Duration of activity and mode of action of modafinil: Studies on sleep and wakefulness in humans

The duration of activity of modafinil was investigated in healthy male volunteers in two double-blind crossover studies. Mode of action was explored using a statistical model concerned with the relationship between total sleep duration and that of rapid eye movement (REM) sleep. Nocturnal sleep (23:00-07:00) followed by next-day performance (09:00-17:00) was studied in 12 subjects administered 100, 200, 300 mg modafinil and placebo, 0.5 h before bedtime. Performance overnight (19:00-08:45) followed by sleep (09:15-15:15) was studied in nine subjects administered 100, 200, 300, 400 mg modafinil, 300 mg caffeine and placebo at 22:15. Modafinil dose-dependently reduced sleep duration (nocturnal: 200 mg, p<0.05; 300 mg, p<0.001; morning: 300 and 400 mg, p<0.05) and REM sleep (nocturnal: 300 mg; morning: 400 mg; p<0.05). The statistical model revealed that reduced REM sleep was due to alerting activity, with no evidence of direct suppression of REM sleep, suggesting dopaminergic activity. Enhanced performance with modafinil during overnight work varied with dose (200 mg>100 mg; 300, 400 mg>200, 100 mg, caffeine). However, in the study of next-day performance, the enhancement was attenuated at the highest dose (300 mg) by the greater disturbance of prior sleep. These findings indicate that modafinil has a long duration of action, with alerting properties arising predominantly from dopaminergic activity.

Human performance after a barbiturate (heptabarbitone)

1 The residual effects of heptabarbitone given overnight were studied by an adaptive tracking technique. Decrements in performance were observed at the 10 h interval after 200 mg, at the 10 h and 13 h intervals after 300 mg and at the 10 h, 13 h, 16 h and 19 h intervals after 400 mg of the drug. Decrements in performance at each interval and the persistence of the effects were dose related. 2 Subjective assessments of performance correlated with measured performance, but the subjects, as a group, over-estimated their performance after placebo and heptabarbitone. With heptabarbitone (400 mg) highly significant decrements in performance persisted to the 19 h interval after ingestion, but subjective assessments of performance to the 19 h interval did not differ significantly from subjective assessments of control activity of the day before. 3 Individual blood concentrations of heptabarbitone did not give a significant correlation with individual performance decrements, though the blood concentrations and performance decrements at each dose were related.

Effect of diazepam and fosazepam (a soluble derivative of diazepam) on sleep in man

The effect of diazepam (5 mg and 10 mg), and fosazepam (60 mg and 80 mg), a soluble derivative of diazepam, on sleep was studied in six healthy adult males using electroencephalography for sleep measures, and analogue scales for subjective assessments of well-being and sleep quality. The effect of diazepam was limited to the night of ingestion, but the effect of fosazepam was carried over to the next night and so modified sleep for about 30 h after ingestion. Effects on total sleep time were limited to the night of ingestion. There were increases with diazepam (10 mg) (P = 0.05), and with fosazepam (60 mg and 80 mg) (P = 0.001). For the night of ingestion sleep onset latencies were shortened, and awakenings were reduced by both drugs. The latency to stage 3 was shortened by fosazepam (60 mg and 80 mg) (P = 0.05). The low and high dose of each drug reduced the duration (min) of stage 0 sleep (P = 0.01), but fosazepam also reduced the duration (min) of stage 1 sleep (P = 0.001), and there was an increase in stage 2 sleep (P = 0.01). With fosazepam there were carry over effects to the next night with reduction of stage 1 sleep (P = 0.05). There were no effects on the duration of stage 3, but there was evidence that stage 4 activity was reduced during the recovery night after ingestion of fosazepam (80 mg). No effects were observed on REM sleep. Subjects reported an improved sense of well-being during the day after ingestion of diazepam and fosazepam, and with fosazepam they reported improved sleep. Correlations were calculated for sleep measures and subjective assessments.

Effect of a metabolite of diazepam, 3-hydroxydiazepam (temazepam), on sleep in man

The effect of 3-hydroxydiazepam (temazepam, 10 mg and 20 mg) on sleep was studied in six healthy adult males using electroencephalography for sleep measures, and analogue scales for subjective assessments of well-being and sleep quality. The effects were compared with diazepam (5 mg and 10 mg). Effect on total sleep time was restricted to the night of ingestion. There was no change in total sleep time after temazepam (10 mg), but with 20 mg total sleep time was increased (P = 0.01). Sleep onset latencies and awakenings were markedly reduced. Temazepam reduced the duration (min) of stage 0 (P = 0.05) and stage 1 (P = 0.01) sleep, and the effect on stage 1 was seen during each two hourly interval of sleep (P = 0.05). No effects were observed with stage 3, 3+4 and REM sleep, except that the appearance of the first REM period was delayed with temazepam (20 mg) (P = 0.001). The subjects, as a group, reported improved sleep, but subjective assessments of well-being were not altered. Correlations were calculated for sleep measures and subjective assessments.

Antihypertensive therapy in critical occupations: studies with an angiotensin II antagonist

OBJECTIVE

This study was performed to establish whether an angiotensin II antagonist modulates daytime sleepiness or performance.

