Enantioselective recognition of 2,3-benzodiazepin-4-one derivatives with anticonvulsant activity on several polysaccharide chiral stationary phases

The retention behaviour of racemic 1-(4-aminophenyl)-1,2,3,5-tetrahydro-7,8-methylendioxy-4H-2,3-benzodiazepin-4-one derivatives with anticonvulsant activity on several chiral stationary phases was investigated. The selective performances of six polysaccharide phases, namely, Chiralcel OA, OD, OF, OG, OJ and Chiralpak AD were studied and normal phase HPLC methods were optimized to separate the enantiomeric forms of this class of compounds. The chiral recognition mechanism between the analytes and the chiral selectors was discussed. A molecular modeling study was carried out with the aim to explore the enantioselective molecular recognition process with the Chiralcel OG stationary phase.

Direct liquid chromatography determination of the reactive imine SJG-136 (NSC 694501)

SJG-136 (NSC 694501), 8,8'-[[(propane-1,3-diyl)dioxy]bis[(11aS)-7-methoxy-2-methylidene-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one], which is being developed as a DNA-interactive antitumor agent, contains highly reactive imines in the diazepinone portions of the molecule. Water or alcohol adds readily to the imino moiety to form the corresponding carbinolamine or its alkyl ether, respectively. This sensitivity to protic substances poses a formidable challenge to the formulation and HPLC assay development for the compound. After studying the solution chemistry of SJG-136 and its potential interaction with various stationary phases, two reversed-phase liquid chromatographic assays for the compound have been developed. A direct assay that separates SJG-136 from its water or methanol adducts and an indirect assay that quantifies SJG-136 as its dihydrate adduct are reported. The latter method, which is more practical for drug development, has been validated. It is reproducible (R.S.D.<2%), linear (r2=0.9999) and accurate (within 98-102% recovery), with a lower detection limit of 2.5 ng.

Separation of oxazepam, lorazepam, and temazepam enantiomers by HPLC on a derivatized cyclodextrin-bonded phase: application to the determination of oxazepam in plasma

The enantioselective high-performance liquid chromatography (HPLC) of three racemic 3-hydroxybenzodiazepines, oxazepam (Oxa), lorazepam (Lor), and temazepam (Tem), is a difficult operation because of the spontaneous chiral inversion in polar solvent. To solve this problem, we have developed an HPLC method based on a chiral Cyclobond I-2000 RSP column, maintained at 12 degrees C, and a reversed mobile phase (acetonitrile in 1% triethylamine acetate buffer, TEAA) at a flow rate of 0.4 ml/min. Peaks were detected by a photodiode-array detector at 230 nm for quantification and by an optical rotation detector for identification of (+) and (-) enantiomers. The results showed that peak resolutions of Oxa, Lor, and Tem enantiomers, analyzed under the same conditions, were 3.2, 2.0, and 1.8, respectively. For the determination of Oxa enantiomers in plasma of rabbits, extraction with diethyl ether at pH 1.5, a polar organic mobile phase, and a Cyclobond I-2000 SP column were used. Other analytical conditions were the same as previously described. Blood samples were immediately cooled at 4 degrees C and centrifuged at 0 degrees C for the collection of plasma. The results showed a difference in plasma S(+)- and R(-)-oxazepam concentrations in rabbits. No racemization of S(+)- or R(-)-Oxa enantiomers, added alone to blank plasma, was observed after extraction and enantioselective HPLC analysis.

Solid-phase extraction and liquid chromatographic quantitation of the antiarrhythmic drug L-768673 in a microemulsion formulation

A sensitive and specific method based in solid-phase extraction and reverse-phase liquid chromatography was developed and validated for the quantitation of L-768673 in a microemulsion formulation. Following a water wash, the drug was eluted from the extraction column with acetonitrile and was analyzed on a reverse-phase C18 column with UV detection at 245 nm. The mobile phase consisted of acetonitrile-0.2% trifluoroacetic acid, 0.1% triethylamine (53:47 v/v). The retention time L-768673 was approximately 28 min with a flow rate of 1.5 ml min-1.

