[Investigations of poisonings with benzodiazepine derivatives mixtures by thin-layer chromatography]

The thin-layer chromatography method was proposed for separation and identification of drugs in mixture alprazolam : brotizolam : clorazepate dipotassium. The mixture of these drugs excreted from body fluid (blood) was investigated by the thin-layer chromatography. Most acceptable is this mobile phase : benzene : dioxane : conc. ammonia : methanol : ethanol (60:25:5:10:10). Rf values for drugs: alprazolam 0.81-0.83, brotizolam 0.59-0.62, clorazepate dipotassium 0.67-0.69.

Comparison of patient questionnaires, medical records, and plasma assays in assessing exposure to benzodiazepines in elderly subjects

OBJECTIVE

Exposure in pharmacoepidemiologic studies can rely on various sources such as medical records, patient questionnaires, or plasma samples, which do not always concur. This study endeavored to compare sources of information on current exposure to benzodiazepines in elderly subjects.

METHODS

In a study in a hospital admissions department, 1136 elderly subjects included in a case-control study each completed a structured questionnaire. In addition, an inspection of the medical records of each subject was performed, as well as screening of a plasma sample (high-pressure liquid chromatography--diode array detector) for current exposure to benzodiazepines.

RESULTS

Benzodiazepines were found in the plasma of 33% of 1013 patients, in the records of 31% of patients, and in the questionnaires of 36% of 797 respondents. With use of the plasma results as a standard, questionnaires had 11% false positives and 28% false negatives; medical records had 14% false positives and 23% false negatives. The kappa for concordance between questionnaires and records was 0.63. Most of the errors were related to the unexpected presence in plasma of clorazepate, commonly used as a hypnotic agent.

CONCLUSIONS

Patient recall and medical records are not reliable measures of current exposure to benzodiazepines in elderly persons, although this unreliability may be more marked with certain drugs used as hypnotic agents.

Effects of a 44-day administration of phenobarbital on disposition of clorazepate in dogs

The disposition of clorazepate, a benzodiazepine anticonvulsant, was determined in dogs after administration of a single oral dose of clorazepate (2 mg/kg of body weight) and after oral administration of clorazepate (2 mg/kg, q 12 h) concurrently with phenobarbital (5 mg/kg, q 12 h) for 44 consecutive days. Serum concentrations of nordiazepam, the active metabolite of clorazepate, were measured. After a single oral dose of clorazepate, maximal nordiazepam concentrations ranged from 569.6 to 1,387.9 ng/ml (mean, 880.2 +/- 248.9 ng/ml) and were detected 16.8 to 131.4 minutes (mean, 85.2 +/- 36 minutes) after dosing. After administration of phenobarbital for 44 consecutive days, maximal nordiazepam concentrations were significantly (P < 0.01) lower, ranging from 209.6 to 698.5 ng/ml (mean, 399.3 +/- 155.6 ng/ml) at 68.4 to 145.8 minutes (mean, 93 +/- 25.8 minutes) after dosing. Mean area under the curve (AUC) on day 1 (mean, 3.37 +/- 0.598 ng.min/ml) was significantly (P < 0.001) greater than AUC on day 44 (1.66 +/- 0.308 ng.min/ml). Oral clearance was significantly (P < 0.01) greater on day 44 (12.44 +/- 2.55 ml/min/kg), compared with that on day 1 (6.16 +/- 1.35 ml/min/kg). Values for area under the first moment curve, oral volume of distribution, mean residence time, and elimination half-life were not significantly altered by concurrent administration of phenobarbital. Administration of phenobarbital altered the disposition of clorazepate such that the amount of nordiazepam in circulation during each dose interval was significantly reduced. Adequate control of seizures in epileptic dogs, therefore, may require higher dosages of clorazepate when it is coadministered with phenobarbital.

