Rapid determination of diazepam and nordiazepam in plasma by electron capture gas—liquid chromatography

The effect of flumazenil (Ro 15-1788) in the management of self-induced benzodiazepine poisoning. A double-blind controlled study

A double-blind randomized study was performed to evaluate the efficacy and safety of flumazenil, a benzodiazepine antagonist. The study comprised 52 patients admitted to an intensive care unit because of suspected pure or mixed benzodiazepine poisoning. The degree of consciousness was assessed according to a modified Glasgow Coma Scale (MGCS), graded from 4 to 20, immediately before and at consecutive intervals after an i.v. injection of flumazenil or placebo. If there were no clear signs of arousal within 5 min after the blind injection, an injection of flumazenil was given in open design. Five minutes after the blind administration of active drug the MGCS score was increased by an average of 7.4 (p less than 0.001) in the flumazenil group. In the placebo group the average MGCS score of 7.8 on admission was not significantly increased by placebo, but 5 min after flumazenil injection it had increased by 7.3 to 15.1 (p less than 0.001). Patients who had ingested both alcohol and benzodiazepines were aroused as promptly and clearly (MGCS +8.8; p less than 0.001) as those who had taken benzodiazepines alone (MGCS +8.4; p less than 0.001). The patients poisoned with a combination of benzodiazepines and other hypnotic drugs responded less, but still highly significantly (MGCS +5.8; p less than 0.001). Flumazenil was well tolerated and the safety of the antidote seems acceptable. It is concluded that flumazenil can facilitate differential diagnosis and that it is an effective tool in the treatment of drug overdosage when benzodiazepines are involved.

Chromatographic method for the determination of diazepam, pyridostigmine bromide, and their metabolites in rat plasma and urine

This study describes a chromatographic method for the determination of diazepam, an anxiolytic drug that is also used as an antidote against nerve agent seizures, its metabolites N-desmethyldiazepam, and temazepam, the anti-nerve agent drug pyridostigmine bromide (PB; 3-dimethylaminocarbonyloxy-N-methyl pyridinium bromide) and its metabolite N-methyl-3-hydroxypyridinium bromide in rat plasma and urine. The compounds were extracted using C18 Sep-Pak Vac 3cc (500 mg) cartridges and separated using isocratic mobile phase of methanol, acetonitrile and water (pH 3.2) (10:40:50) at a flow-rate of 0.5 ml/min in a period of 12 min, and UV detection ranging between 240 and 280 nm. The limits of detection for all analytes ranged between 20 and 50 ng/ml, while limits of quantitation were 100 ng/ml. Average percentage extraction recoveries of five spiked plasma samples were 79.1+/-7.7, 83.5+/-6.4, 83.9+/-5.9, 71.3+/-6.0 and 77.7+/-5.6, and from urine 79.4+/-7.9, 83.1+/-6.9, 73.6+/-7.7, 74.3+/-7.1 and 77.6+/-5.9 for diazepam, N-desmethyldiazepam, temazepam, pyridostigmine bromide, and N-methyl-3-hydroxypyridinium bromide, respectively. The relationship between peak areas and concentration was linear over the range between 100 and 1000 ng/ml. This method was applied to determine the above analytes following a single oral administration in rats as a tool to study the pharmacokinetic profile of each compound, alone and in combination.

Rapid and simple chromatographic method for the determination of diazepam and its major metabolites in human plasma and urine

A simple, rapid, sensitive and selective HPLC method has been developed for the analysis of diazepam (DZP) and its major metabolites, N-desmethyldiazepam (DMDZP), temazepam (TZP) and oxazepam (OZP), in plasma and urine, using clonazepam (CZP) as the internal standard and chloroform as the extracting solvent, with a 10 ng/ml limit of quantitation for the four assayed drugs, and an average (+/-S.D.) recovery of 87.7+/-6.46%, 92.9+/-5.31%, 91.4+/-4.01% and 91.7+/-2.68% for DZP, DMDZP, TZP and OZP, respectively (from plasma), and 89.6+/-2.26%, 90+/-4.24%, 87.45+/-0.64% and 94.50+/-0.71% for DZP, DMDZP, TZP and OZP, respectively (from urine). The method has also proved to be selective and reproducible.

A placebo-controlled trial of flumazenil given by continuous infusion in severe benzodiazepine overdosage

A controlled trial was performed to study the effect and any adverse reactions of continuously infused flumazenil in severe benzodiazepine overdosage. The study comprised 51 adults admitted to an intensive care unit with poisoning. Enrollment criteria were unconsciousness on admission and a clear response within 5 min after an i.v. bolus injection of 1 mg flumazenil. The level of consciousness was assessed according to a modified Glasgow coma scale immediately before and at defined intervals up to 12 h after injection. A double-blind infusion was started 15 min after the bolus injection and administered for 5 h. The patients were randomly allocated to one of three groups: a group given flumazenil 0.5 mg/h, a group given flumazenil 0.1 mg/h and a placebo group. The groups were comparable in age, sex and toxicological laboratory results. There were no significant differences between the groups in the average coma score on admission or 15 min after the bolus injection. In the flumazenil 0.5 mg/h group the level of consciousness remained unchanged between the 15-min recording and the subsequent assessments. In the two other groups the level of consciousness decreased significantly during the course of the infusion. The infusions were well tolerated. It is concluded that a continuous infusion of 0.5 mg of flumazenil per hour can prevent relapse into coma in patients with severe benzodiazepine poisoning aroused with a single injection of the antagonist.

