Blood drug concentrations of benzodiazepines correlate poorly with actual driving impairment.

BACKGROUND: The use of benzodiazepine receptor agonists can significantly impair driving performance. The aim of this review was to determine if there is a relation between blood concentrations of these drugs and the degree of driving impairment. METHODS: A literature search was conducted to identify driving studies that examined the effects of benzodiazepine receptor agonists. Studies were included if the on-the-road driving test was employed, using the standard deviation of lateral position (SDLP), i.e., the weaving of the car, as primary outcome measure. RESULTS: A total of 24 studies were identified that employed the on-the-road driving test to examine driving performance after administration of benzodiazepine receptor agonists. Eleven of these studies (45.8%) measured blood drug concentrations after the on-the-road driving test was performed. Technical reports of some of these studies provided individual data on blood drug concentrations and ΔSDLP (the ΔSDLP difference between drug and placebo). While group differences in concentrations were found as evidenced by significant effects of dose and time of driving since time of drug ingestion, no significant relationship between individual blood drug concentrations and ΔSDLP was found in any of the studies. CONCLUSION: While group mean average ΔSDLP and blood drug concentration sometimes correlate, individual differences in blood drug concentrations of benzodiazepine receptor agonists correlate poorly with driving impairment. From the currently available data, it must be concluded that there are no significant relationships between individual blood drug concentration and ΔSDLP. Future driving studies should assess blood drug levels as a standard procedure, to enable further research into the relationship between blood drug concentration and performance impairment.

Comparison by means of bispectral index score, between anxiolysis induced by diazepam and sedation induced by midazolam.

AIM: Bispectral Index Score (BIS) is an objective tool to assess sedation depth. Benzodiazepines have different pharmacological profiles and diazepam may be safer than midazolam in this setting. The aim of this study was to compare BIS values observed during anxiolysis after diazepam versus sedation after midazolam. METHODS: Thirty-six patients were randomly assigned to 3 groups: group 1 was treated with i.v. diazepam, groups 2 and 3 with iv midazolam 1 and 3 mg, respectively. Sedation was monitored clinically and by means of BIS. BIS values were evaluated as area under the curve (AUC) and compared by variance analysis. The statistical comparison of other data was performed by variance analysis or, alternatively, the χ2 according to Yates. The statistical significance was indicated by P values <0.05. RESULTS: AUC values were significantly lower after midazolam when compared to AUC values registered in diazepam treated patients; 22.6% of the group 3 patients showed BIS values <80, versus 0.4% of group 1 patients. CONCLUSION: Diazepam has a safer profile, with BIS values and clinical conditions according to the definition of minimal and/or moderate sedation. Diazepam represents the safer drug for anxiety management in dentistry, because regularly produces a state of sedation during which verbal contact with the patient is maintained and carry a margin of safety wide enough to render loss of consciousness unlikely.

Effects of organic solvents on the time-dependent inhibition of CYP3A4 by diazepam.

The effects of organic solvents, acetonitrile, dimethyl sulfoxide (DMSO), and methanol, which are used to dissolve lipophilic test compounds and cytochrome P450 (P450) substrates, and carried into pre-incubation at 1% (v/v), on time-dependent inhibition of CYP3A4 by diazepam, were evaluated using human liver microsomes (HLM) and recombinant human P450 expressed microsomes (rCYPs). The inactivation kinetics of CYP3A4 by diazepam dissolved in acetonitrile and methanol were almost equal with k(inact)/K(I) values, 0.095 and 0.15 min(-1) mM(-1) for HLM and 1.1 and 1.4 min(-1) mM(-1) for rCYP3A4, respectively. In contrast, the inactivation by diazepam dissolved in 1% DMSO significantly decreased and the kinetic parameter could not be calculated. The formation rate of nordiazepam and temazepam metabolized from diazepam dissolved in DMSO were approximately half of those using substrate dissolved in acetonitrile and methanol in both HLM and rCYP3A4. Dixon plots revealed that the metabolism of diazepam in rCYP3A4 were inhibited by DMSO in a competitive or mixed-type manner with K(i) (inhibition constant) values of 6 and 24 mM for nordiazepam and temazepam, respectively. In conclusion, the time-dependent inhibition of CYP3A4 by diazepam was attenuated by DMSO, while acetonitrile and methanol had no effect. The metabolite formation profile under the conditions tested suggested that DMSO competitively inhibit the formation of the reactive metabolites of diazepam by CYP3A4. The effect of organic solvents should be taken into consideration when evaluating the in vitro time-dependent inhibition of new chemical entities.