Two cellular and subcellular locations for the peripheral-type benzodiazepine receptor in rat liver

Determination of ligand binding properties of the peripheral benzodiazepine receptor (PBBS) in liver, in hepatocytes, and in nonparenchymal cells demonstrated the presence of receptor-specific high-affinity binding in both hepatocyte and nonhepatocyte cells. Density gradient centrifugation showed that the high-affinity receptor in hepatocytes was localised to mitochondria, whereas in nonhepatocytes it was not mitochondrial, but with a possible biliary epithelial cell plasma-membrane location. Both receptors showed the peripheral-type specific high-affinity binding of PK 11195 and Ro5 4864 and could be photolabelled as 18 kDa proteins with [3H]PK 14105. Immunocytochemistry showed the presence of acyl-CoA binding protein, a putative endogenous ligand for the receptor, in both cell locations. Some other properties of the PBBS were investigated in liver. Diphosphatidyl glycerol had a strong inhibitory effect on receptor binding in both liver and adrenal, with Ro5 4864 more sensitive to inhibition than PK 11195. However, whereas soybean lipid and phosphatidyl serine increased the binding of both ligands to adrenal receptor, these lipids had no effect on liver, suggesting that liver PBBS may differ from the well-characterised adrenal PBBS in some of its protein conformation. Modulators of mitochondrial respiration that also influence intermembrane contact site formation were found to elicit no marked stimulatory or inhibitory effects on PBBS ligand binding in liver, a result also found for adrenal mitochondria, suggesting that the extent of contact site formation does not influence ligand binding and that the hepatocyte receptor may not play a role in regulating mitochondrial respiration. These two cellular and subcellular locations of the PBBS in liver and the different effect of phospholipids compared to other peripheral tissues may be important for the role(s) of PBBS in liver and also for the multiple roles ascribed to the receptor and to peripheral-type benzodiazepine ligands.

Autoxidation of drugs: prediction of degradation impurities from results of reaction with radical chain initiators

In the study of the degradation of drug substances by molecular oxygen, their specific reaction mechanisms must be taken into account. The rate-determining step is usually the reaction of the substrate with a radical chain initiator, which is often an unknown impurity. The reactivity and selectivity of autoxidation can be controlled better by using a radical chain initiator, such as AIBN, than by changing the temperature or the oxygen pressure. In this paper the products profiles of four pharmaceutical substances in a simple oxidation test with AIBN are compared with the results of long term natural stability tests or with already established stabilities.

[The effect of pharmaceutic aids on gidazepam biotransformation and bioavailability]

When gidazepam was administered to rats in combination with 4% solutions of Tween 80 or polyvinylpyrrolidone, its bioavailability was higher than its combination with 4% polyethylene glycol 400 solution, as shown by high performance liquid chromatography. Increasing the quantities of these high-molecular compounds in gidazepam solutions was demonstrated to enhance gidazepam dealkylation in the animals after oral administration.

[An experimental study of the pharmacokinetic mechanisms for the development of gidazepam tolerance]

It has been shown that the basis for the development of tolerance to the myorelaxant effect of gidazepam given long to rats is biotransformational changes followed by varying pharmacokinetic parameters: decreases in the AUC of gidazepam and its desalkyl metabolite in plasma, in brain in particular, redistribution of these substances between the plasma and brain of tolerant rats. Changes in pharmacokinetic parameters have no influence on their anxiolytic effects.

Determination of midazolam and its alpha-hydroxy metabolite in human plasma and urine by high-performance liquid chromatography

We describe a new high-performance liquid chromatography (HPLC) method for measurement of midazolam and its major metabolite, alpha-hydroxymidazolam, in clinical samples. Plasma or urine was mixed with 100 ng internal standard Ro 05-6669 and borate buffer, 0.1 M, pH 9. Midazolam and its related compounds were extracted into diethylether. The organic phase was evaporated to dryness. The residue was dissolved in HPLC mobile phase [methanol-isopropyl alcohol-perchloric acid, 0.5 microM (57:25:18)] and injected into the chromatograph. The separation of substances was performed on an Spherisorb S5CN 250 x 4.6 mm HPLC column maintained at 45 degrees C. The detection was performed by absorption measurement at 245 nm. At a flow rate of 1.7 ml/min, the retention times of Ro 05-6669, 1,4 dihydroxymidazolam, alpha-hydroxymidazolam, 4-hydroxymidazolam and midazolam were 4.0, 6.7, 7.8, 9.6, and 10.8 min, respectively. In the concentration range of 5-1,000 ng/ml, the calibration graphs for both compounds were linear. The coefficients of variation of the between-day and within-day assay were < 14% for the concentration range 5-10 and < 7% for the range 10-600 ng/ml. The limits of detection for midazolam and alpha-hydroxymidazolam were 2 and 4 ng/ml, respectively. This assay is more sensitive than earlier methods; it is simple and rapid, and it enables the quantification of midazolam and its alpha-hydroxy metabolite with very good precision and accuracy in human plasma and urine.