Clorazepate, correlation between metabolism and anticonvulsant activity

The metabolism and the anticonvulsant effect of clorazepate were followed for 2 h after its i.v. administration to mice. The ED50 of the drug was 12 mg/kg at 1 min against pentetrazole-induced convulsions (45 mg/kg i.v.), it reached a minimum at 1 h (2.0 mg/kg) and rose to 2.7 mg/kg at 2 h. The concentrations of unchanged clorazepate and its metabolites, desmethyldiazepam and oxazepam, were determined in plasma and brain after administration of the respective ED50s. Unchanged clorazepate could be detected in plasma for the first hour but never in brain, so it can be considered as inactive pro-drug. The brain concentrations of desmethyldiazepam and oxazepam after the respective ED50s of clorazepate were considerably higher at 1 and 15 min than after longer time intervals. This may be explained by a time lag needed to reach and bind to the benzodiazepine receptor.

Effect of clorazepate in spasticity and rigidity: a quantitative study of reflexes and plasma concentrations

The effect on increased myotatic reflexes of desmethyldiazepam, formed from its precursor clorazepate, was assessed in a double-blind cross-over study of 27 days duration. Eight patients with spasticity or rigidity were given placebo or active substance; first in loading doses for 2 days, then 5 mg every 12 h for a total of 10 days. A wash-out period of 7 days was interposed between the 2 10-day periods. Desmethyldiazepam had a normalizing effect on the increased phasic ankle reflexes seen in spasticity, but not on the increased tonic reflex seen in rigidity. The mean concentration of desmethyldiazepam in the steady state was 1227 nmol/l (range 600-1990 nmol/l). The plasma concentration of desmethyldiazepam tended to correlate with the percent decrease in phasic reflex activity (P = 0.08, 2-tailed). A slight drowsiness in 2 patients was the only side-effect seen. In conclusion, desmethyldiazepam given as clorazepate seems to be a suitable medicament in the treatment of spasticity.

Plasma concentrations and clinical effects after single oral doses of prazepam, clorazepate, and diazepam

In a double-blind parallel-group pharmacokinetic and pharmacodynamic study, 31 healthy volunteers received single oral doses of prazepam (10 mg), clorazepate (7.5 mg), or diazepam (5 mg). Appearance in plasma of diazepam and of desmethyldiazepam was rapid after administration of diazepam and clorazepate, respectively, with peak plasma concentrations reached within an average of 1 hour. After oral prazepam, however, desmethyldiazepam appeared in blood slowly, with the highest mean concentration at 6 hours postdosage. Clinical self-ratings of fatigue and of "feeling spacey" were significantly different among groups, with changes over baseline being more marked with clorazepate and diazepam than with prazepam. Thus, differences in absorption rate of orally administered benzodiazepines can lead to differences in the intensity of single-dose effects, despite administration of doses that are equivalent in terms of long-term anxiolytic efficacy.

Antiepileptic effect and serum levels of clorazepate on children with refractory seizures

Clorazepate dipotassium is rapidly decarboxylated to yield desmethyl diazepam. The antiepileptic effect of clorazepate was studied in 29 epileptic children with refractory seizures. Their ages were ranged from one year 9 months to 20 years (mean 11 years 6 months). Serum clorazepate levels were also determined in 16 patients. The mean initial dose was 0.91 mg/kg/day, and the dose was increased up to 3 mg/kg/day. Within several days after initiation of clorazepate therapy, a decrease in seizure frequency was seen in patients in whom clorazepate was effective. Excellent results (decrease in seizure frequency by more than 80%) were obtained in 7 patients (24.1%), a moderate improvement with a 50 to 80% decrease was seen in 7 patients (24.1%), and a partial improvement with less than 50% decrease was seen in 7 patients (24.1%). No benefit was seen in 8 patients (27.7%). Serum clorazepate levels in patients with excellent results were 31 to 77 ng/ml (mean 55 ng/ml), those in patients with a moderate improvement were 130 to 225 ng/ml (mean 163 ng/ml), and those in patients with a partial improvement were 142 to 518 ng/ml (mean 273 ng/ml). Serum clorazepate levels in patients with no benefit were 34 to 97 ng/ml (mean 56 ng/ml). There was no direct relationship between serum clorazepate levels and clinical response. The results of this study indicate the efficacy of clorazepate for epileptic children with refractory seizures.