Hexapropymate self-poisoning causes severe and long-lasting clinical symptoms

Cases of hexapropymate poisoning requiring intensive care in an urban region of Sweden (420,000 inhabitants) were collected over 2.5 years (1985 to 1987). Only patients with serum hexapropymate concentrations above 5.5 mg/L (30 mumol/L) and with a negative history for intake of tricyclic antidepressants, phenothiazines, barbiturates, antihistaminic drugs and opiates were included. Clinical data about 8 intoxication events in 6 patients were evaluated retrospectively. Initial symptoms included coma, hypotension, hypothermia, and hypoventilation. Maximum coma depth (Glasgow coma score) was 3 to 5 in 5 out of 8 events. On 7 occasions assisted ventilation was required (for 12 hours or more in 5 events). There was no relationship between serum concentrations of hexapropymate and severity of clinical symptoms. All patients survived. Detailed analysis of the drug elimination in one patient showed a terminal elimination half-life of 21 hours, which is longer than previously reported (5 hours). The indications for use of this hypnotic drug may vary between doctors since an 8-fold variation was seen in drug prescription between Swedish counties in 1987. Poisoning with hexapropymate is a serious condition which may require symptomatic treatment in the intensive care unit. The clinical picture is similar to that seen in patients with burbiturate intoxication. There is no role for active forced elimination of the drug. It is questionable whether the clinical value of the drug is outweighted by its toxicity.

Applications to analytic chemistry: an evaluation of stable isotopes in mass spectral drug assays

We evaluated stable isotope analogues (SIAs) as internal standards in mass spectral drug assays on the analytic parameters of accuracy, precision, specificity, and limit of quantitation. Only one literature report suggests that the use of an SIA made an assay more accurate, although theoretic considerations strongly support their use. There is substantial evidence, however, that their use made assays more precise. Potentially, the chromatographic peak shape and retention time of the SIA can be compared with those of the analyte to support assay specificity, and this type of comparison has been implemented as a new computer program (QSIMPS). There is some evidence that SIAs can serve in "carrier" substances to increase recoveries and thus lower the limit of quantitation of an assay. However, the use of large amounts of an SIA (relative to the analyte) leads to analytic imprecision, because of memory effects, large blank values, and unacceptable confidence limits.

Pharmacokinetics of diazepam from a controlled release capsule in healthy elderly volunteers

A single dose open labelled two-way randomized crossover study was used to assess the pharmacokinetics of diazepam from a controlled release capsule relative to standard release tablets in elderly volunteers. Eighteen volunteers received a single 15 mg controlled release capsule or a 5 mg tablet t.i.d. on one day. Diazepam plasma concentrations were determined at specific times over a 96-h interval by an electron capture-gas chromatographic method. Mean plateau plasma concentrations endured from 2 to 24 h avoiding the peak to trough fluctuations associated with conventional t.i.d. dosing. Similar areas under the plasma concentration-time curve (AUC) values indicated equal extent of absorption between formulations and regimens. Comparing parameters in this same elderly population to a young adult population, previously administered the controlled release capsule, shows lower maximum concentrations and a longer plateau duration in the elderly volunteers. Although there is a twofold increase in the mean diazepam half-life in the elderly when compared to young adults, the estimated apparent volume of distribution increased proportionately with half-life to maintain a constant clearance. Thus, the total body clearance of diazepam appears to be age independent. The age-dependent pharmacokinetics observed in this study are consistent with previously reported data involving diazepam. Overall, the controlled release capsule administered once daily mimics a t.i.d. regimen in elderly volunteers.

Pharmacokinetics of diazepam and nordiazepam in the cat

The cat has been used extensively as an experimental model for studying the pharmacology of compounds that exhibit CNS activity including diazepam and nordiazepam. However, since little is known about the distribution and elimination of diazepam in this species, the pharmacokinetics of diazepam and nordiazepam were studied in the cat following intravenous doses of 5, 10, and 20 mg/kg of diazepam and 5 and 10 mg/kg of nordiazepam. The disappearance of diazepam and nordiazepam from blood was fitted with classical equations. Theoretical and trapezoidal areas under the curve (AUCth and AUCtr) were calculated. The volumes of distribution (Vd beta) were calculated as model-independent parameters for diazepam and nordiazepam. Intrinsic hepatic clearance, extraction ratio, and tissue binding parameters were also calculated for diazepam. From the observed data, it is apparent that the blood concentrations and the resulting areas under the curves are proportional to the dose of diazepam administered and that the pharmacokinetics of diazepam were linear over the dose range studied. In addition, nordiazepam formed after diazepam administration appeared to be proportional to the dose of diazepam administered. The terminal elimination rate constant of nordiazepam remained constant over the dose range studied. It appears that both diazepam and nordiazepam are highly bound to tissue. The total body clearance of diazepam (4.72 +/- 2.45 mL/min/kg) is approximately six times that of nordiazepam (0.85 +/- 0.25 mL/min/kg). Approximately 50% of an administered dose of diazepam was biotransformed to nordiazepam in the cat.