METHODS

The central effects of losartan (50 and 100 mg), as well as amlodipine (5 and 10 mg) and promethazine (10 mg), were studied in six healthy volunteers (aged between 20 and 27 (mean 24) yr). Digit symbol substitution, tracking, vigilance, immediate and short-term memory recall, complex reaction time, together with objective (daytime sleep latencies) and subjective measures of sleepiness, were measured 1.0 h before and 0.5, 2.0, 3.5, 5.0, 6.5, and 8.0 h after ingestion. The study was placebo-controlled and double-blind with a six-way crossover design.

RESULTS

No changes in performance or in measurements related to sleepiness were observed with losartan (50 and 100 mg). Amlodipine (10 mg) impaired immediate memory and increased subjective sleepiness at 8.0 h (p < 0.05). Promethazine (10 mg) impaired vigilance and immediate memory recall and increased reaction time (basic and complex) from 2.0 to 6.5 h after ingestion, impaired tracking from 3.5 to 6.5 h and increased subjective sleepiness from 2.0 to 8.0 h (p < 0.05).

CONCLUSION

The study suggests that an angiotensin II antagonist could prove useful for the treatment of hypertension in aircrew.

Hypnotic activity of melatonin

OBJECTIVE

To establish the effect of melatonin upon nocturnal and evening sleep.

METHODS

Experiment I: The effect of melatonin (0.1, 0.5, 1.0, 5.0, and 10 mg), ingested at 23:30, was studied on nocturnal sleep (23:30-07:30) and core body temperature in 8 healthy volunteers. Performance was measured 8.5 h post-ingestion. On completion of the experiment dim light melatonin onsets (DLMO) were determined. Experiment II: The effect of melatonin (0.5, 1.0, 5.0, and 10 mg), ingested at 18:00, was studied on evening sleep (18:00-24:00) and core body temperature in 6 healthy volunteers. Performance was measured 6.5 h post-ingestion. Each experiment was placebo-controlled and double-blind with a cross-over design with temazepam (20 mg) as an active control.

RESULTS

Experiment I: Melatonin (5 mg) reduced the duration of stage 3 in the first 100 min of sleep. Melatonin (0.1 mg) reduced body temperature 6.5 to 7 h post-ingestion. Temazepam increased stage 2, reduced wakefulness and stage 1, and increased the latency to REM sleep. Temazepam reduced body temperature 4.5 to 6.5 h post-ingestion. There were no changes in performance compared with placebo. DLMO occurred between 20:40 and 23:15. Experiment II: Melatonin (all doses) increased total sleep time (TST), sleep efficiency index (SEI) and stage 2, and reduced wakefulness. Temazepam increased TST, SEI, stage 2 and slow-wave sleep, and reduced wakefulness. There were no changes in body temperature or performance compared with placebo.

CONCLUSION

Melatonin given at 23:30 has no significant clinical effect on nocturnal sleep in healthy individuals. Hypnotic activity of melatonin when given in the early evening (presumably in the absence of endogenous melatonin) is similar to 20 mg temazepam.

Antihistamines and aircrew: usefulness of fexofenadine

INTRODUCTION

The aim of this study was to establish whether fexofenadine hydrochloride, an antihistamine, modulates daytime sleepiness or performance.

METHODS

The effects of fexofenadine (120, 180, and 240 mg) on digit symbol substitution, tracking, and vigilance tasks, and on objective (multiple sleep latency test) and subjective sleepiness, were studied in six healthy volunteers (two males, four females, aged 20-34 [mean 26.5] yr) from 1 h pre-ingestion to 8 h post-ingestion. The study was placebo-controlled and double-blind with a six-way cross-over design. The centrally acting antihistamine, promethazine (10 mg), was used as an active control to confirm the sensitivity of the experimental procedures.

RESULTS

There were no changes in performance or sleepiness with any dose of fexofenadine at any time, compared with placebo. Promethazine, compared with both placebo and fexofenadine, impaired performance on the digit symbol substitution task (2.5 h post-ingestion), vigilance task (2.5-5h post-ingestion) and tracking task (2.5-3.5 h post-ingestion), increased objective sleepiness (1.5-2.5 h post-ingestion) and subjective sleepiness (1.5-8h post-ingestion).

CONCLUSION

Consideration may be given to the clinical use of currently licensed doses of fexofenadine (120-180 mg) by individuals involved in skilled activity. Fexofenadine may be potentially useful for aircrew.

Intensive and sustained air operations: potential use of the stimulant, pemoline

BACKGROUND

Intensive and sustained military operations involve long periods of overnight work and the occasional use of a stimulant to maintain performance may be beneficial. In this context a dose response study was carried out to investigate the effects of pemoline, a dopamimetic agent, on overnight work and to assess potential residual effects on subsequent sleep.

METHODS

Six healthy volunteers participated in a placebo-controlled, double-blind, cross-over trial involving a 12-h period of work during which subjective alertness and performance on a range of tasks were assessed at 1.5 h intervals following ingestion at 2000 hours of pemoline (10, 20, 30 and 40 mg) and, on two occasions, placebo. The work period was preceded by a 6-h sleep period with temazepam 20 mg, and followed by a 4-h recovery sleep with no medication. All sleep periods were recorded electroencephalographically.

