Immediate and residual effects in man of the metabolites of diazepam

Physiologically-Based Pharmacokinetic and Pharmacodynamic Modeling of Diazepam: Unbound Interstitial Brain Concentrations Correspond to Clinical Endpoints

Benzodiazepines induce a series of clinical effects by modulating subtypes of GABA_A receptors in the central nervous system. The brain concentration-time profiles of diazepam that correspond to these effects are unknown, but can be estimated with physiologically-based pharmacokinetic (PBPK) modeling. In this study, a PBPK model for the 1,4-benzodiazepines diazepam and nordiazepam was developed from plasma concentration time-courses with PK-Sim^® software to predict brain concentrations. The PBPK model simulations accurately parallel plasma concentrations from both an internal model training data set and an external data set for both intravenous and peroral diazepam administrations. It was determined that the unbound interstitial brain concentration-time profiles correlated with diazepam pharmacodynamic endpoints. With a 30 mg intravenous diazepam dose, the peak unbound interstitial brain concentration from this model is 160 nM at 2 minutes and 28.9 nM at 120 minutes. Peak potentiation of recombinant GABA_A receptors composed of α1β2γ2s, α2β2γ2s, and α5β2γ2s subunit combinations that are involved in diazepam clinical endpoints is 108%, 139% and 186%, respectively, with this intravenous dose. With 10 mg peroral administrations of diazepam delivered every 24 hours, steady-state peak and trough unbound interstitial brain diazepam concentrations are 22.3 ± 7.5 nM and 9.3 ± 3.5 nM. Nordiazepam unbound interstitial brain concentration is 36.1 nM at equilibrium with this diazepam dosing schedule. Pharmacodynamic models coupled to the diazepam unbound interstitial brain concentrations from the PBPK analysis account for electroencephalographic drug effect, change in 13-30 Hz electroencephalographic activity, amnesia incidence, and sedation score time-courses from human subjects. This article is protected by copyright. All rights reserved.

Formation of biologically active benzodiazepine metabolites in Arabidopsis thaliana cell cultures and vegetable plants under hydroponic conditions

The use of recycled water for agricultural irrigation comes with the concern of exposure to crops by contaminants of emerging concerns (CECs). The concentration of CECs in plant tissues will depend on uptake, translocation and metabolism in plants. However, relatively little is known about plant metabolism of CECs, particularly under chronic exposure conditions. In this study, metabolism of the pharmaceutical diazepam was investigated in Arabidopsis thaliana cells and cucumber (Cucumis sativus) and radish (Raphanus sativus) seedlings grown in hydroponic solution following acute (7 d)/high concentration (1 mg L^-1), and chronic (28 d)/low concentration (1 μg L^-1) exposures. Liquid chromatography paired with mass spectrometry, ¹⁴C tracing, and enzyme extractions, were used to characterize the metabolic phases. The three major metabolites of diazepam - nordiazepam, temazepam and oxazepam - were detected as Phase I metabolites, with the longevity corresponding to that of human metabolism. Nordiazepam was the most prevalent metabolite at the end of the 5 d incubation in A. thaliana cells and 7 d, 28 d seedling cultivations. At the end of 7 d cultivation, non-extractable residues (Phase III) in radish and cucumber seedlings accounted for 14% and 33% of the added ¹⁴C-diazepam, respectively. By the end of 28 d incubation, the non-extractable radioactivity fraction further increased to 47% and 61%, indicating Phase III metabolism as an important destination for diazepam. Significant changes to glycosyltransferase activity were detected in both cucumber and radish seedlings exposed to diazepam. Findings of this study highlight the need to consider the formation of bioactive transformation intermediates and different phases of metabolism to achieve a comprehensive understanding of risks of CECs in agroecosystems.

Conversion factors for assessment of driving impairment after exposure to multiple benzodiazepines/z-hypnotics or opioids

AIMS

Norway has introduced legal concentration limits in blood for 28 non-alcohol drugs in driving under the influence cases. As of 2016 this legislation also regulates the assessment of combined effects of multiple benzodiazepines and opioids. We herein describe the employed methodology for the equivalence tables for concentrations of benzodiazepines/z-hypnotics and opioids implemented in the Norwegian Road Traffic Act.