Toxicological data and growth characteristics of single post-feeding larvae and puparia of Calliphora vicina (Diptera: Calliphoridae) obtained from a controlled nordiazepam study.

Larvae of the Calliphora vicina (Diptera: Calliphoridae) were reared on artificial food spiked with different concentrations of nordiazepam. The dynamics of the accumulation and conversion of nordiazepam to its metabolite oxazepam in post-feeding larvae and empty puparia were studied. Analysis was performed using a previously developed liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. This method enabled the detection and quantitation of nordiazepam and oxazepam in single larvae and puparia. Both drugs could be detected in post-feeding larvae and empty puparia. In addition, the influence of nordiazepam on the development and growth of post-feeding larvae was studied. However, no major differences were observed for these parameters between the larvae fed on food containing nordiazepam and the control group. To our knowledge, this is the first report describing the presence of nordiazepam and its metabolite, oxazepam, in single Calliphora vicina larvae and puparia.

Effects of diazepam and its metabolites on nocturnal melatonin secretion in the rat pineal and Harderian glands. A comparative in vivo and in vitro study.

We investigated the effects of diazepam (DZP) and its three metabolites: nordiazepam (NZP), oxazepam (OZP), and temazepam (TZP) on pineal gland nocturnal melatonin secretion. We looked at the effects of benzodiazepines on pineal gland melatonin secretion both in vitro (using organ perifusion) and in vivo in male Wistar rats sacrificed in the middle of the dark phase. We also examined the effects of these benzodiazepines on in vivo melatonin secretion in the Harderian glands. Neither DZP (10(-5)-10(-6)M) nor its metabolites (10(-4)-10(-5)M) affected melatonin secretion by perifused rat pineal glands in vitro. In contrast, a 10(-4)M suprapharmacological concentration of DZP increased melatonin secretion of perifused pineal glands by 70%. In vivo, a single acute subcutaneous administration of DZP (3 mg/kg body weight) significantly affected pineal melatonin synthesis and plasma melatonin levels, while administration of the metabolites under the same conditions did not. DZP reduced pineal melatonin content (-40%), N-acetyltransferase activity (-70%), and plasma melatonin levels (-40%), but had no affects on pineal hydroxyindole-O-methyltransferase activity. Neither DZP nor its metabolites affected Harderian gland melatonin content. Our results indicate that the in vivo inhibitory effect of DZP on melatonin synthesis is not due to the metabolism of DZP. The results also show that the control of melatonin production in the Harderian glands differ from that observed in the pineal gland.

Binding of [3H]CB 34, a selective ligand for peripheral benzodiazepine receptors, to rat brain membranes.

The 2-phenyl-imidazo[1,2-a]pyridine derivative CB 34 is a ligand for peripheral benzodiazepine receptors. The binding of [3H]CB 34 to rat cerebrocortical membranes was characterized. Specific binding was rapid, reversible, saturable and of high affinity. Kinetic analysis yielded association and dissociation rate constants of 0.2x10(8) M(-1) min(-1) and 0.29 min(-1), respectively. Saturation binding experiments revealed a single class of binding sites with a total binding capacity of 188+/-8 fmol/mg protein and an apparent dissociation constant of 0.19+/-0.02 nM. Specific [3H]CB 34 binding was inhibited by ligands selective for peripheral benzodiazepine receptors, whereas, with the exception of flunitrazepam and diazepam, ligands for central benzodiazepine receptors were inactive. Of the brain regions examined, the density of the [3H]CB 34-binding sites was greatest in the hypothalamus and lowest in the cerebral cortex. [3H]CB 34 is thus a potent and selective ligand for peripheral benzodiazepine receptors and should be proven useful for studies of the roles of these receptors.

The effect of chronic benzodiazepines exposure on body weight in rats.