Overpressured layer chromatographic study of retention behaviour of various benzodiazepine derivatives on layers impregnated with tricaprylmethylammonium chloride

The retention behaviour of various benzodiazepine derivatives was investigated on silica gel layers impregnated with tricaprylmethylammonium chloride (TCMA). The chromatograms were developed by means of overpressured layer chromatography (OPLC). As for the case of amino- and nitrosalicylic acids, pyrimidine derivatives, barbiturates, penicillins, cephalosporins and tetracyclines, the retention of benzodiazepine derivatives increased with increasing layer TCMA concentration with eluents containing methanol and water, but not TCMA. On increase of the methanol content of the eluent, a retention-decreasing effect was observed. On layers impregnated with TCMA, a linear relationship existed between the RM values of the benzodiazepines and the methanol content of the eluent. A similar relationship held for silica gel layers impregnated with paraffin oil (traditional reversed-phase). There was no correlation between the results obtained on layers treated with TCMA or with paraffin oil. On TCMA-impregnated layers, the retention of compounds having different chemical structures showed no dependence on the pH of the eluent. There were two reasons for this. Firstly, as it was established, above a certain RF value, the pH of the layer in the presence of TCMA was almost identical irrespective of the original pH of the buffer. Secondly, below this RF value, the actual pH of the layer did not have a strong enough effect to cause appreciable differences between the retentions of the dissociated and undissociated species of the analytes. The conditions for optimum separation are given.

Benzodiazepines inhibit temperature-dependent L-[125I]triiodothyronine accumulation into human liver, human neuroblast, and rat pituitary cell lines

L-T3 (T3) accumulates into cells in a temperature-dependent saturable manner through a purported iodothyronine membrane carrier protein. We report energy-dependent uptake of picomolar [125I]T3 into differentiated cell lines derived from human liver, human neuroblast, and rat pituitary malignancies. Furthermore, this cellular uptake is inhibited by classical and nonclassical benzodiazepine-type drugs (BZs); the apparent half-maximal inhibitory concentrations range from 50 nM to 50 microM, varying with drug and cell type. The site of this T3-BZ interaction was explored with cross-competitive radioligand binding to rat liver cell fractions. No interaction was seen in experiments cross-competing unlabeled T3 (10(-9)-10(-5) M) against [3H]Ro5 4864, a peripheral BZ receptor ligand, for binding sites in a crude rat liver mitochondrial fraction. As well, lormetazepam and triazolam, BZs that potently inhibit cellular uptake of [125I]T3, have no effect on [125I]T3 binding to rat liver nuclear sites. Studies of [3H]diazepam and [3H]Ro5 4864 show very little temperature-dependent uptake into HepG2 cells (less than 0.5% over 90 min) and no effect from coincubation of unlabeled T3 (1 microM). Thus, the possibility that BZs are substrates for the T3 carrier protein and are causing the reduced cellular hormonal accumulation via competitive uptake and dilution of the radiolabeled cellular T3 is unlikely. In summary, 1) drugs from the BZ class inhibit high affinity temperature-dependent cellular accumulation of thyroid hormone into cell lines from rat and human species; 2) the site of action of BZ inhibition does not involve direct antagonism of the T3 nuclear receptor, nor is it likely that the peripheral BZ receptor is the iodothyronine carrier. BZs could be interacting with the purported iodothyronine carrier protein itself to block uptake.