RESULTS

There was no difference between sleep periods preceding the work period. Subjective alertness and performance on all tasks deteriorated significantly during the work period, with the earliest impairments in performance observed at 0200 hours. Pemoline increased subjective alertness and performance on all but two tasks, compared with placebo. The onset of activity was seen 4.5 h after drug ingestion and alerting effects of 30 and 40 mg pemoline persisted beyond the work period, disturbing morning recovery sleep. Doses of 10 and 20 mg pemoline had no effect on recovery sleep.

CONCLUSION

The present studies indicate that a 20 mg dose of pemoline may be suitable for maintaining nocturnal performance without having adverse effects on recovery sleep.

Central effects of the H1-antihistamine, cetirizine

BACKGROUND

Effects of the H1-antihistamine, cetirizine, were studied on daytime alertness and performance to establish whether the drug would be suitable for use by air personnel and others involved in skilled activity.

METHODS

The investigation was carried out in six healthy volunteers, and the effects of the drug (5, 10, and 15 mg) were studied on sleep latency, subjective sleepiness, digit symbol substitution, tracking and vigilance from 0.5 h to 7.5 h after ingestion. The study was placebo-controlled and double-blind with a six-way cross-over design. Promethazine (10 mg) was used as an active control to establish the sensitivity of the experimental procedures.

RESULTS

Promethazine (10 mg) decreased the mean level of vigilance over the day, increased objective and subjective sleepiness from 1.5 to 5.5 h, and impaired tracking 5.5 h after ingestion. Cetirizine (10 and 15 mg) led to shortened sleep latencies over the day, and at 7.5 h sleep latencies were shorter with 10 mg cetirizine than with placebo. Subjective sleepiness with cetirizine was increased compared with placebo after 5 mg at 1.5 h, 10 mg at 7.5 h, and 15 mg at 5.5 h and when meaned over the day. Tracking was impaired with 5 and 15 mg cetirizine 0.5 h after ingestion.

CONCLUSION

The study failed to establish dose-response effects of cetirizine, but it is evident that cetirizine is not free of central activity over the therapeutic range, and so its use by air personnel is not recommended.

Central effects of the diuretic, bendrofluazide

1. Central effects of the diuretic, bendrofluazide (2.5, 5 and 10 mg) were studied in 12 healthy volunteers. Two placebos and an active control drug, oxazepam (15 mg), were included. Single doses were administered double-blind at 10.00 h. The effects of drugs on performance and subjective feelings were assessed before and from 1.5-2.5 and 3.5-4.5 h after ingestion, and recording of the electrical activity of the brain (EEG) and body sway carried out. 2. Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, together with critical flicker fusion and two flash fusion. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. The EEG was recorded with eyes open while the subjects carried out a mental arithmetic task, and with eyes closed, when they were required to relax. Body sway was recorded with eyes open and with eyes closed. 3. Bendrofluazide (10 mg) increased the number of errors at letter cancellation and reduced the rate of finger tapping (P < 0.05), while oxazepam increased the number of errors and reduced accuracy at continuous attention (P < 0.01), and increased the number of involuntary rest pauses during tapping (P < 0.05). 4. There were no effects of drugs on subjective assessment of mood. 5. No changes in the electrical activity of the brain were observed with bendrofluazide. In recordings with eyes open, oxazepam reduced delta (0.5-3 Hz), theta (3.5-7 Hz) and alpha 2 (10.5-13 Hz) while increasing beta 1 (13.5-21 Hz) activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Central effects of repeated administration of atenolol and captopril in healthy volunteers

The central effects of atenolol (50 mg tds) and captopril (50 mg tds) ingested for a period of seven days were studied in ten healthy volunteers. A placebo and two active control drugs, methyldopa (250 mg tds) and oxazepam (10 mg), were included in the design. Oxazepam was ingested on the seventh day only, with a placebo being taken on the preceding six days. On the seventh day, central effects of the drugs were tested at 10.00-11.00 h (session 1), immediately before the subjects' last dose of each drug and at 2.5-3.5 h after the final dose of each drug (1330-1430 h, session 2). Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, critical flicker fusion and two flash fusion. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. Recordings of the EEG and body sway were carried out. Neither atenolol nor captopril altered performance at any of the skills tested. There were no effects on subjectively assessed alertness or mood with captopril, while atenolol significantly increased wakefulness in session 2 and when the two sessions were meaned. Similarly, captopril did not modify body sway, while with atenolol there was a significant decrease in activity in the frequency range 1.0-2.75 Hz from session 1 to session 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of polar route schedules on the duty and rest patterns of aircrew

The duty and rest periods of aircrew operating the polar route from London via Anchorage were recorded during five schedules which involved 1-, 2- or 3-day sojourns in Japan. Sleep throughout each schedule was fragmented, with naps before duty and short sleeps after arrival at a new location. Sleep disturbance rather than cumulative sleep loss appeared to be the overriding problem, and the shorter schedules had the most marked disturbances in sleep during the trip and during the immediate recovery period. Electroencephalographic studies are necessary to confirm these observations, and information on circadian rhythmicity is needed to define the circumstances which lead to persistence of sleep disturbance on return to Europe.