METHODS

Legislative limits corresponding to impairment at blood alcohol concentrations (BAC) of 0.02%, 0.05% and 0.12% were established for 15 different benzodiazepines and opioids. This was based on a concept of a linear relationship between blood drug concentration and impairment in drug naïve users. Concentration ratios between these drugs were used to establish conversion factors and calculate net impairment using diazepam and morphine equivalents.

RESULTS

Conversion factors were established for 14 benzodiazepines/z-hypnotics (alprazolam, bromazepam, clobazam, clonazepam, etizolam, flunitrazepam, lorazepam, nitrazepam, nordiazepam, oxazepam, phenazepam, temazepam, zolpidem and zopiclone) and two opioids (methadone and oxycodone).

CONCLUSIONS

Conversion factors to calculate diazepam and morphine equivalents for benzodiazepines/z-hypnotics and selected opioids, respectively, have been operative in the Norwegian Road Traffic Act as of February 2016. Calculated equivalents can be applied by the courts to meter out sanctions.

Effect of a single dose of diazepam on balance measures in older people

OBJECTIVE

This study examines the effect of a single dose of diazepam on a spectrum of balance measures in healthy older subjects. The measures include static (postural sway), dynamic (anterior tibialis muscle activation latency), and a complex self-initiated task of balance (functional reach) in addition to neuropsychological tests of attention.

DESIGN

A double-blind, two-period, cross-over trial.

SETTING

The community surrounding a university hospital.

PARTICIPANTS

Community-dwelling, nonsmoking volunteers 65 years of age and older.

MEASUREMENTS

Measures included response to unexpected perturbation (platform/EMG muscle latency), self-initiated perturbation (functional reach), and a static measure of balance (postural sway). Neurocognitive tests (digital symbol substitution test, card sorting) were included to document the cognitive effect.

RESULTS

Twelve nonsmoking healthy subjects (average age = 70.4 years (66-76 years)) participated. The anterior tibalis muscle latency increased in response to a sudden perturbation with diazepam compared with placebo (TA latency 149 ms vs 142 ms, P < .001). Neurocognitive tests were adversely affected for 90 minutes after diazepam administration compared with placebo (P < .05). Other measures did not demonstrate significant effect of diazepam.

CONCLUSIONS

This is among the first reports showing that benzodiazepines affect neuromuscular processing related to balance control. Increased muscle latency to sudden perturbations may represent an effect of diazepam upon the oligosynaptic spinal reflex distinct from the sedation. Surface electromyography may be a valuable noninvasive tool for future studies of drug effect on balance and falls risk among older people.

Performance tests

This paper discusses the use of psychological performance tests to assess the effects of environmental stressors. The large number and the variety of performance tests are illustrated, and the differences between performance tests and other psychological tests are described in terms of their design, construction, use, and purpose. The stressor emphasis is on the effects of drugs since that is where most performance tests have found their main application, although other stressors, e.g., fatigue, toxic chemicals, are mentioned where appropriate. Diazepam is used as an example. There is no particular performance emphasis since the tests are intended to have wide applicability. However, vehicle-driving performance is discussed because it has been the subject of a great deal of research and is probably one of the most important areas of application. Performance tests are discussed in terms of the four main underlying models--factor analysis, general information processing, multiple resource and strategy models, and processing-stage models--and in terms of their psychometric properties--sensitivity, reliability, and content, criterion, construct, and face validity. Some test taxonomies are presented. Standardization is also discussed with reference to the reaction time, mathematical processing, memory search, spatial processing, unstable tracking, verbal processing, and dual task tests used in the AGARD STRES battery. Some comments on measurement strengths and appropriate study designs and methods are included.

Special problems relating to the use of hypnotics in the elderly

The problems experienced by elderly patients taking hypnotic drugs are reviewed. They include those associated with accumulation, tolerance, drug dependence and the intensity and duration of response. Biological mechanisms associated with ageing enhance some of these effects in the elderly. Care should be taken to define the precise indications for hypnotic use and to choose the correct drug and dose for the patient's condition and age.