Changes in body weight (BW) in female rats treated for 5 weeks (wk) with weekly subcutaneous implantation of silastic capsules containing different benzodiazepines (BZs): diazepam (DZ) 90, 180, 360 and 540 mg wk-1; nordiazepam (ND) 600 mg wk-1; oxazepam (OX) 600 mg wk-1 and flunitrazepam (FN) 540 mg wk-1 and in male rats exposed to DZ (540 mg wk-1) were evaluated herein. Rats (female and male) implanted with empty capsules served as controls. The BW gain was significantly higher in male than in female rats (both DZ-treated and controls). The BW gain increased with increasing doses of DZ but slowed with time of exposure. In comparison to control rats, the BW gain was significantly higher in DZ-(540 mg wk-1) and OX- but not in ND- and FN-treated female rats. However, the differences between BZs were not of statistical significance. In rats exposed to empty capsules (male, female); DZ (male); ND and OX (female) the BW gain increased with time (1-4 wk) while in rats exposed to DZ and FN (female) the BW stabilised within 2 wk. Acute injection of the central BZ receptor antagonist, flumazenil (40 mg kg-1, i.v., 5th wk of chronic exposure), tended to inhibit the time-related BW gain in rats exposed to empty capsules (male, female), DZ (male), ND and OX (female) but did not affect the BW in DZ- (540 mg wk-1) and FN-exposed rats (female) where BW stabilised prior to FLU injection. Repeated administration of flumazenil (30 mg kg-1 wk-1, i.p.) did not affect the BW gain in DZ- and ND-treated female rats. The present data indicate that different BZs have different effects on BW gain in the rat suggesting that different subtypes of BZ receptors are involved.

Evidence against oppositional and pharmacokinetic mechanisms of tolerance to diazepam's sedative effects.

Acute administration of diazepam (2 mg/kg i.p.) to rats decreased the number of head-dips, locomotor activity and the number of rears made in the holeboard apparatus, indicating sedative effects. After daily treatment for 7 days with diazepam (2 mg/kg) tolerance developed to all these behavioural effects, despite serum concentrations of diazepam and N-desmethyldiazepam significantly higher than those following acute treatment. After 7 drug-free recovery days the rats were quite unresponsive to a probe dose of diazepam (2 mg/kg) and although there was a gradual recovery of responsiveness to diazepam, the reduction in rears still did not reach the level of the acute group even after 21 drug-free days. There was evidence for pharmacokinetic changes when probe doses of diazepam were given after 7, 14 or 21 recovery days. Lower levels of diazepam and higher levels of N-desmethyldiazepam than following an acute dose to the drug-naïve group were detected, indicating that the chronic treatment had resulted in a persistently enhanced rate of N-demethylation. It is argued that these changes do not fully account for the reduced responsiveness to the probe doses, and nor can they account for the gradual return of response over the 3-week recovery period. There were no detectable scrum concentrations of either compound 24 h after the end of the chronic treatment. However, no rebound increases in behavioural responses were detected at any time-point in withdrawal. Thus, the mechanism underlying this behavioural tolerance was not oppositional in nature. It is suggested that a situation-independent learned behavioural strategy is the most likely mechanism for the observed tolerance.

Flumazenil, diazepam, nordiazepam and oxazepam interactions on plasma protein binding.

The effect of flumazenil (FLU) on plasma protein binding of diazepam (DZ), nordiazepam (ND) and oxazepam (OX) was determined in plasma from drug-naive dogs to which graded concentrations of tested drugs alone and in combination were added. The results revealed that as the concentration of FLU added to plasma alone was increased its binding with plasma proteins decreased and that there were no significant binding interactions between FLU and OX, ND and DZ.

Mesolimbic dopamine turnover effects of benzodiazepines do not correlate with sedative and muscle-relaxant potencies.

