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.