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

Applications of brain imaging methods in driving behaviour research

Applications of neuroimaging methods have substantially contributed to the scientific understanding of human factors during driving by providing a deeper insight into the neuro-cognitive aspects of driver brain. This has been achieved by conducting simulated (and occasionally, field) driving experiments while collecting driver brain signals of various types. Here, this sector of studies is comprehensively reviewed at both macro and micro scales. At the macro scale, bibliometric aspects of these studies are analysed. At the micro scale, different themes of neuroimaging driving behaviour research are identified and the findings within each theme are synthesised. The surveyed literature has reported on applications of four major brain imaging methods. These include Functional Magnetic Resonance Imaging (fMRI), Electroencephalography (EEG), Functional Near-Infrared Spectroscopy (fNIRS) and Magnetoencephalography (MEG), with the first two being the most common methods in this domain. While collecting driver fMRI signal has been particularly instrumental in studying neural correlates of intoxicated driving (e.g. alcohol or cannabis) or distracted driving, the EEG method has been predominantly utilised in relation to the efforts aiming at development of automatic fatigue/drowsiness detection systems, a topic to which the literature on neuro-ergonomics of driving particularly has shown a spike of interest within the last few years. The survey also reveals that topics such as driver brain activity in semi-automated settings or neural activity of drivers with brain injuries or chronic neurological conditions have by contrast been investigated to a very limited extent. Potential topics in driving behaviour research are identified that could benefit from the adoption of neuroimaging methods in future studies. In terms of practicality, while fMRI and MEG experiments have proven rather invasive and technologically challenging for adoption in driving behaviour research, EEG and fNIRS applications have been more diverse. They have even been tested beyond simulated driving settings, in field driving experiments. Advantages and limitations of each of these four neuroimaging methods in the context of driving behaviour experiments are outlined in the paper.

Do pharmacists counsel customers about the effects of sedating antihistamines on driving skills? A survey of community pharmacies in Saudi Arabia

Objective

To investigate the level of counselling regarding the effects of sedating antihistamines on driving skills provided by private community pharmacies in Madinah, Saudi Arabia.

Methods

This study randomly selected private community pharmacies. Mystery shoppers following a similar scenario individually visited these pharmacies. These clients asked for a commonly used brand of sedating antihistamine and noted the counselling offered by the pharmacist. If spontaneous counselling was not offered, necessary information regarding the medication’s use was requested. Finally, the content of counselling was documented.

Results

Of the 100 pharmacies selected, 12 were excluded for various reasons and 88 pharmacies were included in the study. Only 23 pharmacies offered spontaneous counselling. Although 73.9% of pharmacists (65 of 88), spontaneously or upon request, mentioned sedation as a side-effect, only one pharmacist warned the client against driving after taking the medication, and three other pharmacists warned against dealing with hazardous machinery. Other side-effects were almost ignored.

Conclusion

A life-threatening insufficiency in the quality of counselling at Saudi Arabian private community pharmacies exists. Traffic accidents, secondary to the side-effects of sedating antihistamines, may be avoided if proper counselling is offered. Saudi Arabian authorities should take appropriate actions to ensure optimal practice in community pharmacies.

Effects of levocetirizine and diphenhydramine on regional glucose metabolic changes and hemodynamic responses in the human prefrontal cortex during cognitive tasks

OBJECTIVE

Antihistamines often have sedative side effects. This was the first study to measure regional cerebral glucose (energy) consumption and hemodynamic responses in young adults during cognitive tests after antihistamine administration.

METHODS

In this double-blind, placebo-controlled, three-way crossover study, 18 healthy young Japanese men received single doses of levocetirizine 5 mg and diphenhydramine 50 mg at intervals of at least six days. Subjective feeling, task performances, and brain activity were evaluated during three cognitive tests (word fluency, two-back, and Stroop). Regional cerebral glucose consumption changes were measured using positron emission tomography with [¹⁸ F]fluorodeoxyglucose. Regional hemodynamic responses were measured using near-infrared spectroscopy.

RESULTS

Energy consumption in prefrontal regions was significantly increased after antihistamine administration, especially diphenhydramine, whereas prefrontal hemodynamic responses, evaluated with oxygenated hemoglobin levels, were significantly lower with diphenhydramine treatment. Stroop test accuracy was significantly impaired by diphenhydramine, but not by levocetirizine. There was no significant difference in subjective sleepiness.

CONCLUSIONS

Physiological "coupling" between metabolism and perfusion in the healthy human brain may not be maintained under pharmacological influence due to antihistamines. This uncoupling may be caused by a combination of increased energy demands in the prefrontal regions and suppression of vascular permeability in brain capillaries after antihistamine treatment. Further research is needed to validate this hypothesis.

A simulated car-driving study on the effects of acute administration of levocetirizine, fexofenadine, and diphenhydramine in healthy Japanese volunteers

OBJECTIVE

Antihistamines are often used for treating allergic rhinitis. However, many older antihistamines cause sedative side effects. The sedative effects of antihistamines on car-driving have been investigated. This has not been investigated for levocetirizine, a new-generation antihistamine, in Asian populations, and so we evaluated its sedative effects in healthy Japanese subjects.

