The effects of the sub-chronic administration of an anti-histamine, clemastine, on tests of car driving ability and psychomotor performance

Cognitive domains affected by histamine H(1)-antagonism in humans: a literature review

The neurotransmitter histamine has been suggested to be involved in cognitive functioning. Generally, studies in animals have shown a decrease in performance after decreasing histamine neurotransmission and improved performance after increasing histamine neurotransmission. It is unclear, however, what role histamine plays in cognition in humans. Up until now, most data are derived from studies and reviews that aimed to assess the sedative potential of H(1)-antagonists and not the effects on cognition in particular. The objective of this paper is specifically to review which cognitive domains are affected by H(1)-antagonists. Taken together, 90 experimental studies on the performance effects of sedative H(1)-antagonists published between 1973 and 2009 were reviewed. Results showed that psychomotor skills and attention are most frequently impaired and memory the least. Tasks assessing memory that were affected usually required rapid responses. It was concluded that both the complexity of the task as well as the demand for information processing speed determines the sensitivity to the effects of central H(1)-antagonism. The importance of the sensitive cognitive domains to histaminergic dysfunction, as well as the relation between histamine related decrease in arousal and task performance deserve further research.

Effects of a sedative antihistamine, D-chlorpheniramine, on regional cerebral perfusion and performance during simulated car driving

OBJECTIVES

The sedative side effects of antihistamines have been recognized to be potentially dangerous in car driving, but the mechanism underlying these effects has not yet been elucidated to date. The aim of the present study is to examine regional cerebral blood flow (rCBF) responses during a simulated car-driving task following oral administration of D-chlorpheniramine using positron emission tomography (PET) and [15O]H2O, based on a single-blind cross-over study-design.

METHODS

Right-handed, healthy male volunteers (n = 14) drove a car in a simulated environment following oral administration of D-chlorpheniramine repetab 6 mg or placebo. Their rCBF was measured using PET with [15O]H2O in the following three conditions: (1) resting, (2) active driving, and (3) passive driving. All 'in-car' views during the simulated driving were videotaped and used for rating driving performance.

RESULTS

Performance evaluation revealed that the number of lane deviations significantly increased in the D-chlorpheniramine condition compared with the placebo condition (p < 0.01). Subjective sleepiness was not significantly different between the two drug conditions. The regions of diminished brain responses following D-chlorpheniramine treatment were detected in the parietal, temporal and visual cortices, and in the cerebellum. The regions of augmented rCBF responses were found in the orbitofrontal cortex and cerebellar vermis.

CONCLUSION

These results suggest that D-chlorpheniramine tends to suppress visuo-spatial cognition and visuo-motor coordinating functions rather than attention and motor functions during car driving.

Sedation and antihistamines: a review of inter-drug differences using proportional impairment ratios

The use of antihistamines (AHs) has until recently been associated with a number of undesirable side effects, the most troublesome of which is sedation. There are two aspects to sedation. The first, an objectively determined measure based on the results of psychometric tests from controlled trials, and the second, the subject's response to the administration of a drug. Since AHs are largely used in ambulant patients, a complete evaluation of sedation should be performed through standardised objective and subjective tests, shown to be sensitive to the central effects of AHs.An extensive review of the literature identified 76 studies of H(1) receptor antagonists in healthy volunteers, in which assessment of sedation was the primary objective. Results from studies published in peer-reviewed journals which employed a placebo condition as well as a positive internal control using a crossover design were analysed to determine the extent to which a particular antihistamine produced impairments on a battery of psychometric tests. The impairment index for each antihistamine was calculated and subsequently compared with the impairment index obtained for all other AHs.The calculation of this proportional impairment ratio enabled the sedative potential of an individual antihistamine to be identified relative to all other AHs and thus allowed the ranking of AHs with respect to their ability to cause impairments of cognitive and psychomotor function.Findings from this review clearly demonstrate that there are distinct classes of AHs with respect to their ability to impair cognitive function and psychomotor performance. Copyright 2000 John Wiley & Sons, Ltd.