Jet lag and motion sickness

Jet lag. Present day aircraft operating round northern and southern latitudes cross time zones at almost the same rate as the earth rotates, and it is these rapid transmeridian transitions that lead to the syndrome commonly referred to as jet lag. On arrival at their destination, individuals find themselves out of synchrony with the social and time cues of their new environment and, until they adapt, may experience symptoms such as malaise, gastrointestinal disturbance, loss of appetite, tiredness during the day and poor sleep. The severity and exact nature of the problems vary with the direction of travel and the number of time zones crossed, and some people react more unfavourably to intercontinental travel than others. Clearly, with increasing numbers of passengers undertaking such journeys, there is considerable interest in strategies to reduce the immediate effects of jet lag or to facilitate acclimatisation. Motion sickness is a generic term which embraces seasickness, airsickness, carsickness, space sickness etc, names that identify the provocative environment or vehicle. It is a normal reaction of humans to exposure to certain motion stimuli that occur during passive transportation.

Central effects of the calcium antagonist, nifedipine

1. Central effects of the calcium antagonist, nifedipine retard (10, 20 and 40 mg) and nifedipine capsules (10 mg) were studied in 14 healthy male subjects. Two placebos and an active control drug, oxazepam (15 mg), were included. Medication was administered double-blind at 10.00 h. The effects of drugs on performance and subjective feelings were assessed before and from 1.5-2.5 h and 3.5-4.5 h after ingestion, and recordings of the electrical activity of the brain (EEG) and body sway carried out. 2. Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, together with critical flicker fusion and two flash fusion. The EEG was recorded with eyes open while the subjects carried out a mental arithmetic task, and with eyes closed, when they were required to relax. Body sway was recorded with eyes open and with eyes closed. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. 3. Nifedipine did not alter performance levels on any of the skills tested, while oxazepam (15 mg) increased the number of errors (P less than 0.01) and reduced accuracy at continuous attention (P less than 0.01). 4. Nifedipine (10 mg) reduced total power of the EEG in the frequency range (0.5-30 Hz), and nifedipine (20 mg) increased total alpha power (7.5-13 Hz) (P less than 0.05). Oxazepam reduced alpha and increased beta 1 power (13.5-21 Hz).(ABSTRACT TRUNCATED AT 250 WORDS)

Sedation and histamine H1-receptor antagonism: studies in man with the enantiomers of chlorpheniramine and dimethindene

1. The effects of 10 mg (+)- and (-)-chlorpheniramine and 5 mg (+)- and (-)-dimethindene on daytime sleep latencies, digit symbol substitution and subjective assessments of mood and well-being were studied in 6 healthy young adult humans. Each subject also took 5 mg triprolidine hydrochloride as an active control and two placebos. 2. Daytime sleep latencies were reduced with triprolidine, (+)-chlorpheniramine and (-)-dimethindene, and subjects also reported that they felt more sleepy after (+)-chlorpheniramine and (-)-dimethindene. Performance on digit symbol substitution was impaired with (+)-chlorpheniramine. 3. Changes in measures with (-)-chlorpheniramine and (+)-dimethindene were not different from changes with placebo. 4. In the present study, changes in measures of drowsiness and performance were limited to the enantiomers with high affinity for the histamine H1-receptor. These findings strongly suggest that sedation can arise from H1-receptor antagonism alone, and provide further support for the belief that the histaminergic system is concerned with the regulation of alertness in man.

Presynaptic alpha 2-adrenoceptor function and sleep in man: studies with clonidine and idazoxan

The effects of an alpha 2-adrenoceptor agonist, clonidine and an antagonist, idazoxan, were studied on nocturnal sleep in man. Clonidine increased non-rapid eye movement sleep and idazoxan reduced slow wave sleep and increased awake activity. Changes in the continuity of sleep with clonidine were similar to, and those with idazoxan opposite to, the effects of maprotiline, an inhibitor of the uptake of noradrenaline, used as an active control. These findings support the previous conclusion that raised levels of noradrenaline in the synapse, after inhibition of uptake, lead to increased presynaptic inhibition of release of transmitter in man. However, all three drugs decreased rapid eye movement (REM) sleep and the ratio of REM to nonREM sleep and this is believed to be due to a non-specific upset of the balance of influences which control the appearance of REM sleep.

Circadian rhythmicity and sleep of aircrew during polar schedules

Sleep and circadian rhythms of aircrew were studied during a 7-d polar schedule operated between London and Tokyo. Sleep, rectal temperature, and subjective alertness were recorded for 2 d before departure during the schedule, and for 10 d after the return. Changes in sleep during the early part of the trip were due to sleep loss on the outward journey, but later these changes were related to the displacement of the circadian rhythm. The acrophases of the circadian rhythms of temperature were delayed by the outward journey, and amplitudes were reduced throughout the trip. During the return, aircrew reported high levels of tiredness which persisted until the second recovery night. Though the amounts of sleep obtained during the schedule were satisfactory for the aircrew as a group, some crewmembers experienced difficulties. Realignment of circadian rhythms was attained by an advance of the circadian phase in eight aircrew and by a delay in three, and resynchronization was achieved in all cases within 6 d.

Central effects of the angiotensin-converting enzyme inhibitor, captopril. II. Electroencephalogram and body sway

1. Effects of single doses of captopril (12.5, 25 and 50 mg) on the electroencephalogram (EEG) and on body sway were studied in fourteen healthy male subjects. Oxazepam (15 mg), as an active control, and two placebos were included in the study, together with a single dose of atenolol (100 mg). Medication was administered double-blind at 11.00 h, and assessments made before and at 2 and 4 h after drug ingestion. 2. There were no changes in the EEG with captopril. Oxazepam reduced the circadian rise in alpha activity, while atenolol decreased beta power. Delta activity was modified by both oxazepam and atenolol. 3. A reduction in lower frequencies of body sway (0.05-1 Hz) occurred with captopril, while the spectra were unaffected by oxazepam. Atenolol increased (P less than 0.05) activity in the frequency range 0.75-2.75 Hz. 4. These observations suggest that captopril is free of central effects such as sedation that may occur with beta-adrenoceptor antagonists. Reduced body sway with captopril could reflect improved integration of central and peripheral control of posture.