Benzodiazepines are known to decrease the dopamine turnover in the mesolimbic dopaminergic system in stimulated rather than in basal conditions. Stimulation of dopamine turnover can be achieved by administration of the dopamine antagonist haloperidol. In the present paper, we tested the hypothesis that the effect of the benzodiazepines on the mesolimbic dopamine turnover is mediated by the benzodiazepine receptor, comparing the minimal potency of inhibition of the stimulated dopamine turnover with the ED50 values for the sedative and muscle-relaxant actions of the compounds. Five compounds were studied: desmethyldiazepam, lorazepam, flunitrazepam, triazolam and brotizolam. In contrast to the other compounds, lorazepam appeared to have no effect on the haloperidol-induced increase in DOPAC concentration. The relative potency of the benzodiazepines for this effect on the haloperidol-induced DOPAC increase is very different from that on sedation and muscle relaxation, suggesting that the effect on the mesolimbic dopamine turnover is not mediated by the classical benzodiazepine receptor. Since the background of this study was the relation between the dopaminergic effects and the development of psychotic symptoms during benzodiazepine withdrawal, this different pattern of the benzodiazepines is suggested to be an indication that benzodiazepines may differ qualitatively in the development of withdrawal symptoms after long-term treatment.

Pharmacokinetics of nordiazepam in physical dependence and precipitated abstinence in dogs.

Previous studies suggested that the extensive accumulation of benzodiazepines is an important factor in the induction of physical dependence. The mechanistic basis for accumulation of nordiazepam (ND) and its metabolite, oxazepam (OX), have been examined in crossover studies in drug-naive and in ND-dependent dogs that exhibited a flumazenil-precipitated abstinence syndrome. ND and parent OX have similar pharmacokinetic profiles. Steady-state plasma levels of ND and OX cannot be predicted from single-dose pharmacokinetics. Reduced plasma clearance of ND and altered plasma protein binding were observed in dogs physically dependent upon ND. The benzodiazepine antagonist, flumazenil, significantly reduces steady-state plasma levels of total and free ND.

Differences in the duration of sedative and anxiolytic effects of desmethyldiazepam in two outbred Wistar strains.

Different sensitivities to benzodiazepines have been described for various strains of both rats and mice suggesting that variations in biological features of the animals are responsible for these differences. Since all reports concern inbred strains, we studied two outbred Wistar strains which are used routinely in several research disciplines. The pharmacodynamics of desmethyldiazepam (DMD), the main active metabolite of diazepam in man, were compared for male rats of the Riv:TOX strain (from the National Institute of Public Health and Environmental Protection) and the Crl:(WI)BR strain. The duration of sedative action of DMD after oral administration, as derived from suppression of the nocturnal locomotor activity, was longer in the Riv:TOX strain than in the Crl:(WI)BR strain. Accordingly, suppression of novelty-induced corticosterone release as an index of anxiolytic action was observed 11 hours after DMD administration in Riv:TOX rats but not in Crl:(WI)BR rats. At that time, serum DMD concentration was shown to be higher in the Riv:TOX strain than in the Crl:(WI)BR strain. The data are discussed in relation with possible metabolic differences between the two strains.

Effect of chronic oral delorazepam on in vitro and in vivo hepatic drug-metabolizing enzyme activities in the rat.

In vivo (delorazepam clearance) and in vitro (monooxygenase activity markers) alterations in drug metabolism and the extent of enzyme induction of the hepatic cytochrome P-450 system were evaluated after oral administration of delorazepam (2.5, 25 and 150 mg/kg) for two weeks to male Sprague-Dawley rats. This benzodiazepine had no significant effect on drug metabolizing enzymes, except for slight enhancement of in vitro aniline p-hydroxylase activity which occurred at doses approximately 100 times those used clinically (0.5-2 mg). Under the likely conditions of exposure to delorazepam in human therapy therefore, such alteration in liver enzymes would be unlikely to have clinical relevance.

Effect of the benzodiazepines diazepam, des-N-methyldiazepam and midazolam on corticosteroid biosynthesis in bovine adrenocortical cells in vitro; location of site of action.

Diazepam and midazolam inhibited cortisol and aldosterone synthesis in bovine adrenal cells in vitro. The biologically active metabolite des-N-methyldiazepam did not. Midazolam was a more potent inhibitor (IC50: 6 micrograms/ml) than diazepam (IC50: 13 micrograms/ml) in ACTH-stimulated cells. Both compounds inhibited steroidogenesis at several points in the biosynthetic chain; the greatest effects were on 17 alpha hydroxylation and 21 hydroxylation. Diazepam had a relatively greater effect on 17 alpha hydroxylation; midazolam on 21 hydroxylation. Both were less potent inhibitors of 11 beta hydroxylation and had little apparent effect on side chain cleavage. Thus microsomal hydroxylation is more vulnerable to benzodiazepines than mitochondrial hydroxylation. It is suggested that the drugs act by competing with steroid mixed function oxidases for cytochrome P-450. The plasma concentrations required for these effects are high in relation to therapeutic levels but may be achieved, for example, during acute infusions or when they are used in combination with imidazole drugs such as cimetidine.