Prolonged accumulation of diazepam in obesity

Six obese (mean weight 92 kg) and five normal (60 kg) subjects received 2 mg diazepam nightly for 30 nights. Determination of diazepam and desmethyldiazepam plasma concentrations during the dosing period and for a withdrawal period indicated that accumulation half-life for both diazepam (7.8 days in obese vs. 3.1 days in normal subjects, P less than 0.05) and desmethyldiazepam (30.3 vs. 7.2 days, P less than 0.05) was markedly prolonged in obese subjects. However, mean steady-state plasma concentrations of diazepam (68 vs. 67 ng/ml) and desmethyldiazepam (156 vs. 91 ng/ml) did not significantly differ between groups. To determine the basis for this delay in accumulation in obese subjects, single-dose pharmacokinetics of diazepam and desmethyldiazepam were determined. Diazepam elimination half-life was greatly prolonged in the obese subjects (82 vs. 32 hours, P less than 0.005), with no change in total metabolic clearance (32 vs. 26 ml/min). Instead, a large increase in volume of distribution (228 vs. 70 liters, P less than 0.01) was the reason for prolongation of the elimination half-life. Similarly for desmethyldiazepam, elimination half-life was prolonged in obese subjects (130 vs. 56 hours, P less than 0.01), without a change in total metabolic clearance (13.7 vs. 19.2 ml/min), due to increased volume of distribution (151 vs. 73 liters, P less than 0.01). During chronic dosing with diazepam, obese patients may experience a much slower onset of maximal drug effect compared to normal-weight patients because of the greatly delayed accumulation of diazepam and desmethyldiazepam.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatography determination of dipotassium clorazepate and its major metabolite nordiazepam in plasma

A rapid and sensitive high-performance liquid chromatographic method is described for the quantitative analysis of dipotassium clorazepate (CZP) and its major metabolite nordiazepam (ND) in fresh human and dog plasma. The method consists of two separate selective ND extractions from a plasma sample without and with conversion of all the CZP to ND. For quantitation, diazepam (DZP) is used as the internal standard. The chromatographic phase utilized in a reversed-phase Hibar EC-RT analytical column prepacked with LiChrosolv RP-18 with a solvent system consisting of acetonitrile-0.05 M sodium acetate buffer, pH 5.0 (45:55). The UV absorbance is monitored at 225 nm using a variable-wavelength detector. The mean assay coefficient of variation over a concentration range of 20-400 ng per ml of plasma is less than 3% for the within-day precision. Recoveries of ND, DZP and CZP (as ND) are essentially quantitative at all levels investigated. The calibration curves of ND are rectilinear (r2 = 0.99) from the lower limit of sensitivity (2 ng/ml) to at least 2000 ng/ml in plasma. Applicability of the method to CZP and ND disposition studies in the anaesthetized mongrel dog is illustrated. When the two separate selective nordiazepam extractions from plasma cannot be performed immediately after blood sampling, an extrapolation kinetic method is suggested for the estimation of CZP concentration. In all previous in vivo studies, CZP has been determined only with gas-liquid chromatographic methods.

Pharmacokinetics of chlorazepate after intravenous and intramuscular administration

Dichlorazepate (DPC) was given to eight healthy volunteers aged 22-38 years (five males and three females). The dose was 20 mg (48.9 mumol) given either as an IV or an IM injection. The interval between the injections was at least 1 week. Plasma samples were analysed for desmethyldiazepam (DMD) by HPLC before and after acid hydrolysis. The kinetics after both IV and IM administration could be explained by a one or two compartment open model. By comparing values before and after hydrolysis an estimate of di- and/or monopotassiumchlorazepate (MPC) could be made. The bioavailability was almost 100% after IM administration. The plasma half lives of DPC and DMD were independent of the form of administration (2.42 and 46.0 h respectively after IV and 2.29 and 45.1 h respectively after IM injection).