Central effects of the angiotensin-converting enzyme inhibitor, captopril. I. Performance and subjective assessments of mood

1. Central effects of single doses of captopril (12.5, 25 and 50 mg) were studied in fourteen healthy male subjects. Two placebos and an active control drug, oxazepam (15 mg), were included, together with a single dose of atenolol (100 mg). The drugs were administered double-blind at 11.00 h, and performance and subjective feelings were assessed before and from 1.5-2.5 h and 3.5-4.5 h after ingestion. 2. Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, together with critical flicker fusion and two flash fusion. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. 3. Captopril did not impair performance on any of the tests, but improved short-term memory (P less than 0.05) and increased the number of letters cancelled (P less than 0.05). Oxazepam reduced the number of substitutions completed in the digit symbol test (P less than 0.01), accuracy on continuous attention (P less than 0.05), number of letters cancelled (P less than 0.05), and rate of finger tapping (P less than 0.05), and increased choice reaction time (P less than 0.001). Atenolol reduced the rate of finger tapping (P less than 0.05), but increased the number of letters cancelled (P less than 0.05). 4. No effects on mood or on subjective feelings were evident with captopril. Oxazepam reduced subjective alertness (P less than 0.05), and atenolol increased feelings of sleepiness (P less than 0.05). 5. Although these observations suggest that central effects may exist with captopril, no adverse consequences have been established on performance or on subjective assessment of mood. Captopril may, therefore, be an appropriate drug for hypertensive patients engaged in skilled activity.

Medication and skilled work

There is increasing interest in the way in which drugs impair performance. This has arisen because some may impair day-to-day skills of those whose occupations demand vigilance and motor skill, and of those who are involved in decision making or where interpersonal relations are crucial. For many years the position was adopted, at least in certain occupations where impaired performance could be a danger to others, that the use of any drug should preclude employment. However, recent advances in therapeutics and a greater understanding of drug action in man has made this rather uncomplicated view of life less tenable, and there is now an increasing desire that advances in therapy should, if at all possible, be available to occupational groups, such as airline pilots. In this way the adverse effect which a drug may have on performance has become an important aspect of its clinical profile. Hypnotics appropriate for transient insomnia, which may arise from the irregularity of rest inherent in many occupations, need to be free of residual effects, antihistamines that are sedative must be avoided, and drugs used in the management of mild hypertension, often during the important years of middle life, must be as free as possible from central effects. And it must be emphasized that these drugs are often used by active, healthy or near healthy individuals. The issues involved in the safe use of a particular drug by a particular individual are complex, and as with all aspects of therapeutics it is sometimes necessary to balance efficacy and adverse effects.

Hypnotics and occupational medicine

The appropriate use of hypnotics requires an understanding of the nature of the patient's insomnia and lifestyle. In the context of occupational medicine, the potential effects of these drugs on job skills and the persistence of such effects are also important considerations. This report reviews the factors that must be considered in the investigation of impaired performance due to hypnotics and the pharmacokinetic properties that determine the persistence of action of these drugs. Sleep disturbance associated with transmeridian flights (jet lag) is used to illustrate the place of hypnotics in the management of a transient form of insomnia.

Dopaminergic transmission and the sleep-wakefulness continuum in man

Modulation of dopaminergic transmission on daytime alertness and performance and on nocturnal sleep were studied in man using 30, 60 and 90 mg pemoline, a dopamimetic drug, and 2, 4 and 6 mg pimozide, a dopamine receptor antagonist. Pemoline lengthened daytime sleep latencies and improved attention, and increased wakefulness during nocturnal sleep. Rapid eye movement (REM) sleep was reduced with 90 mg pemoline, but this was due entirely to increased wakefulness. Pimozide had little effect on overnight sleep, but increased the tendency to fall asleep and impaired performance during the day. These studies suggest that the effects of certain drugs which modulate the activity of neurotransmitters, involved in the control of sleep and wakefulness, may be related to the inherent level of activity of the central nervous system. Modulation of the dopaminergic system can have a profound influence on the manifestation of wakefulness and vigilance, but is unlikely to modify directly the elaboration of REM sleep in man.

Modulation of rapid eye movement sleep in humans by drugs that modify monoaminergic and purinergic transmission

Modulation of rapid eye movement (REM) sleep is a well-established effect of many centrally acting drugs. However, there is uncertainty concerning the nature of the changes and their significance, and it is in this context that we have analyzed the effects of several groups of drugs that alter monoaminergic or purinergic transmission on sleep in humans. The analysis shows that drugs that modulate noradrenergic and serotonergic transmission lead to marked suppression of REM sleep, irrespective of any increase or decrease in sleep duration. There is no evidence that the timing of the ultradian cycle of REM sleep relative to sleep onset is altered by these drugs. On the other hand, reduced REM sleep with dopamimetic drugs is due solely to increased wakefulness. However, there can be more subtle effects of some drugs on REM sleep. Benzodiazepine receptor agonists and drugs that modify purinergic transmission modulate the appearance of early REM activity. There may, therefore, be two discrete systems that control entry into REM sleep, and that are responsive to drugs. The exact appearance and timing of REM periods may be modulated by a feedback mechanism involving GABAergic, or possibly purinergic, transmission, while monoaminergic and cholinergic influences exert a reciprocal and overriding control of REM sleep.