Monitoring of concentrations of clobazam and norclobazam in serum and saliva of children with epilepsy

Clobazam was added to the previous antiepileptic drug therapy of 90 children suffering from drug resistant epilepsy. Ten patients became seizure free, although four of these later developed tolerance. Thirty-three patients experienced a decrease in seizure frequency, and 24 of these, too, developed tolerance. Forty-four patients showed no change in seizure frequency, and three experienced an increase. The best results were experienced by patients with myoclonic seizures, whereas patients with complex partial seizures usually developed tolerance. The concentrations of clobazam and its active metabolite norclobazam were measured in 251 serum and 57 saliva samples. The group of seizure-free patients had the lowest clobazam and norclobazam concentrations; tolerance was associated with the highest concentrations. Beneficial side effects were associated with low, and adverse effects with high, concentrations of norclobazam. The concentrations of clobazam and norclobazam in saliva correlated with concentrations in serum. Monitoring of serum and salivary concentrations of clobazam and norclobazam is of limited value only, and no therapeutic target range can be given.

New pyrrolobenzodiazepine antibiotics, RK-1441A and B. II. Isolation and structure

Antibacteriophage antibiotics, RK-1441A and B, related to neothramycin were isolated from the culture broth of Streptomyces sp. and their structures were deduced from spectroscopic analyses. The structure of RK-1441A was 8,11-dihydroxy-3,7-dimethoxy-5-oxo-1H-pyrrolo[2,1-c:1,4]benzodiazepine. RK-1441B is a tautomeric mixture at C-3 of the structure, 3,8,11-trihydroxy-7-methoxy-5-oxo-1H-pyrrolo[2,1-c:1,4]benzodiazepine.

[Drug analysis with polarographic methods. 33. Electroanalytic studies of a new benzodiazepine: [6(o-chlorophenyl)-2,4-dihydro-2-[(4-methyl-1-piperazinyl) methylene]-8-nitro-1H-imidazol[1,2-a][1,4]benzodiazepine-1-one (WHO) (loprazolam,1)] and content determination its drug forms]

Loprazolam (1) is a tricyclic benzodiazepine containing a new butazadiene moiety, which has not been investigated by polarography up to now. 1 is reduced in three waves at a DME over the whole pH-region. In BRP (pH 2-9) 10 electrons are consumed in this process. The first step is suitable for the determination of 1 in Loprazolam tablets containing 1 or 2 mg. These tablets are on the pharmaceutical market in several European countries. The mechanism of the electrode process will be reported in the communication XXXIV.

Structure of 9-chloro-7-(2-chlorophenyl)-3,5-dihydro-[1,2,4] triazino[4,3-a][1,4]benzodiazepin-2(1H)-one

C17H12Cl2N4O, Mr = 359.2, triclinic, P1-, a = 8.777 (8), b = 12.715 (4), c = 14.883 (4) A, alpha = 95.69 (2), beta = 83.62 (3), gamma = 93.46 (3) degrees, V = 1640.5 A3, Z = 4, Dx = 1.454 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 3.99 cm-1, F(000) = 736, T = 293 K, R = 0.039 for 2783 observed reflections. The seven-membered heterocyclic ring has a cycloheptatriene-like boat conformation with bow and stern angles 60.5 (8) and 33.8 (8) degrees, and 59.8 (8) and 35.9 (8) degrees, respectively, in the two independent molecules. The triazino ring is near planar in both molecules. The angles between the 7-phenyl ring and the fused benzo moiety are 88.9 (8) and 82.0 (8) degrees. Corresponding bond lengths and angles in the two molecules are generally similar and agree well with accepted values.

Study of the interaction of clobazam with cyclodextrins in solution and in the solid state

Inclusion complexes of clobazam with alpha-, beta-, gamma-cyclodextrins (CyDs) and heptakis(2.6-di-O-methyl)-beta-cyclodextrin (DM-beta-CyD) in aqueous solution and in the solid phase were studied by the solubility method, infrared (IR) spectroscopy, differential scanning calorimetry (DSC), and X-ray diffractometry. In addition, inclusion complex of clobazam with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and the solid dispersion of clobazam with methyl cellulose (MC) in a ground mixture were investigated by IR, DSC and X-ray diffractometry. It was observed that DM-beta-CyD had the highest stability constant among the four CyDs in solution. Thermal and X-ray diffraction analyses showed that clobazam molecules existed in a molecularly dispersed state in the ground mixture of CyDs. Infrared spectra showed lower frequency shifts in the case of the ground mixtures of clobazam with natural CyDs, which can be attributed to the formation of hydrogen bonds between the two carbonyl groups of clobazam and hydroxyl groups of natural CyDs. In contrast, higher frequency shifts were observed in the case of the ground mixtures of clobazam with methylated CyDs and MC and these were considered to be due to the monomolecular dispersion of clobazam in a hydrophobic environment. The mode of interaction of clobazam with DM-beta-CyD was different from that with natural CyDs in the ground mixtures. Furthermore, the crystalline inclusion complex of clobazam with DM-beta-CyD was obtained by heating of the coprecipitate in vacuo at 120 degrees C for 1 h.