The behavioral actions of diazepam and oxazepam are similar

In a double-blind and randomized study, we assessed the comparative pharmacodynamic profiles and behavioral effects of diazepam and oxazepam administered to young healthy volunteers. Diazepam 0.3 mg/kg or oxazepam 1.2 mg/kg or placebo were each administered orally to 13 subjects who were tested with tasks which measured learning and memory, cognition, psychomotor performance and mood before and for 9 h after treatment. The two drugs had similar actions, although subjective effects were milder after oxazepam, which also had a slower onset of action. There was no evidence of rebound behavioral impairment.

Single dose pharmacokinetics and pharmacodynamics of oral loprazolam in the elderly

The pharmacokinetics of the benzodiazepine hypnotic, loprazolam (1.0 mg orally), and the pharmacodynamic response to single oral doses (0.5 mg and 1.0 mg) have been compared in young and elderly healthy volunteers. No difference between the groups in peak plasma concentration (Cmax) or in the time to peak (tmax) was found, but the elimination half-life t1/2,z and area under the plasma concentration-time curve (AUC) were significantly greater in the elderly group. The immediate effects of loprazolam on all three performance tests used (postural sway, critical flicker fusion threshold (CFFT) and choice reaction time (CRT] and on subjective sedation tended to be more pronounced in the elderly subjects, though intersubject variability in response was high in both groups. The corresponding plasma concentrations did not differ significantly between the two groups. The higher (1.0 mg) dosage was associated with significant residual (11 h) impairment of standing steadiness in the elderly subjects. No other hangover effects were observed. The results are compatible with previous evidence of increased 'sensitivity' to benzodiazepines in the elderly and suggest that a lower (0.5 mg) starting dose of loprazolam would be appropriate for older recipients. Further investigation would be necessary to establish whether clinically relevant accumulation of loprazolam occurs in the elderly following repeated dosage.

Responsiveness to oral diazepam in the elderly: relationship to total and free plasma concentrations

The immediate and residual response to single doses of oral diazepam 10 mg was measured in 11 young and 12 elderly healthy volunteers using postural sway, digit symbol substitution scores and subjective ratings. The effect on postural sway was markedly accentuated in the older volunteers, but the difference between groups in the effect on the other measures used did not achieve significance. The corresponding plasma total diazepam concentrations were lower in the older subjects beyond 0.5 h post dose and the concentrations of plasma desmethyldiazepam did not differ between the groups. Diazepam plasma protein binding was significantly reduced in the elderly subjects, but the plasma free (unbound) diazepam concentrations did not exceed those in the young group. There was poor correlation between the responses measured and the concentrations of either total diazepam, desmethyldiazepam or free diazepam. The results suggest the occurrence of a non-uniform effect of age on different aspects of benzodiazepine response, and that where an accentuated effect occurs the mechanisms are substantially pharmacodynamic.

Benzodiazepines impair smooth pursuit eye movements

Five healthy male volunteers received single oral doses of 10 mg diazepam, 20 mg temazepam and placebo, in a double-blind, randomised fashion. Smooth pursuit eye movement velocity and serum benzodiazepine concentration were measured before and after at 0.5,1,1.5,2,3,4,6,9 and 12 h after administration of the treatments. Significant decrease in smooth pursuit eye movement velocity as compared to placebo was observed between 0.5-2 h after temazepam, and between 1-2 h after diazepam. Smooth pursuit eye movement velocity was log-linearly correlated with serum temazepam and diazepam concentration. The results demonstrate the relationship between serum benzodiazepine concentration and its effect on an objective measure of oculomotor performance.

