 1.5 mg in order to confirm first-order kinetics at low dosage, too. The results showed the same bioavailability for the oral forms tested and confirmed first-order kinetics for the 1.5 mg dose, too.

[Comparative studies on biologic availability and pharmacokinetics of bromazepam in tablets]. / Vergleichende Untersuchungen zur Bioverfügbarkeit und Pharmakokinetik von Bromazepam aus Tabletten.

Ten male volunteers participated in a randomized crossover trial to compare the bioavailability of bromazepam (7-bromo-1,3-dihydro-5-(2-pyridyl)-2H-1,4-benzodiazepin-2-one) from two different preparations (Normoc, the test preparation, and a commercially available standard preparation). A single dose of 6 mg bromazepam was given. There was no difference in the USP XX rotating basket dissolution test between both preparations. The pharmacokinetic parameters elimination half-life, maximum plasma concentration and area under the curve were not significantly different. With the test preparation, however, smaller interindividual differences were seen. Only the time to peak plasma concentration showed a statistically significant difference. The test preparation yielded a flatter and smoother plasma bromazepam concentration curve compared with the standard preparation. This seems favourable in the case of subchronic dosing with regard to side effects, e.g. sedation.

Studies on metabolism of bromazepam. VI. Reduction of 2-(2-amino-5-bromobenzoyl)pyridine, a metabolite of bromazepam, in the rabbit, rat, and guinea pig.

Three urinary metabolites that were formed by cleavage of the benzodiazepine ring of bromazepam, 2-(2-amino-5-bromobenzoyl)pyridine (ABBP), 2-(2-amino-5-bromo-3-hydroxybenzoyl)pyridine (3-OH-ABBP), and 2-amino-5-bromo-2'-azabenzhydrol (ABAB), were measured in urine of rabbits, rats, and guinea pigs. The major metabolite was 3-OH-ABBP in all animals given bromazepam orally. ABAB was also excreted in major amounts in the guinea pig, but was excreted in minor amounts in the rabbit and rat. Moreover, ABAB was excreted in the urine of all animals given ABBP orally. It may be concluded that ABAB was formed by reduction of the carbonyl group of ABBP. ABBP reduction was catalyzed by NADPH-dependent enzymes occurring in rabbit liver cytoplasm, and rat liver microsomes, and guinea pig liver cytoplasm and microsomes. The reductases were inhibited by sulfhydryl group reagents. The optimum pH of the cytoplasmic enzyme ranged from 7.2 to 7.8, and that of the microsomal enzyme was 6.5. The apparent KM value for the reduction of ABBP by guinea pig liver microsomes was the lowest among all of the liver preparations.

A new metabolic pathway of bromazepam involving attachment of a methylthio group.

1. The structures of three hitherto unidentified metabolites of bromazepam in the rat were elucidated using u.v., mass, n.m.r. and i.r. spectrometry. 2. All three metabolites contained a methylthio or corresponding oxidized group at the C-6' position of the pyridyl moiety. 3. Quantitative analysis of the metabolites determined after administration of [14C]bromazepam to rat revealed that the three metabolites together comprised about 6% of the total radioactivity excreted in the 24-h urine, or about 1% of the dose.