[Mnemic disturbances following experimental alcohol-tranquilizer application (author's transl)]

Mnemic disturbances occurred in 8 of 14 subjects during a pharmcopsychological investigation of possible interactions between alcohol and dipotassium chlorazepate (Tranxilium). The blood alcohol concentrations were between 0.87% and 1.32%; the serum concentrations of the active metabolite nordiazepam were in the therapeutic range between 145 ng/ml and 345 ng/ml. The constitutional, dispositional, and situative conditions are presented. The forensic medical interpretation of such mnemic disturbances must be made critically and with reservation when evaluating a psychopathological state.

Monitoring clorazepate dipotassium as desmethyldiazepam in plasma by electron-capture gas--liquid chromatography

We describe a procedure for determing clorazepate dipotassium as its decarboxylated, pharmacologically active metabolite, desmethyldiazepam, in 100 microL of plasma, with use of electron-capture gas--liquid chromatography and with methylnitrazepam as the internal standard. The procedure is a one-tube, one-step extraction without derivative formation and is accurate, reproducible, and rapid. The sensitivity limit is 20 micrograms/L. Within-run and between-run CV's (concentration, 3.5 mg/L) were 2.9 and 3.5%, respectively. Within-run CV's for 1.5 and 1.0 mg/L concentrations were 3.9 and 4.3%, respectively. For a 1.0 mg/kg per day dose of clorazepate dipotassium, the mean steady-state concentration of desmethyldiazepam in plasma was 1.037 mg/L.

Evaluation of clorazepate (Tranxene) as an anticonvulsant--a pilot study

Desmethyldiazepam--providing the long-term anticonvulsant effect when diazepam is given orally--is conveniently administered as clorazepate (Tranxene). In this study, clorazepate was compared to phenobarbital as a secondary anticonvulsant in eight ambulatory, adult outpatients. Stable doses of phenytoin were maintained throughout. Drowsiness was present in all on phenobarbital, but there were no clorazepate-related side effects. Seizure control did not differ for each treatment. Addition of common side effects of phenytoin and phenobarbital limited the attained serum levels of each when used together. Clorazepate doses in the 0.56-mg-per-kilogram range gave desmethyldiazepam levels in the 1.0-microgram-per-milliliter range. Induction of metabolism was suggested by falling desmethyldiazepam levels despite increasing doses. Clorazepate is an effective, nontoxic secondary anticonvulsant.

Effect of antacids on absorption of clorazepate

The effect of a magnesia and alumina antacid suspension on the absorption of clorazepate dipotassium was studied in 15 normal healthy adult subjects who ingested a 15-mg dose of clorazepate alone or with single or multiple doses of antacid. The results of this three-period randomized complete crossover study showed a trend of initially slower absorption and lower peak nordiazepam plasma levels when administered with the antacid suspension. However, there were no significant differences among treatments in the extent of absorption as measured by the area under the plasma level-time curves. Clorazepate plasma levels were of relatively short duration and similar for all treatments. The urinary excretion pattern was likewise comparable with conjugated oxazepam, the major species measured. Plasma elimination half-lives of nordiazepam and clorazepate were not affected by the antacid treatments.