Aging and drug disposition--pharmacodynamics

The pharmacodynamics of a drug is defined as the effect of the drug on physiological functions and pathological processes and can be modified in the elderly by (a) pharmacokinetics, (b) receptor sensitivity (or density), (c) impaired homeostasis or (d) pathology. The alterations in pharmacokinetics in the elderly often result in a reduction of the dose required to achieve the optimum pharmacodynamic effect. Changes in the sensitivity of receptors may be decreased in the elderly (perhaps by a diminution in the number of receptors) as in the case of the beta-adrenergic blockers, but increase in sensitivity may also be found as in the case of warfarin. Impairment of homeostatic mechanisms, while related to aging, are frequently produced by pathological processes and have an important influence on the pharmacodynamics of many drugs. The effect of the multiple pathology often found in the elderly is likely to be the dominant factor in changes in pharmacodynamics in this population. The interaction of the above factors results in a heterogeneity of pharmacodynamic response in the elderly which requires the careful monitoring of both the efficacy and toxicity of their drug treatment.

Temazepam (Restoril, Sandoz Pharmaceuticals)

Temazepam is a benzodiazepine derivative indicated for the treatment of insomnia. Pharmacokinetic studies of the hard capsule formulation indicate that the mean time to peak is 2.99 hours and the mean elimination half-life is 14.7 hours. Sleep laboratory studies have demonstrated improvements in all sleep parameters except sleep onset latency. Clinically, patients report improvements in all sleep parameters including sleep onset latency. The efficacy of temazepam compares favorably with barbiturates, glutethimide, nitrazepam, lorazepam, oxazepam, and flurazepam. It has not been compared with diazepam in the clinical setting. Side effects include drowsiness, dizziness, and lethargy. The incidence of hangover effects from 15- and 30-mg doses is relatively low. Temazepam has no proven advantages over other benzodiazepine hypnotics. The major issues that need further clarification include temazepam's sleep induction properties and the relative incidence of hangover and rebound insomnia when compared with longer-acting benzodiazepines.

Sedative-hypnotics and human performance

In 52 studies, performance data were obtained the next day following bedtime ingestion of a sedative-hypnotic or a placebo. Only eight of these studies used insomniac patients. Most studies used young adult males. Benzodiazepine hypnotics were most frequently administered and psychomotor performance was most often measured. Little consistent data are available on cognitive functioning and more complex behavior. Drug-related improvement in performance was not found, and, in comparing active drug to placebo, it is clear that all hypnotics, at some doses, produce decrements in performance the next day. Higher doses consistently showed a decrement, and this decrement was usually persistent over the entire day. Although long-acting drugs generally showed more performance decrement, half-life data were not consistent.

The relationship between peak velocity of saccadic eye movements and serum benzodiazepine concentration

1 Six healthy male volunteers received single oral doses of 10 mg diazepam, 20 mg temazepam, 15 mg flurazepam, 5 mg nitrazepam, 10 mg desmethyl-diazepam and placebo in a double-blind randomized fashion. 2 Peak velocity of saccadic eye movements, serum benzodiazepine concentration, and subjective ratings of wakefulness and co-ordination were measured at intervals up to 12 h after drug administration. 3 All active treatments produced a statistically significant decrease in peak saccadic velocity. The effect of temazepam and diazepam was generally more pronounced than that of flurazepam, nitrazepam and desmethyl-diazepam. 4 There were log-linear correlations between peak saccadic velocity and serum benzodiazepine concentration after ingestion of temazepam, diazepam and nitrazepam. 5 These results demonstrate a clear relationship between serum benzodiazepine concentration and its effect on a convenient measure of brainstem reticular formation function.

Diazepam and driving ability

A review of the literature indicates that neither experimental nor epidemiological studies can give a clear indication as to whether orally administered diazepam adversely affects the ability of a patient to drive a car. It is preferable for anxious, aggressive, or depressed patients not to drive. Since diazepam tends to relieve these symptoms, this particular medication should not lead to an automatic prohibition of car driving. Patients should always be urged to use great care while at the wheel of a motor car.