[Chlordesmethyldiazepam and prolactinemia during surgical stress]. / Clordemetildiazepam e prolattinemia in corso di stress chirurgico.

The per-operative plasma prolactin levels in 16 male patients undergoing plastic-reconstructive surgery were studied. 8 patients received chlordesmethyldiazepam 0.1 mg/kg-1 i.v. (group C), 8 sodium thiopental 5 mg/kg-1 i.v. (Group T) in anaesthesia induction. All patients were premedicated by diazepam 0.15 mg/kg-1 by mouth 90 min. before anaesthesia induction and atropine 0.007 mg/kg-1 i.v. just before induction, and received succinylcholine 1 mg/kg-1 i.v. and an endotracheal tube for mechanically controlled ventilation. Anaesthesia maintenance was assured by isoflurane 0.5-2.5% in a N2/O2 (2/1) gas mixture. Blood samples were collected from each patient at the following times; 24 h before surgery (t0); 30 min after skin incision (t1); 30 min after extubation (t2). Significant variation of blood prolactin levels are not been shown.

Kinetics of drug action in disease states. XXV. Effect of experimental hypovolemia on the pharmacodynamics and pharmacokinetics of desmethyldiazepam.

It has been reported that hypovolemia secondary to extensive blood loss alters the functionality of the central nervous system and is associated with changes in the dose requirements or intensity of action of various central nervous system depressants, including a benzodiazepine. To investigate the mechanism(s) of this effect, the influence of experimental hypovolemia on the pharmacodynamics, receptor binding and pharmacokinetics of a benzodiazepine drug was determined. Adult male Sprague-Dawley rats were made hypovolemic by removal of about 30% of their blood over 30 min. An i.v. infusion of desmethyldiazepam (DDZP) was started 30 min later and continued until the animals lost their righting reflex. Compared to results obtained with normal controls, the hypovolemic rats required about one-half the dose of DDZP to produce loss of righting reflex and had significantly lower DDZP concentrations in serum and cerebrospinal fluid at that time. This effect of substantial blood removal could not be reversed by prompt return of the removed blood to the animals. Experimental hypovolemia had no apparent effect on the in vitro binding of tritiated diazepam to benzodiazepine receptor sites in the cerebral cortex of rats. The plasma clearance of DDZP was decreased significantly and the biological half-life was increased in hypovolemic rats compared to normal animals when both received a 30-mg/kg dose by i.v. infusion over 10 min. It is concluded that acute hemorrhagic hypovolemia increases the sensitivity of the central nervous system to the depressant effect of DDZP and decreases the body clearance of that drug in rats. Thus, the pharmacodynamics as well as the pharmacokinetics of a benzodiazepine are altered by hypovolemia.

Kinetics of drug action in disease states. XXIV. Pharmacodynamics of diazepam and its active metabolites in rats.

The purpose of this investigation was to determine the relative contribution of diazepam and its active metabolites (desmethyldiazepam, oxazepam and temazepam) to the hypnotic activity of this benzodiazepine drug and to assess the role of rate of drug administration as a determinant of the relative concentrations of diazepam and its active metabolites in serum and in the central nervous system at the onset of a predefined pharmacologic endpoint. Rats were given i.v. infusions of diazepam to onset of loss of righting reflex. Samples of cerebrospinal fluid (CSF), blood (for serum) and brain were obtained at that time and were analyzed for diazepam and its active metabolites. Based on the results of six experiments on groups of 6 to 14 rats performed at the same time of day over 11 months, the pharmacologic response of the animals was found to be relatively consistent, with little variation between rats and between experiments in body weight-normalized effective dose and in diazepam serum and CSF concentrations. All three active metabolites of diazepam were found in serum, CSF and brain; they were relatively more prominent in CSF than in serum. Variation of the diazepam infusion rate (four rates between 0.10 and 0.34 mg/min per approximately 200-g rat) was associated with changes in average onset time (50 to 10 min) and dose (26 to 17 mg/kg) required to produce the pharmacologic effect. The drug and metabolite concentrations in CSF determined in these experiments, together with corresponding concentrations obtained by infusion of each active metabolite individually, yielded estimates of their relative hypnotic potency that were unaffected by differences in serum protein binding and tissue distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of chlordemethyldiazepam on blood cortisol during surgical stress]. / Effetti del clordemetildiazepam sulla cortisolemia in corso di stress chirurgico.