Determination of peptidoaminobenzophenone (2-o-chlorobenzoyl-4-chloro-N-methyl-N'-glycylglycinanilide) and its metabolites in human plasma by glass capillary gas chromatography negative ion chemical ionization mass spectrometry--1

A highly sensitive and selective glass capillary gas chromatographic negative ion chemical ionization mass spectrometric assay was developed to measure peptidoaminobenzophenone(2-o-chlorobenzoyl-4-chloro-N-methyl-N'-glycylglycinanilide) and its metabolites; chlorodiazepam, chlorodesmethyldiazepam and lorazepam in human plasma. As peptidoaminobenzophenone underwent pyrolysis during gas chromatography, it was converted to a thermally stable aminoquinolone. Internal standards for these compounds were the respective deuterium labelled compounds. Calibration curves were prepared for the range of 1-100 ng ml-1. Interference by endogenous substances was negligible in the isobutane negative ion chemical ionization mode in contrast to the electron impact or positive ion chemical ionization mode. This method was used to determine the plasma levels in humans following oral administration of two 5 mg doses.

Influence of alcohol on the pharmacokinetics of diazepam controlled-release formulation in healthy volunteers

Twelve normal volunteers were empanelled in an open-label, three-way crossover study to evaluate the influence of alcohol on the pharmacokinetics of controlled-release diazepam capsules. Each volunteer received one 15-mg diazepam controlled-release capsule alone, concomitantly with alcohol or followed by alcohol 2 hours later. The mean plasma concentration-time profiles following both alcohol treatments were superimposable on the profile from the control. The mean plateau concentrations were observed to endure from 2 through 12 hours in all cases. The mean +/- S.D. areas under the plasma concentration-time curves from time zero to infinity were similar indicating no difference in the extent of absorption of diazepam in the presence of alcohol. The harmonic mean elimination half-lives were also similar. Overall, the pharmacokinetics and the release properties of controlled-release diazepam capsule were not influenced by alcohol in normal volunteers.

Clinical bioavailability evaluation of a controlled release formulation of diazepam

A controlled release formulation of diazepam was compared to equal daily dose of the trade tablet under single day and steady-state conditions. Virtually no differences were found in the mean steady-state concentrations of diazepam or its metabolites, N-desmethyldiazepam, when the subjects received the 5 mg trade table three times daily or the 15 mg controlled release formulation once daily. Similarly, there was no difference in mean diazepam or N-desmethyldiazepam plasma concentrations when single doses of the controlled release formulation were give to fed or fasted volunteers. These data indicate that the controlled release formulation produces plasma concentrations of diazepam and N-desmethyldiazepam comparable to those achieved with the same daily dose of the trade product given three times daily, suggesting that these regimens can be used interchangeably.

Determination of diazepam and its major metabolites in man and in the cat by high-performance liquid chromatography

A rapid, sensitive and specific high-performance liquid chromatography (HPLC) assay was developed for the determination of diazepam, and its major metabolites, oxazepam, temazepam and nordiazepam in plasma, blood, and urine of humans and cats. The assay for the compounds involves extraction into benzene--methylene chloride (90:10) from plasma, blood or urine buffered to pH 9.0. In both species the overall recovery of diazepam and its major metabolites from plasma or blood ranged from 60 +/- 3.2 to 89 +/- 13% (S.D.) and for urine from 79 +/- 7.9 to 93 +/- 10.5% (S.D.). The sensitivity limit of the assay using UV detection at 254 nm was 50 ng/ml of plasma and blood in both species except for human urine (post-Glusulase) which was 200 ng/ml. The HPLC assay was used to monitor the plasma concentration--time profile in humans following a 10-mg oral dose of diazepam and the blood concentration time profile of diazepam and nordiazepam in cats following a 10 mg/kg intravenous dose of either diazepam or nordiazepam. The HPLC assay data correlated well with data generated by an electron-capture--gas--liquid chromatography assay.

High-performance liquid chromatographic and gas-liquid chromatographic determination of diazepam and nordiazepam in plasma

A one-step method for extraction of diazepam, nordiazepam, and internal standard into toluene is followed by chromatographic separation and detection with either dual-wave-length high-performance liquid chromatography or electron-capture gas-liquid chromatography. Agreement between the two methods was excellent for diazepam (r = 0.99, n = 38) and good for nordiazepam (r = 0.96, n = 79) over a concentration range that included subtherapeutic, therapeutic, and toxic plasma levels.