Modulation of sleep by trimipramine in man

We have studied the acute effect of trimipramine (25, 50 and 75 mg) on nocturnal sleep in 6 young men. Fluoxetine (60 mg) and diazepam (10 mg) were included as controls for the potential changes in sleep measures. Trimipramine reduced awake activity, Stage 1 (drowsy) sleep, and the duration of rapid eye movement (REM) sleep. Non-REM (Stage 2) sleep was increased. Residual effects of trimipramine were present the next morning (9 h after ingestion) with impaired coding ability. The effects of trimipramine on sleep and daytime alertness are consistent with its complex pharmacological profile. Reduced wakefulness and sedation are most likely due to synergism between histamine H1, alpha 1-adrenoceptor, and dopamine receptor antagonism. Anticholinergic activity and possibly blockade of alpha 1-adrenoceptors would disturb the balance of transmitter activities which facilitates the optimal appearance of REM sleep. In this way the effects of trimipramine on nocturnal wakefulness and REM sleep are similar to drugs which inhibit the uptake of noradrenaline.

Rapid eye movement sleep and sleep continuity. Depression and antidepressants

Abnormalities of sleep and mood occur in depressive illness, and both disturbances may respond to therapy. Antidepressant drugs of all classes bring about immediate and often pronounced changes in sleep. Some drugs reduce, whereas others increase, nocturnal wakefulness, but most, if not all, suppress rapid eye movement activity, although it is uncertain whether this is linked directly to elevation of mood. Such changes in sleep continuity are related to the individual pharmacological profile of drugs, and in some instances, such as with trimipramine, may arise from the interaction of properties which alone may not lead to marked effects on sleep. On the other hand, inhibition of REM sleep appears to be related to a nonspecific disturbance of the balance between monoaminergic and cholinergic influences. In this way, REM sleep is reduced not only with drugs which selectively modulate noradrenaline or serotonin activity, but also with drugs which have complex pharmacological profiles.

Central effects of beta-adrenoceptor antagonists. I--Performance and subjective assessments of mood

1. Central effects of the beta-adrenoceptor antagonists, propranolol (40, 80 and 160 mg) and atenolol (50 and 100 mg) were studied in 12 healthy male subjects. Two placebo ingestions and an active control (oxazepam 15 mg) were included. Single doses were administered double-blind at 11.00 h, and assessments of performance and subjective feelings were made before, 2 h and 4 h after ingestion. 2. Performance was measured using letter cancellation, digit symbol substitution, continuous attention, choice reaction time, finger tapping, short term and immediate memory, critical flicker fusion and two flash fusion. Subjective feelings were assessed using twelve visual-analogue scales. 3. Oxazepam impaired performance at letter cancellation (P less than 0.001), digit symbol substitution (P less than 0.05), continuous attention (P less than 0.001), immediate recall (P less than 0.05) and finger tapping (P less than 0.05), but neither of the beta-adrenoceptor antagonists affected these measures. Propranolol (40 and 160 mg) also impaired short term memory (P less than 0.05), though it was not possible to establish this effect with atenolol. 4. Subjective alertness was reduced by oxazepam (P less than 0.01) and atenolol (P less than 0.05), while propranolol (40 mg) reduced anxiety (P less than 0.01) and propranolol (80 mg) impaired ability to concentrate (P less than 0.05). 5. The results suggest that both lipophilic and hydrophilic antagonists modify the central nervous system, though impairment may be difficult to establish with conventional tests. The observations on memory and alertness suggest that the central effect of beta-adrenoceptor antagonists may be subtle.

Central effects of beta-adrenoceptor antagonists. II--Electroencephalogram and body sway

1. Effects of the beta-adrenoceptor antagonists, propranolol (40, 80 and 160 mg) and atenolol (50 and 100 mg) on the electroencephalogram and on body sway, were studied in 12 healthy male subjects. The study was double-blind, and included two placebos and an active control, oxazepam (15 mg). Medication was ingested at 11.00 h, and assessments were made before, and at 2 h and 4 h after ingestion. 2. All doses of both beta-adrenoceptor antagonists modified the electroencephalogram, and the changes reported were statistically significant at probability levels of less than 5%. The circadian rise in alpha activity was reduced by both beta-adrenoceptor antagonists as well as by oxazepam. Atenolol also decreased beta activity. 3. Body sway was modified by atenolol and oxazepam (P less than 0.05). The increase with oxazepam was most marked in the low frequency component (0.05-2.25 Hz) of the spectrum, while atenolol modified only the component of higher frequency (2.25-4.0 Hz). 4. These observations suggest that propranolol and atenolol have a sedative effect, and that hydrophilic antagonists are unlikely to be free of central activity. The changes in body sway could imply that peripheral mechanisms may be modified at least with atenolol.