Determination of clorazepate and its major metabolites in blood and urine by electron capture gas-liquid chromatography

A sensitive and specific blood level method employing differential extraction was developed for the determination of clorazepate and its N-desmethyldiazepam metabolite by electron capture gas-liquid chromatography (GLC-ECD). The assay requires the initial extraction of N-desmethyldiazepam, the major metabolite, into benzene-methylene chloride (90:10) from the biological sample made alkaline with 0.1 N NaOH. The samples is then acidified with 2 N HCl to decarboxylate clorazepate to N-desmethyldiazepam, which is then extracted into benzene-methylene chloride (90:10) after adjusting the pH to 12.8 with NaOH. The two extracts are evaporated and the residues are dissolved in benzene which contains griseofulvin as the reference standard. These solutions are assayed by GLC-ECD. The overall recovery and sensitivity limit of the assay for clorazepate is 60+/-5% (S.D.) and 4.0 ng/ml blood, respectively, while that for N-desmethyldiazepam is 95+/-5% (S.D.) and 4.0 ng/ml blood, respectively. The urinary excretion of clorazepate was determined by the measurement of the levels of N-desmethyldiazepam and oxazepam, the major urinary metabolites of clorazepate, both prior to and after enzymatic deconjugation. These methods were applied to the measurement of clorazepate and its metabolites in blood and urine following a single 15-mg dose of clorazepate dipotassium.

Disposition of three benzodiazepines after single oral administration in man

Three benzodiazepines in equipotent doses: oxazepam 15 mg, dipotassium chlorazepate 10 mg and diazepam 5 mg, were administered in single, oral doses to seven healthy volunteers in a three-way cross-over study. The serum concentrations of oxazepam, N-desmethyldiazepam and diazepam were followed for 72 hours by gas chromatography and electron capture detection. The absorption of diazepam was most rapid and the mean time required to reach peak serum concentration was 45 minutes, followed by N-desmethyldiazepam 80 minutes and oxazepam 114 minutes. The serum concentration decay curves were biphasic with terminal mean half-lives of 48, 62 and 11 hours for diazepam, N-desmethyldiazepam and oxazepam, respectively. The mean and individual serum concentration time data were fitted to a two-compartment open model with first order absorption using a non linear least square program. The mean serum data fitted the model well. The same rank order was obtained with mean absorption half-lives as when comparing mean peak times while slightly shorter terminal half-lives were obtained in the curve fitting of mean serum data. Due to irregularities in the serum concentration time curves only five out of the 21 sets of individual data could satisfy the convergence criterion. The obtained parameters in the curve fitting were also accompanied with very large asymptotic standard deviations.

GLC determination of plasma drug levels after oral administration of clorazepate potassium salts

Plasma nordiazepam levels resulting from the oral administration of clorazepate potassium salts were determined by a sensitive GLC assay. Nordiazepam and the internal standard (diazepam) were selectively extracted into ether at pH 9.2, hydrolyzed to their respective benzophenones, and quantified by electron-capture detection. The assay was used in a comparative bioavailability study of single equimolar oral doses of monopotassium and dipotassium salts of clorazepate in dogs. Both clorazepate salts were rapidly absorbed and exhibited mean peak total drug levels after 1 hr. Clorazepate levels accounted for about 50% of the total drug levels present. No statistical difference in the plasma drug levels of clorazepate mono- and dipotassium salts and the metabolite was found in dogs.

Clinical and biochemical comparison of clorazepate and diazepam

Clorazepate and diazepam were compared with respect to clinical effectiveness and concentrations of benzodiazepine compounds in plasma in 15 severely anxious outpatients. Each patient was studied in a double blind trial incorporating two-week periods of the two drugs and of placebo. The doses were almost equimolar—5 mg diazepam or 7·5 mg clorazepate three times daily. Clinical progress was assessed by visual analogue scales and by the Symptom Rating Test. Psychopathology scores were highest at the end of the placebo periods, and lowest at the end of the clorazepate periods, regardless of the order of treatments. After diazepam, both diazepam and N-desmethyldiazepam (nordiazepam) were detected in blood, and after clorazepate, only N-desmethyldiazepam was detected. N-Desmethyldiazepam concentrations were higher after clorazepate. Clinical progress was apparently related to the concentration of N-desmethyldiazepam in plasma.