The pre-operative plasma cortisol levels in 16 male patients undergoing plastic-reconstructive surgery were studied. 8 patients received chlordesmethyldiazepam 0.1 mg/kg-1 i.v. (group C), 8 sodium thiopental 5 mg/kg-1 i.v. (group T) in anaesthesia induction. All patients were premedicated by diazepam 0.15 mg/kg-1 by mouth 90 min before anaesthesia induction and atropine 0.007 mg/kg-1 i.v. just before induction, and received succinylcholine 1 mg/kg-1 i.v. and an endotracheal tube for mechanically controlled ventilation. Anaesthesia maintenance was assured by isoflurane 0.5-2.5% in a N2O/O2 (2/1) gas mixture. Blood samples were collected from each patient at the following times: 24 h before surgery (t0); 30 min after skin incision (t1); 30 min after extubation (t2). Significant variations of blood cortisol levels have not been shown.

Imipramine treatment alters the pharmacokinetics and pharmacodynamics of diazepam.

This report describes observations of the relationship between the pharmacokinetics and pharmacodynamics of diazepam (7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one ; 5 mg/kg) during the concomitant administration of diazepam and imipramine hydrochloride (5-[3-(dimethylamino)propyl]-10,11-dihydro-5H-dibenz[b,f]azepine monohydrochloride; 20 and 50 mg/kg) to rats. We measured plasma, brain, and liver concentrations of diazepam and its metabolites in rats by high-performance liquid chromatography. The concomitant use of imipramine hydrochloride increased diazepam and desmethyldiazepam concentrations, but decreased temazepam and oxazepam concentrations in rat plasma. Diazepam plasma protein binding was unaltered. The liver concentrations of diazepam and its metabolites showed similar changes in their plasma concentrations. The concomitant use of imipramine hydrochloride increased the concentrations of diazepam and its metabolites in the brain. We also studied the effect of benzodiazepines on convulsions induced by pentylenetetrazole (6,7,8,9-tetrahydro-5H-tetrazolo[1,5-a] azepine; 135 mg/kg) in rats. The concomitant use of imipramine hydrochloride led to an increased antipentylenetetrazole effect of diazepam. This result is in accordance with the findings on brain concentrations of diazepam and its metabolites.

Effects of propranolol, atenolol, and chlordesmethyldiazepam on response to mental stress in patients with recent myocardial infarction.

Stress testing was carried out by two stressors, mental arithmetic and Sacks-Levy's test in randomized sequence, in 64 male patients with a mean age of 51 +/- 7 years in NYHA Classes I or II within 3 months after acute myocardial infarction. The stress profile was obtained after drug withdrawal by continuous recording of electrocardiogram, frontal electromyogram, and peripheral skin temperature and conductance. Blood pressure was measured each minute by cuff. The patients were subdivided into 4 groups of 16 each and were studied in an identical fashion after a 48-h oral treatment with propranolol 120 mg daily, atenolol 100 mg daily, chlordesmethyldiazepam 2 mg daily, or placebo. During stress, signs of myocardial ischemia or pump failure were not observed; minor arrhythmias were recorded. Cardiovascular activation was observed with significant increments (p less than 0.001) in heart rate, systolic and diastolic blood pressures in all 4 groups for both stressors with a slightly greater effect of mental arithmetic; Sacks' test was more effective on the frontal electromyograph response. Following beta blockade the stress profile of heart rate was significantly lower and flattened. The stress profile of blood pressure was also lower, but the reduction in the increment during stress was not significant. No differences were observed in the effects of the two beta blockers; no significant changes were evident in the stress profile of the noncardiovascular psychophysiologic indexes. Stress profiles were not altered by the benzodiazepine. In conclusion beta-blocker agents seem to be more useful than anxiolytic drugs in preventing cardiovascular activation induced by mental stress in patients with recent myocardial infarction.