The use of microcomputer-based psychomotor tests for the evaluation of benzodiazepine effects on human performance: a review with emphasis on temazepam

1. The literature relating to the effects of benzodiazepines in general, and temazepam in particular, on human psychomotor performance as assessed using microcomputer-based testing batteries is surveyed. 2. The adverse effects of central nervous system depressants on performance is an important mediocolegal issue and frequently comes into question in on-the-road and on-the-job accidents. The use of microcomputer-based testing batteries allows for performance evaluation both in the laboratory and at-the-scene, as well as providing the opportunity to model a large number of different behaviours required in routine yet complex psychomotor tasks. 3. The conclusions in general are: (1) The benzodiazepines as a class of drugs impair both cognitive and motor performance. These effects are often subtle when low doses are involved or when testing occurs the morning following evening administration of the medication. (2) No single psychomotor task adequately simulates complex daily tasks such as automobile driving. A battery of tests that evaluates a number of the components of such tasks is necessary to determine adequately the full range of effects of these medications.

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.

Behavioural effects of histamine and its antagonists: a review

This review focuses on the behavioural effects of histamine and drugs which affect histaminergic function, particularly the H1- and H2-receptors antagonists. Research in this area has assumed considerable importance with increasing interest in the role of brain histamine, the clinical use of both H1 and H2 antagonists and evidence of nonmedical use of H1 antagonists. Results from a number of studies show that H1 and H2 antagonists have clear, but distinct subjective effects and that H1 antagonists have discriminative effects in animals. While H1 antagonists are reinforcers in certain conditions, histamine itself is a punisher. Moderate doses of H1 antagonists affect psychomotor performance in some situations, but the results are variable. The exceptions are terfenadine and astemizole, which do not seem to penetrate the blood-brain barrier readily. In studies of schedule-controlled behaviour, marked changes in response rate have been observed following administration of H1 antagonists, with the magnitude and direction dependent on the dose and the baseline behaviour. Histamine reduces avoidance responding, an effect mediated via H1-receptors. Changes in drinking and aggressive behaviour have also been observed following histamine administration and distinct roles for H1- and H2-receptors have been delineated. Separate H1- and H2-receptor mechanisms have also been suggested to account for changes in activity level. While the H2 antagonists do not always have strong behavioural effects when administered peripherally, there is evidence that cimetidine has a depressant effect on sexual function. These and other findings reveal an important role for histaminergic systems in a wide range of behaviour.

A comparison of methods for assessing the sedative effects of diphenhydramine on skills related to car driving

A double blind cross-over study was performed to compare the sensitivity of "oof road" driving with that of laboratory tests of driving-related skills to drug induced sedation. Twelve experienced drivers (6 M, 6 F) received single oral doses of the H1-antagonist diphenhydramine 25, 50 and 100 mg and placebo. Each treatment was administered on 2 separate occasions, once in the driving school when real driving skills were assessed and again in the laboratory when performance of an adaptive tracking task, body sway and visual reaction were measured. On all occasions subjects assessed their own performance and alertness/sedation using visual analogue scales. Data were subjected to analysis of variance and differences assessed by Newman Keul's test. Diphenhydramine failed to impair driving performance at any dose while all doses produced significant changes in each of the 3 laboratory tests. Subjects rated themselves sedated after all 3 doses of active drug in the laboratory but only after the 100 mg dose in the driving school. Tests performed in the psychopharmacology laboratory appear to be more sensitive to the sedative effects of diphenhydramine than tests of "off road" driving. The implications are discussed.