METHODS

In this double-blind, placebo-controlled, four-way crossover study, healthy volunteers received single doses of levocetirizine 5 mg, fexofenadine 60 mg, diphenhydramine 50 mg, and placebo at intervals of at least 6 days. Simple brake reaction time and choice brake reaction time task (CBRT), a lateral tracking (LT) task, and a multiple task, a mixture of CBRT and LT task, were used to compare driving performance between the four drugs. Subjective sedation was also assessed.

RESULTS

The simple brake reaction time and CBRT, and the CBRT component of the multiple task, did not show any significant differences between the drugs. In contrast, the LT, both as a single parameter and as a component of the multiple task, showed significant differences between diphenhydramine and the newer-generation antihistamines in a manner that corresponds with subjective sedation.

CONCLUSIONS

Levocetirizine and fexofenadine did not impair psychomotor performance in subjects performing simulated car-driving tasks, while diphenhydramine did impair psychomotor performance in the subjects. Copyright © 2016 John Wiley & Sons, Ltd.

Large-scale functional brain network changes in taxi drivers: evidence from resting-state fMRI

Driving a car in the environment is a complex behavior that involves cognitive processing of visual information to generate the proper motor outputs and action controls. Previous neuroimaging studies have used virtual simulation to identify the brain areas that are associated with various driving-related tasks. Few studies, however, have focused on the specific patterns of functional organization in the driver's brain. The aim of this study was to assess differences in the resting-state networks (RSNs) of the brains of drivers and nondrivers. Forty healthy subjects (20 licensed taxi drivers, 20 nondrivers) underwent an 8-min resting-state functional MRI acquisition. Using independent component analysis, three sensory (primary and extrastriate visual, sensorimotor) RSNs and four cognitive (anterior and posterior default mode, left and right frontoparietal) RSNs were retrieved from the data. We then examined the group differences in the intrinsic brain activity of each RSN and in the functional network connectivity (FNC) between the RSNs. We found that the drivers had reduced intrinsic brain activity in the visual RSNs and reduced FNC between the sensory RSNs compared with the nondrivers. The major finding of this study, however, was that the FNC between the cognitive and sensory RSNs became more positively or less negatively correlated in the drivers relative to that in the nondrivers. Notably, the strength of the FNC between the left frontoparietal and primary visual RSNs was positively correlated with the number of taxi-driving years. Our findings may provide new insight into how the brain supports driving behavior.

The effect of a first-generation H1-antihistamine on postural control: a preliminary study in healthy volunteers

First-generation H1-antihistamines are known to cause fatigue and drowsiness, due to their poor receptor selectivity and their high penetration rate of the blood-brain barrier. However, little is known about the effects of first-generation H1-antihistamines on postural stability. The purpose of this study was to evaluate the effects of d-chlorpheniramine on postural stability using posturography with and without foam rubber. A double-blind study with three parallel groups was conducted. Twenty-seven healthy young volunteers (mean age 21.9 years) were recruited and orally administered d-chlorpheniramine, 2 or 4 mg, or placebo. Postural sway was measured every hour up to 8 h after administration. Two-legged stance tasks were performed by each subject in four conditions: eyes open or eyes closed and with or without foam rubber. Inter-group comparisons showed that the group receiving 4-mg d-chlorpheniramine showed significantly larger sway in the eyes open with foam rubber condition (visual and vestibular information available, somatosensory information reduced). Inter-subject analysis in the 4-mg d-chlorpheniramine group showed that the effect of d-chlorpheniramine on postural control was variable. Our results suggest that among the three main sensory systems responsible for postural control (visual, vestibular, and somatosensory), d-chlorpheniramine may have a larger effect on the visual and/or vestibular systems in susceptible individuals.

Caffeine counteracts impairments in task-oriented psychomotor performance induced by chlorpheniramine: a double-blind placebo-controlled crossover study

This study aimed to evaluate the effects of chlorpheniramine on psychomotor performance and the counteracting effects of caffeine on those sedative antihistamine actions. Sixteen healthy young men participated in this study. Using a double-blind placebo-controlled crossover design, each subject was administered one of the following conditions in a random order with a one-week interval: 'placebo-placebo', '4 mg of chlorpheniramine-placebo', 'placebo-200 mg of caffeine' or '4 mg of chlorpheniramine-200 mg of caffeine'. Before and after the treatments, psychomotor functions were assessed using a battery of tests. Additionally, subjective responses were assessed using a visual analogue scale (VAS). Psychomotor performance changed over time in different ways according to the combination of study medications. In the 'chlorpheniramine-placebo' condition, reaction times of the compensatory tracking task were significantly impaired compared with the other three conditions. In addition, the number of omission errors of the continuous performance test were significantly greater compared with the 'placebo-caffeine' condition. However, the response pattern of the 'chlorpheniramine-caffeine' condition was not significantly different from that of the 'placebo-placebo' condition. Changes of VAS for sleepiness were significantly greater in the 'chlorpheniramine-placebo' condition compared with the other three conditions. In conclusion, chlorpheniramine significantly increases subjective sleepiness and objectively impairs psychomotor performance. However, caffeine counteracts these sedative effects and psychomotor impairments.

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.