Temazepam: a review of its pharmacological properties and therapeutic efficacy as an hypnotic

Temazepam is a benzodiazepine drug which is a minor metabolite of diazepam. In clinical studies using subjective evaluation methods it was effective for maintaining sleep and increasing total sleep time. However, sleep laboratory studies did not show a significant effect on some sleep parameters, especially sleep induction. Temazepam has a relatively short half-life (about 5 to 11 hours, longer in some subjects and in the elderly), and no active metabolites of clinical importance, and thus may be considered more suitable for use as an hypnotic than longer acting drugs such as diazepam, nitrazepam or flurazepam when residual sedative effects the next day are not desirable. Indeed, few residual effects on morning performance appear to occur with usual single doses of temazepam, although at the upper end of the recommended dosage range (30 mg or more) some evidence of impaired psychomoter and cognitive function in the morning has been reported. Whether or not temazepam is likely to produce "hangover" with repeated night-time administration needs further clarification. While a call for a large number of controlled trials may not be justifiable in evaluating a new hypnotic, a few well designed additional comparative studies in insomniac subjects are needed to assess adequately the relative merits of temazepam (particularly with regard to sleep onset) compared with other benzodiazepine hypnotics, especially those which are short- or intermediate-acting.

The use of short- and long-acting hypnotics in clinical medicine

1 Activity of short- and long-acting benzodiazepines is reviewed with reference to pharmacokinetics and residual sequelae, and to efficacy and adverse effects. 2 Some benzodiazepines may not lead to obvious effects on performance, such as nordiazepam and clobazam, and the persistence of residual sequelae may not relate obviously to elimination half-lives (as with diazepam and possibly flunitrazepam). However, benzodiazepines with mean half-lives less than 8 h may have residual sequelae, whereas hypnotics with mean half-lives greater than 16 h are likely to lead to impared performance and/or anxiolytic effects the next day. 3 Potassium chlorazepate 15 mg, with its long-acting metabolite nordiazepam, would seem to be the drug of choice for insomnia secondary to anxiety. For the insomniac without significant psychopathology, temazepam 10-20 mg, triazolam 0.125-0.25 mg and for occasional use, diazepam 5-10 mg, provide the initial approach. Flurazepam hydrochloride 15-30 mg, nitrazepam 5-10 mg and flunitrazepam 1 mg and above, have persistent residual effects and should be reserved for refractory patients, and for those in whom some impairment of performance the next day would be acceptable. 4 There is little or no evidence to suggest that the proper use of the short-acting hypnotics, triazolam and temazepam, leads to a worsening of sleep on withdrawal. However, some benzodiazepines may lead to disturbances of sleep and/or rebound insomnia, and nitrazepam and flunitrazepam may be implicated.

Efficacy of some benzodiazepines for day-time sleep

1 Effects of flunitrazepam (0.25-0.50 mg) and the 1,4-triazolodiazepines, triazolam (0.25-0.50 mg) and brotizolam (0.3-0.6 mg), on day time sleep were studied by electroencephalography. 2 Flunitrazepam (0.25-0.50 mg) and triazolam (0.25-0.50 mg) reduced awake activity (P < 0.05) and improved the sleep efficiency index (P < 0.05). The higher dose of each drug increased total sleep time (P < 0.05 and < 0.01 respectively) and duration of stage 2 sleep (P < 0.01), and also delayed the first REM period (P < 0.05 and < 0.01 respectively). 3 Brotizolam (0.6 mg) markedly increased total sleep time (P < 0.001) and the sleep efficiency index (P < 0.01), and prolonged stages 2 (P < 0.01 and slow wave (P < 0.01) sleep. Over the dose range 0.3-0.6 mg, the latency to stage 3 sleep was shortened (P < 0.05), and that to the first REM period lengthened (P < 0.05). 4 All three drugs improved day time sleep. However the present observations and data from previous studies suggest that flunitrazepam (0.25-0.50 mg) may be particularly appropriate for sleep at unusual times.

Activity of the hypnotics, flunitrazepam and triazolam, in man

1 Effects of flunitrazepam and triazolam (0.25 and 0.5 mg) on sleep and on performance were studied in six healthy adult males. Sleep was assessed by electroencephalography and analogue scales, and performance by a visuo-motor coordination task.