Pinazepam: analytical study of synthesis, degradation, potential impurities

Pinazepam specifications are presented, synthesis method and quality control in the course of the synthesis on the starting materials, intermediate products and solvents are described. The used analytical methods of studied potential impurities, both from the synthesis and from degradation under exceptional conditions, are summarized and their validation is done. At last the Pinazepam satisfactory big stability is shown.

HPLC method for simultaneous determination of clobazam and N-desmethylclobazam in human serum, rat serum and rat brain homogenates

A method for simultaneous determination of clobazam (CBZ) and its active metabolite N-desmethylclobazam (DCBZ) in various biological samples by RP-HPLC with UV detection is described. The determination of both CBZ and DCBZ is performed without derivatization. The internal standard is diazepam. The method is rapid and simple with sensitivity limits of 10 ng/mL for both CBZ and DCBZ and is suitable for routine analysis as well as for animal studies.

[Biotransformation of the 14C-hydrogenated analog of phenazepam in inbred mice]

The elimination of 14C-hydrogenated analogue of phenazepam and its metabolites was studied in inbred C57B1/6 (B/6), BALB-c (C) and CBA mice. The kinetics of two-phase elimination of 14C-compounds with urine and feces was similar in all the above mouse strains. The excretion was realized mainly with feces, exceeding elimination with urine 5-6-fold in B6 mice and 10-11-fold in C and CBA mice. Some interstrain quantitative differences in metabolite composition were found. No metabolite was detected whose concentration would indicate a predominating direction of biotransformation of 14C-hydrogenated phenazepam analogue or distinguish it from other mouse strains. In the organism of mice, 14C-hydrogenated phenazepam analogue undergoes active aromatic hydroxylation and methoxylation via heterocycle (and possibly via chlorine-containing ring). At the same time dehydrogenation of 14C-hydrogenated phenazepam analogue molecule was not recorded.

Placental transfer of quazepam in mice

The disposition of 14C-quazepam following a single 5-mg/kg po dose was studied at the postembryonic period (day 12 of pregnancy) and near-term (day 18 of pregnancy). In both 12- and 18-day pregnant mice, radioactivity from the quazepam dose was widely distributed in the maternal tissues, with the highest levels in the liver and kidneys. At the time points analyzed (1, 5, and 24 hr post-dose), radioactivity levels in the fetus were consistently 44% of the maternal plasma levels in 12-day pregnant mice. In 18-day pregnant mice, fetal radioactivity levels at these time points were consistently equal to or slightly greater than maternal plasma levels. This indicates that radioactivity was taken up and eliminated from fetal tissues at rates that were reasonably similar to those in corresponding maternal tissues. No accumulation of radioactivity was observed in the fetus or in maternal tissues in either the 12-day or the 18-day pregnant mice. In 18-day pregnant mice, concentrations of quazepam and its metabolites were measured either by gas-liquid chromatography or thin layer radiochromatography. In the maternal plasma, concentrations of quazepam, its first-formed metabolite, 2-oxoquazepam, and 3-hydroxy-2-oxoquazepam were relatively low at all time points; levels of N-desalkyl-2-oxoquazepam and 3-hydroxy-N-desalkyl-2-oxoquazepam (HDOQ) were much higher. Fetal levels of unchanged drug and metabolites were generally less than or equal to maternal plasma levels, except for HDOQ levels, which were higher in the fetus.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of clobazam, N-desmethylclobazam and their hydroxy metabolites in plasma and urine by high-performance liquid chromatography