Altitude insomnia: studies during an expedition to the Himalayas

During an expedition to the Himalayas, we studied the sleep and respiration of six climbers. Three ingested acetazolamide (500 mg) daily throughout the climb and the other three ingested placebo. At high altitude (4,150-4,846 m), each subject ingested temazepam (10 mg) for one night and placebo for another. Acetazolamide improved sleep above 2,750 m, but it is uncertain whether this was due to sedation or to improvements in arterial oxygen saturation. Sleep was markedly disturbed in all subjects above 4,000 m. Temazepam improved sleep, and in subjects taking acetazolamide, it reduced sleep-onset latencies and increased sleep efficiency close to that of sea level values. These observations suggest that the prophylactic use of acetazolamide is likely to improve sleep in climbers and that a low dose of a benzodiazepine such as temazepam (10 mg) may be beneficial at high altitude. Studies are now needed to exclude any possibility of respiratory impairment at altitude before a firm recommendation can be made regarding the routine use of this hypnotic.

Studies on the modulation of the sleep-wakefulness continuum in man by fluoxetine, a 5-HT uptake inhibitor

The effects of an inhibitor of the uptake of 5-hydroxytryptamine (5-HT) fluoxetine (20, 40 and 60 mg), on nocturnal sleep and on alertness during the day, were studied in healthy adults. Fluoxetine reduced the total sleep time and the duration of rapid eye movement (REM) sleep and increased awake activity and stage 1 (drowsy) sleep during the night. Daytime sleep latencies were longer after fluoxetine but, paradoxically, the subjects felt more drowsy and coding ability was impaired. It is considered that the alerting effect of fluoxetine in man is most likely related to modulation of 5-HT-mediated transmission, whereas suppression of REM sleep is a nonspecific effect which arises when the balance of monoaminergic and cholinergic influences is disturbed. It is suggested that the serotonergic system has a pervasive influence throughout the sleep-wakefulness continuum, in contrast with some other neurotransmitter systems, which may be more concerned with the subtle manifestations of vigilance.

Rapid eye movement sleep in man: modulation by benzodiazepines

The modulation of rapid eye movement REM sleep in man by benzodiazepines has been analysed using 366 sleep recordings with at least 3 REM periods, obtained in 25 individuals, over 9 years. Sleep-dependent and sleep-independent mechanisms are believed to control REM activity, and the effect of benzodiazepines can be explained if the sleep-dependent influence is modified. It is suggested that a negative feedback mechanism, which usually encourages the appearance of REM periods, is depressed, while a threshold and oscillator which determine the cyclical appearance of the activity, and its relation with the onset of sleep, are unaffected.

1986 Stewart memorial lecture. Sleep and wakefulness of the airline pilot

There are two overriding concerns in the design of schedules for aircrew who have to cope with irregularity of their sleep due either to work at unusual times of the day or to time zone changes. The first is that aircrew must be able to achieve an acceptable sleep pattern, and this is likely to involve short periods of sleep and naps. These, in turn, depend on limits to duty hours. The second is that the arrangement of work must bear in mind that prolonged duty and duty at certain times of the day may both involve relatively low levels of performance, and modelling can identify the adverse interactions of these influences. It is also important that the quality of the sleep of the individual pilot is taken into consideration when there are undue difficulties in coping with irregularity of work.

Efficacy of zopiclone in middle age

Effects of zopiclone (5.0, 7.5, and 10 mg) on sleep and on performance were studied in middle-aged subjects. Zopiclone (5.0-10.0 mg) reduced awake activity and the number of awakenings, and increased the duration of stage 2 sleep. The appearance of REM sleep was delayed, but this effect was without reduction over the whole night. There were no impairments in the digit symbol substitution test when zopiclone was compared with placebo, although there were less substitutions with 10.0 mg than with 5.0 mg. Symbol copying and choice reaction time were unaltered. Zopiclone would appear to be a useful hypnotic for those involved in skilled work. Based on the results obtained in healthy volunteers, the 5.0 mg dose would be appropriate for many; if in insomniac patients, 7.5 mg was needed, then it is likely to be free of undue impairment of performance the next day.

Studies on the central effects of the H1-antagonist, loratadine

Effects of loratadine (10, 20 and 40 mg) on visuo-motor coordination, dynamic visual acuity, short-term memory, digit symbol substitution, and on subjective assessments of mood were tested before, and 0.5, 1.5, 3.5 and 5.5 h after ingestion by 6 healthy female adults. There were no effects of 10 or 20 mg loratadine. With 40 mg loratadine the number of substitutions on the digit symbol test was reduced 5.5 h after ingestion, and on dynamic visual acuity response time was increased at 3.5 h and the number of responses missed was increased at 5.5 h. Triprolidine (10 mg) which was used as active control impaired performance on all the tasks and impaired performance was observed at all times after ingestion. Loratadine is a promising antihistamine for individuals involved in skilled activity. The anticipated single daily dose of 10 mg is unlikely to impair performance.