Single and repeated dose comparison of three antihistamines and phenylpropanolamine: psychomotor performance and subjective appraisals of sleep

1 In a double-blind cross-over study, nine healthy male students received placebo, brompheniramine 12 mg), carbinoxamine (12 mg), clemastine (1 mg), and phenylpropanolamine (50 mg) orally. Three doses of each drug were given: at 08.30 h and 21.00 h on the first day of treatment and at 08.30 h on the following day. 2 Psychomotor skills and subjective feelings were recorded before and 2, 6 and 12 h after the first dose on day 1 as well as before and 2 and 6 h after the third dose on day 2. Subjective appraisals of sleep were requested on the morning of day 2. 3 All antihistamines tended to cause subjective drowsiness on the first day of treatment. Drowsiness was felt for a maximum of 2 h after carbinoxamine, 6 h after brompheniramine, and 12 h after clemastine. In contrast to antihistamines, phenylpropanolamine made subjects more alert and quick witted. Tolerance to the antihistamine-induced drowsiness developed on the second day. 4 Divided attention, tracking, speed anticipation and sleep were not affected by any drug. Carbinoxamine slowed reactions 2 h after the first dose, but no impairment was measured in objective tests after brompheniramine or clemastine. 5 Phenylpropanolamine improved reaction speed and reaction accuracy and enhanced flicker recognition throughout the study. Phenylpropanolamine plasma levels and improvement in flicker fusion test results correlated with each other on day 2. 6 The results suggest that phenylpropanolamine and the antihistamines studied are comparatively harmless to psychomotor performance and driving skills.

Azatadine maleate in perennial allergic rhinitis: effects on clinical symptoms and choice reaction time

1 The efficacy of the antihistamine azatadine maleate at maximum recommended dosage (4 mg/day) for 1 week was assessed relative to placebo in a double-blind crossover study of twenty patients with perennial allergic rhinitis. 2 Sixteen patients reported significant improvement in their clinical symptoms while taking the active drug. 3 The size of skin test weals for both histamine provocation and common inhalant allergens (prick test) diminished significantly after the azatadine treatment. There was no correlation between inhibition of skin reactions and symptom improvement. 4 Eight subjects reported sedative effects attributable to azatadine maleate. Their performance on a choice reaction to placebo occurred in the non-sedated group.

Effects of azatadine maleate on subjective appraisal and psychomotor functions relevant to driving performance

Studies were carried out in normal healthy male subjects to assess the effects on psychomotor functions and subjective ratings of performance after acute administration of azatadine maleate, a potent antihistamine with additional antiserotonin activity. In the first trial, 2 mg azatadine was compared with another new antihistamine Sch 12169 (2 mg) and placebo. In a second trial, higher doses of azatadine (4 mg and 8 mg) were compared with dexchlorpheniramine (4 mg) and placebo. Both trials were of a double-blind, randomized Latin square design and subjects were assessed using a battery of tests, after administration of each trial drug. The time and sequence of tests were standarized, with a 1-week interval between test sessions. The results showed that azatadine did not produce significant impairment of psychomotor function at either the standard 2 mg or the maximum recommended 4 mg per day dosage level. Permormance was only significantly impaired, compared with that after placebo, at the 8 mg dose level and was of a similar order to that observed after dexchlorpheniramine at the usual 4 mg dosage. It is suggested, therefore, that at the normal recommended dosage of 2 mg per day, azatadine is not likely to impair driving ability.

Clobazam, a 1,5-benzodiazepine, and car-driving ability

1 The effects of clobazam, a new anxiolytic agent (a 1,5-benzodiazepine) on car-driving ability and other tests of psychomotor performance were investigated in a double-blind, cross-over study v. placebo in normal volunteers. 2 Clobazam (20 mg) or placebo was given nightly for six nights to ten volunteers and subjective ratings of sleep and subjective and objective assessments of behaviour and psychomotor performance on the morning following drug ingestion were recorded. 3 Clobazam significantly improved the subjective ratings of sleep induction and quality of induced sleep. 4 Clobazam did not significantly impair performance in a variety of psychomotor tests and car-driving ability. 5 The validity of the measures used and the relevance of the findings to real life car-driving situations are discussed.