Owing to the pharmacological and clinical importance of the determination of plasma and urine levels of the hydroxy metabolites of clobazam and N-desmethylclobazam in healthy volunteers and in epileptic patients, a high-performance liquid chromatographic (HPLC) method was developed that permits the determination of all these compounds in the same plasma or urine sample. The method involved ether extraction at pH 13 with diazepam as internal standard for the measurement of clobazam and N-desmethylcobazam, followed by ether extraction at pH 9 with nitrazepam as internal standard for the measurement of the hydroxy derivatives. The limit of detection was about 10-20 ng/ml for each of these compounds. Applications to patients were limited by chromatographic interferences between the hydroxy metabolites and some medications currently associated with clobazam in the treatment of epilepsy. The only interference in clobazam and N-desmethylclobazam analysis was from N-desmethyldiazepam. Despite these inconveniences, this HPLC procedure appears to be the only available method for the simultaneous quantification of clobazam and its three main metabolites.

A new approach for dealing with the stability of drugs in biological fluids

The purpose of this study was to develop a procedure for investigating the stability of drugs in biological fluids based on sound experimental design and to use a statistical procedure which would allow conclusions to be made concerning stability with an acceptable degree of certainty (95%). The experimental procedure involved replicate analysis of the drug in stored and freshly prepared samples on the same day. The relative difference in response between these two sets of samples and a 90% confidence interval for the true change in response was calculated. This confidence interval enabled us to detect a pharmacokinetically relevant degradation. It is argued that this approach is superior to the stability test procedures based on the t test. The application of the method to the assessment of the stability of three different drugs in biological fluids is described.

[Spectral changes in the liver microsomal cytochrome P-450 of rats during interaction with phenazepam and its 3-hydroxy metabolite]

Phenazepam (I) and 3-hydroxymetabolite (II) interacting with cytochrome P-450 of the liver of rats administered phenobarbital and 3-methylcholantrene demonstrated the 2nd type of spectral changes in hemoprotein. The binding constants of I and II considerably differ, which points to the possibility of interaction of substrates with different areas of hemoproteins. The characteristic points (maximum, minimum, isobestic) of the cytochrome P-450 spectrum were displaced during II titration to the longwave region as compared with I. The calculation of electron density on the atoms of the heterocycle and aromatic nuclei of the molecules of I and II has shown that the differences in the spectra of I and II binding with cytochrome P-450 are determined by the distribution of electron density of their heterocycle.

A 1H nmr study of the amide-bond conformational equilibrium in pirenzepine

The hindered rotation about the exocyclic amide bond of pirenzepine has been studied using 1H nuclear magnetic resonance spectroscopy. The ratios of the two slowly interconverting conformations (1:1.76 at 2 degrees C and 1:2.37 at 30 degrees C) and the rate of interconversion (1 +/- 0.5 s-1 at 20 degrees C and 247 +/- 20 s-1 at 80 degrees C with delta g ++80 = 71 KJ mol-1) have been measured at various temperatures. The observed rapid rates of interconversion allow us to eliminate the rate of conformational selection of forms II and III as a major contributor to the slow phase of the binding kinetics observed when pirenzepine binds to muscarinic receptors from rat brain (Stockton, Birdsall, Hulme and Burgen, unpublished results).

Hydrolysis of clonazepam, flunitrazepam and nitrazepam by hydrochloric acid. Identification of some additional products

Several by-products in the hydrochloric acid hydrolysis of clonazepam, flunitrazepam and nitrazepam are isolated by a combination of TLC and HPLC. With mass and NMR spectroscopic methods the structures of the by-products are established. Some indications are given for possible modes of formation of the by-products.

Pharmacokinetic studies on Ro 15-1788, a benzodiazepine receptor ligand, in the brain of the rat

Methods for determining Ro 15-1788 in brain tissue were developed using gas chromatography with nitrogen-phosphorus detection, and using reverse-phase high performance liquid chromatography. Application of the methods to pharmacokinetic studies in the rat found the elimination half-life of Ro 15-1788 from rat brain to be 16 min. Ro 15-1788 was undetectable in rat plasma at the time points studied. Concentrations of Ro 15-1788 in the brain were reduced if chlordiazepoxide was coadministered.