2 Over the same dose range triazolam had a more pronounced effect than flunitrazepam. Total sleep time was increased by 0.25 and 0.5 mg triazolam, and by 0.5 mg flunitrazepam. Both drugs decreased awake activity and drowsy sleep, though the effect of flunitrazepam was limited to the 0.5 mg dose and restricted to the first 6 h after sleep onset. There were no changes in slow wave sleep.

3 Latency to the first period of rapid eye movement (REM) sleep was increased with 0.5 mg triazolam, and when doses were combined (0.25-0.5 mg) the latencies with both drugs were increased. Both doses of triazolam reduced the duration and percentage of REM sleep during the early part of the night, though the whole night duration of REM sleep was not changed.

4 After the morning ingestion of 0.25 mg flunitrazepam performance was impaired for 2.0 h, but there were no residual effects when 0.25 or 0.5 mg were taken at night. With the morning ingestion of 0.25 mg triazolam performance was impaired from 0.5 to at least 5.0 h after ingestion. There were no residual effects with 0.25 mg overnight, but with 0.5 mg triazolam there was an effect on performance 10 h after ingestion with recovery within 1.5 h (11.5 h of ingestion).

5 Triazolam (0.25 mg) and 0.5 mg flunitrazepam provide useful hypnotic activity when impaired performance the next day is to be avoided. The activity of 0.5 mg triazolam is accompanied by only limited residual sequelae compared with some other benzodiazepines of comparable efficacy, and so may prove to be useful when a more powerful effect is required.

Drugs, alcohol and driving

Driving a car is a complex psychomotor and perceptual task which is subject to impairment by many factors. Several workers have studied the potential effects of drugs and alchol in crash production by epidemiological and laboratory studies. Both types of studies have yielded useful data but their limitations must be borne in mind when applying the results in pratice. Alcohol is obviously the most common single cause of traffic accidents. A progessively increased risk with increasing blood alcohol levels is well documented; fatigue and/or drugs increase this risk. Drugs are related much more infrequently to traffic accidents although on the basis of statistics, there is a potential risk with drug use. However, drugs alone are not as important as alcohol. The most significant drugs as regards driving risk are obviously certain antianxiety agents, hypnotics, stimulants, hallucinogens, marihuana, lithium and narcotic analgesics, as well as ganglionic blocking agents, insulin and sulphonylurea derivates. Patients should not drive after taking these drug until they are objectively fully alert and capable. Anticholinergics, antihistamines, antidepressants, antipsychotics, phenybutazone, indomethacin, alpha-methyldopa, and beta-blockers may in some cases cause central side effects (e.g. drowsiness) strong enough to affect driving performance. After starting therapy with these drugs, or after a significant change in dose, driving should be avoided until it is known that unwanted effects do not occur. Psychotropic drugs may enhance the deleterious effect of alcohol, and with most hypnotics there is still an effect the next morning. Some drugs (e.g. anticonvulsants or antiparkinsonian drugs) may make driving safer, but the disease (epilepsy, Parkinsonism, cardiovascular diseases, psychic disorders, etc.) ofter precludes driving. Clinicians should warn their patients about an impairment of driving skills if this is likely to occur due to the drug or the illness concerned.

Acute effects of temazepam and nitrazepam on psychomotor skills and memory

Twelve pretrained students ingested temazepam, nitrazepam, and placebo, each double blind at one-week intervals in randomized order. Reactive and co-ordinative skills and critical flicker fusion were measured before each drug intake and 1, 2, 3, 6 and 8 hours after it. Short-term memory and paired association learning were measured at 1, 3 and 8 hours. The psychomotor responses to drugs were modified by a sequence effect (not at zero tests) which effect varied depending on the drug and parameter. In multivariance analysis it was included to reveal drug effects. Nitrazepam 10 mg increased reaction and co-ordination errors and also impaired learning and memory. Temazepam 10 mg impaired co-ordinative skills; on a whole it differed from nitrazepam but hardly from placebo. Temazepam 20 mg impaired co-ordination, and learning and memory. Both temazepam 20 mg and nitrazepam were experienced sedative. All drug effects were clearest during the first 3 hours, nitrazepam also impaired learning at 8 hours. Temazepam 20 mg seems suitable as a hypnotic.