Studies on performance with aspirin and paracetamol and with the centrally acting analgesics meptazinol and pentazocine

Effects of aspirin (325 and 650 mg) and paracetamol (500 and 1000 mg), and of the centrally acting analgesics meptazinol (100 and 200 mg) and pentazocine (25 and 50 mg) on visuo-motor coordination and dynamic visual acuity, together with critical flicker fusion, digit symbol substitution, complex reaction time and subjective assessments of mood, were studied from 0.75-2.0 h after ingestion by seven healthy female adults. The study was double-blind and placebo controlled, and triprolidine (10 mg) was used as the active control. No effects of meptazinol and paracetamol on performance were observed. Pentazocine (25 mg) impaired performance on digit symbol substitution (p less than 0.05) and aspirin (650 mg) appeared to have shortened complex reaction time (p less than 0.05). Meptazinol (100 mg) increased the component of mood assessments related to wakefulness (p less than 0.05). Impaired performance with pentazocine may involve opioid receptor activity, while the apparent alerting effect of meptazinol may relate to its cholinergic activity. The possible effect of aspirin on reaction time needs to be confirmed.

Irregularity of rest and activity: studies on circadian rhythmicity in man

1. Rectal temperature, electrolyte excretion and performance were studied in young adults who followed an irregular pattern of work and rest for 9 days in an isolation unit. 2. In the analysis, effects evoked by the pattern of work and rest were separated from the oscillatory component, and rhythms for individual days were examined by the cosinor method. 3. During the schedule, rhythms no longer showed a period of exactly 24 h, and this effect was confirmed by studies using a repeated cycle of irregular work and rest and by studies using constant routines. 4. Temperature and urinary constituents differed in the strength and phase of their rhythms when corrected for evoked effects, as well as in the strength of the evoked effects themselves. 5. There was evidence of deterioration in performance during work periods which exceeded 9 h, but there was no evidence of progressive deterioration in performance over the 9 day schedule.

Drugs and impaired performance

Transient insomnia is known to occur in people who normally sleep well but whose sleeping pattern has been altered (e.g. by shift-work, intercontinental travel). The occasional use of an hypnotic is likely to be beneficial in these cases although, in the past, the problem of daytime sedation precluded the use of such drugs in certain occupations. Recent advances in therapeutics reflect the increasing interest in the impairment of performance and it is now recognized that both the nature and persistence of any effect must be determined. Two broad approaches are used at present: the laboratory study of isolated skills and some form of simulation such as car handling. There is, however, clear disagreement concerning the relevance of these two methods to the real-life situation and both have their limitations, so results must be interpreted with caution. In addition, an inability to demonstrate impaired performance does not necessarily mean that the drug is completely free from adverse effects, and different effects may be seen in a patient population compared with healthy volunteers because of variations in age, gender or concomitant drug therapy etc. It is fortunate that there are many drugs within a specific group which, though they have similar efficacy, have different effects on performance and so, accepting a limited impairment of performance, it should be possible for therapy to be suited to the day-to-day needs of any individual patient.

International cooperative study of aircrew layover sleep: operational summary

The findings of this cooperative study of layover sleep have direct implications for flight operations. In the consensus view of the principal investigators, these can be divided into their relevance for eastward or westward flight. Eastward flight produced more sleep disruption than westward. Different sleep and scheduling strategies are recommended for each flight direction, and the importance of individual crewmember factors is discussed in relation to age and circadian type. Despite the limitations of this study with regard to trip simplicity and the baseline data, the results for each airline are highly consistent and should be applicable to a wide range of long-haul crewmembers and carriers.

Hypnotics and transient insomnia

An hypnotic should be used only when there is evidence of sleep disturbance. The wide range of sleep disorders (e.g. delayed sleep onset or problems of sleep maintenance) and the added complication that the patient may be involved subsequently in skilled work demand that the pharmacokinetics of various hypnotics must be understood before the correct hypnotic can be chosen. Impaired performance is more severe and persists far longer with compounds that are slowly eliminated and with the use of higher doses. The particular situations of aircrew and mountaineers have been studied in detail. Caution must be exercised in the management of aircrew coping with irregularity of rest and work. Temazepam has been used for aircrew for over 10 years and the absence of adverse effects ensures that it remains the recommended hypnotic in this area of medical practice. The relationship of insomnia with the hypoxic environment is undetermined. To investigate this, sleep was studied in six individuals during an expedition to the Himalayas. At altitude, temazepam led to less wakefulness and to drowsy sleep--there were no prolonged sleep latencies.

Nocturnal sleep and daytime alertness of aircrew after transmeridian flights

The nocturnal sleep and daytime alertness of aircrew were studied by electroencephalography and the multiple sleep latency test. After a transmeridian flight from London to San Francisco, sleep onset was faster and, although there was increased wakefulness during the second half of the night, sleep duration and efficiency over the whole night were not changed. The progressive decrease in sleep latencies observed normally in the multiple sleep latency test during the morning continued throughout the day after arrival. Of the 13 subjects, 12 took a nap of around 1-h duration in the afternoon preceding the return flight. These naps would have been encouraged by the drowsiness at this time and facilitated by the departure of the aircraft being scheduled during the early evening. An early evening departure had the further advantage that the circadian increase in vigilance expected during the early part of the day would occur during the latter part of the return flight.

Sleep after transmeridian flights

Nocturnal sleep and daytime sleep latencies, recorded electroencephalographically after westward and eastward flights across the North Atlantic involving time zone shifts of 5 h, were influenced by the time of the flight and by subsequent displacement of the rest period. After the westward flight there was sleep disturbance during the latter part of the first night. However, there was persistent disturbance of sleep after the eastward flight. A rapidly eliminated hypnotic may be useful for the first night or two after a westward flight and for a few nights after an overnight eastward flight.