Assay of chlordiazepoxide and demoxepam in chlordiazepoxide formulations by difference spectrophotometry

Rapid difference spectrophotometric methods for chlordiazepoxide and demoxepam in chlordiazepoxide formulations are described which overcome the nonspecificity of the official spectrophotometric assays. The procedures are based on the measurement of the difference absorbance at 269 nm of equimolar solutions of chlordiazepoxide at pH 8 and pH 3 and the difference absorbance at 263 nm of equimolar solutions of demoxepam at pH 13 and pH 8. The methods are specific for chlordiazepoxide and demoxepam in the presence of both compounds, 2-amino-5-chlorobenzophenone, certain coformulated drugs, and formulation excipients. Analyses of commercial dosage forms of chlordiazepoxide have shown the presence of demoxepam at concentrations in excess of the pharmacopoeial specifications in some aged samples.

Conformational analysis of the antiulcer drug pirenzepine. X-ray investigations, molecular mechanics and quantum mechanical calculations and comparisons with structurally or pharmacologically related compounds

The crystal structures of the antiulcer drug 5,11-dihydro-11-[(4-methyl-1-piperazinyl) acetyl]-6H-pyrido[2,3-b] [1,4]benzodiazepin-6-one dihydrochloride (pirenzepine dihydrochloride, L-S 519 CL 2, Gastrozepin) and its monoprotonated form (pirenzepine monohydrochloride, L-S 519 CL) were determined by X-ray analysis. Molecular mechanics (MMPI) and semiempirical quantum chemical (MNDO) calculations showed that the calculated minimum energy conformations of the tricycle and of the exocyclic amide group are in agreement with the crystal structures. The conformational energies of pirenzepine as a function of four important torsional angles were calculated using different semiempirical quantum chemical methods with the CNDO/2 (complete neglect of differential overlap)-, MNDO (modified neglect of diatomic overlap)- and PCILO (perturbative configuration interaction using localized orbitals)-approximations. The conformation of one local energy minimum corresponds closely to the crystal structure of pirenzepine monohydrochloride. This conformation has a spatial arrangement which is analogous to a single consistent conformation known from the literature of 24 anticholinergic agents determined from their crystal structures by a computer graphics analysis. On the other hand there are no structural relationships of any low energy conformation of pirenzepine to conformations of other classes of tricyclic compounds which could rationalize their antidepressant, neuroleptic or antihistaminic activity. This finding explains the absence of any central effect of pirenzepine following intracerebral application. The computational elucidation of the conformational requirements for the interaction with the muscarinic receptors may be helpful for the interpretation of the selectivity of pirenzepine within the muscarinic system.

Methods for the determination of lorazepam and chlordiazepoxide and metabolites in brain tissue. A comparison with plasma concentrations in the rat

Rapid and sensitive methods are described for determining lorazepam and for determining chlordiazepoxide and its metabolites in brain tissue of the rat. Lorazepam was determined by means of solvent extraction and electron-capture gas-liquid chromatography and concentrations as low as 5 ng/g tissue could be measured. High-performance liquid chromatography with UV detection was used to determine chlordiazepoxide and its metabolites and was sensitive to 0.1 micrograms/g tissue. The methods were used to investigate the brain and plasma pharmacokinetics of these compounds in animals that had been chronically treated with lorazepam or chlordiazepoxide. In both experiments brain and plasma levels of all compounds assayed were found to correlate highly.

Quantitative analysis of CM 6912 (ethyl loflazepate) and its metabolites in plasma and urine by chemical ionization gas chromatography mass spectrometry. Application to pharmacokinetic studies in man

A chemical ionization gas chromatographic mass spectrometric assay is described for ethyl loflazepate (CM 6912), a new benzodiazepine with a potent anti-anxiety activity, and two of its metabolites in plasma and urine. The parent drug was separated from the biological samples by simple extraction at pH 9. In all samples analysed, parent drug levels were below the detection limit, confirming its extensive biotransformation at the sites of absorption and during its first pass through the liver. Pharmacokinetic data were obtained by measuring the total levels of two of the major metabolites. Accurate data may not be obtained for both metabolites separately since one of them (M1) is chemically transformed to metabolite M2 during plasma sampling, storage and extraction. Their total levels were measured after complete degradation of the unstable metabolite and extraction of the sample at pH 9. The precision and accuracy of this method are better than 10% in the low ng range. The detection limit is 1 ng ml-1. Pharmacokinetic data were obtained from human volunteers given a single oral dose of 2 mg CM 6912 in tablet form. Cp max values ranged from 30 to 55 ng ml-1 and were reached within 1.5 to 3 h after administration. Following the achievement of peak levels the concentration declined with an apparent biexponential pattern showing an elimination half-life ranging from 51 to 103 hours in its terminal phase.