Diazepam and 3-hydroxydiazepam (temazepam) and sleep of middle age

1 Effect of diazepam (5 and 10 mg) and temazepam (10, 20 and 30 mg) on the sleep of six healthy middle aged (45-55 years) males was studied using electroencephalography for sleep measures, and analogue scales for subjective assessments of well being and sleep quality.

2 In placebo studies the sleep of the group was compared with that of young adults (20-29 years). In the older group there was a marked reduction in total sleep time (P < 0.01), an increase in latency to stage 3 sleep (P < 0.01), and an increase in percentage of stage 1 (drowsy) and stage 2 sleep (P < 0.05 and 0.001 respectively). There were no changes in percentage or latency of rapid eye movement sleep.

3 With the middle aged group there was no increase in total sleep time with diazepam and temazepam. Sleep onset latencies were shortened by 5 and 10 mg diazepam (P < 0.05), but there was no change with temazepam. Number of awakenings was reduced by 30 mg temazepam (P < 0.01), and the duration of awakenings was reduced by 5 and 10 mg diazepam (P < 0.05) and by 20 and 30 mg temazepam (P < 0.01). Awake activity was reduced by 5 and 10 mg diazepam (P < 0.001) and by 10 mg (P < 0.05) and 20 and 30 mg (P < 0.001) temazepam. The subjects assessed their sleep as improved with diazepam and with temazepam without residual effects on well-being.

4 Though the effect of diazepam (5-10 mg) and temazepam (10-20 mg) may not be so pronounced as that of other hypnotics, they are likely to be useful over an age range which includes, at least, young adulthood and late middle age. A particular advantage of these drugs is that within these dose ranges they are without residual effects on performance.

Differential effects of the 1,4 and 1,5 benzodiazepines on performance in healthy man

1 The immediate and residual effects on performance of benzodiazepines differ, and the differences are important in the use of these drugs. 2. Diazepam and its hydroxylated metabolites, temazepam and oxazepam, each possess hypnotic activity, and have effects on performance limited to the sleep period. The demethylated metabolite of diazepam, nordiazepam, and its precursor, potassium clorazepate, which also possess hypnotic activity, have a longer duration of action, although the next day anxiolytic effect is accompanied by only minimal effects on performance. The 1.5 benzodiazepine, clobazam, seems to have minimal immediate effects on performance. 3 Diazepam and its hydroxylated metabolites, temazepam and oxazepam, would be useful in the management of insomnia without psychopathology in those cases in which residual effects on performance must be avoided. Nordiazepam and potassium clorazepate would be appropriate for insomnia secondary to day-time anxiety, and clobazam may be useful as a day-time anxiolytic. 4 It is emphasized that more work needs to be carried out on the effects of anxiolytics on performance before one can be certain that ingestion during the day would be without any deleterious effects on skilled work.

Performance studies with antihistamines

1 Effect of four antihistamines, chlorpheniramine (4 mg), clemastine (1 mg), promethazine (10 mg) and terfenadine (60 mg), on visuo-motor coordination and on subjective assessments of performance and well-being were compared with placebo in six healthy females from 0.5--7.0 h after morning ingestion of each drug. The study was double-blind, and the doses used were believed to be equally potent in their antihistaminic activity. 2 There was impaired performance 1.5 h (P less than 0.01) after chlorpheniramine, 3.0 h (P less than 0.05) and 5.0 h (P less than 0.01) after clemastine, and 3.0 h (P less than 0.01) and 5.0 h (P less than 0.001) after promethazine. It was not possible to establish effects on performance after ingestion of terfenadine. Subjective assessments of performance were not altered. 3 The subjects as a group reported improved alertness (P less than 0.05) and improved wakefulness (P less than 0.05) 0.5 h and 3.5 h respectively after ingestion of terfenadine, and were less energetic (P less than 0.05) 7.0 h after ingestion of chlorpheniramine. There were not other consistent changes in assessments of well-being.