Methane negative chemical ionization analysis of 1,3-dihydro-5-phenyl-1,4-benzodiazepin-2-ones

The methane negative chemical ionization (NCI) mass spectra of the medically important 1,3-dihydro-5-phenyl-1,4-benzodiazepin-2-ones generally consisted solely of M- and (M-H)- ions. Attempts to find the location of the H lost in the generation of the (M-H)- ion were unsuccessful, although many possibilities were eliminated. A Hammett correlation analysis of the relative sensitivities of a series of 7-substituted benzodiazepines suggested that the initial ionization takes place at the 4,5-imine bond. For certain benzodiazepines, the (M-H)- ion generated by methane NCI was 20 times more intense than the MH+ ion generated by methane positive chemical ionization (PCI). By using NCI, a sensitive and simple GC-MS assay for nordiazepam was developed that can quantitate this important metabolite of many of the clinically used benzodiazepines in the blood and brain of rats.

Determination of clonazepam in tablets by dc polarography

A simple and convenient method for the routine determination of clonazepam in tablets by dc polarography is described. Clonazepam is extracted from the sample by ethanol and diluted with pH 4.15 acetate buffer in a volumetric flask. The filtered solution is then polarographed at the dropping mercury electrode versus the saturated calomel electrode. The polarographic wave is well developed; the determination is quantitative, precise, and accurate.

High-performance liquid chromatographic determination of chlordiazepoxide and major related impurities in pharmaceuticals

A rapid, precise, forward-phase (adsorption) high-performance liquid chromatographic procedure is presented for the determination of chlordiazepoxide and two common impurities, 7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide and 2-amino-5-chlorobenzophenone, in commercial formulations and for the determination of the benzophenone in the chlordiazepoxide drug substance. The method involves simultaneous quantitation of chlordiazepoxide and the 1,3-dihhydro impurity, followed by quantitation of the benzophenone from a separate sample extract using a second mobile phase. A single microparticulate silica gel column is used throughout. Nitrazepam and o-dinitrobenzene are the internal standards, Quantitation is by peak area using a computing integrator, except that the peak due to the benzophenone is quantitated by peak height. The described procedure is of equivalent precision, but superior accuracy, to the BP 1973 spectrophotometric procedure for the analysis of chlordiazepoxide in chlordiazepoxide formulations. Quantitation of the 1,3-dihydro and the benzophenone impurities at levels as low as 6.3 and 0.9 ng, respectively, is demonstrated.

Determination of 7-iodo-1,3-dihydro-1-methyl-5(2'-fluorophenyl)-2h-1,4-benzodiazepin-2-one (Ro 7-9957) and its major biotransformation products in blood and urine by electron capture-gas-liquid chromatography

A sensitive and specific electron capture-gas chromatographic assay was developed for the determination of 7-iodo-1,3-dihydro-1-methyl-5(2'-fluorophenyl)-2H-1,4-benzodiazepin-2-one (I) and its major metabolites in blood and urine. The overall recovery of I and its N-desmethyl metabolite (II) from blood is apparently quantitative. The recovery of the major urinary metabolite, the N-desmethyl-3-hydroxy analog (IV), and the minor metabolites, the N-desmethyl analog (II) and the N-methyl-3-hydroxy analog (III) added to urine as authentic reference standards ranged from 80 to 85%. The sensitivity limits of detection are of the order of 2-3 ng of I and 4-5 ng of II per ml of blood or urine. The method was applied to the determination of blood levels and the urinary excretion pattern in a dog following oral and intravenous administration of a 1-mg/kg dose (total 13 mg), and in man following the intravenous administration of single 5- and 10-mg doses. The N-desmethyl metabolite II was more predominant in dog blood than was the orally or intravenously administered I, but II was barely measurable in human blood.

Determination of major impurity in chlordiazepoxide formulations and drug substance

Procedures for quantitating the lactam impurity, 7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide, which can be present in chlordiazepoxide formulations, is presented. The method consists of trapping chlordiazepoxide in sulfuric acid in kieselguhr, eluting the impurity with ether, and quantitating by UV spectrophotometry in absolute alcohol at 312 nm.