Effects of fexofenadine and hydroxyzine on brake reaction time during car-driving with cellular phone use

Why fexofenadine is considered as a truly non-sedating antihistamine with no brain penetration: a systematic review

OBJECTIVE

Fexofenadine is a second-generation inverse agonist of H1-receptor of histamine which is highly selective with proven efficacy in relieving symptoms associated with allergic conditions. It has an additional benefit of not penetrating the blood-brain barrier and therefore do not induce sedation and not impair the cognitive function/psychomotor performance. This review aimed at providing evidence based on available controlled studies to reinforce the non-sedative property of fexofenadine for treating patients with allergic rhinitis and urticaria.

METHODS

We performed an electronic literature search using keywords such as fexofenadine, drowsiness, somnolence, sedation, fatigue, cognitive, impairment, psychomotor, driving performances, sleep, rapid eye movement, alertness, clinical study, in vitro study, in vivo study, and pharmacodynamics in the Embase search engine. The review included randomized controlled trials, review articles, systematic reviews, and meta-analyses, together with post-marketing analysis conducted in healthy subjects and patients with allergy and were focused on comparing the antihistaminic potential or safety of fexofenadine with other antihistamines or placebo.

RESULTS

Positron emission tomography (PET) and proportional impairment ratio (PIR) data along with other objective tests from various studies confirmed the non-sedative property of fexofenadine. Results of brain H1-receptor occupancy (H1RO) obtained from PET showed no H1RO by fexofenadine, the receptor which is known to cause sedation of H1 antihistamines. Most studies calculating PIR value as 0 showed fexofenadine to be a non-impairing oral antihistamine regardless of dose. Clinical trials in adults and children showed fexofenadine to be well tolerated without sedative effect or impairment of cognitive/psychomotor function even at higher than recommended doses.

CONCLUSION

Published literature based on various parameters and clinical trials conducted for evaluating the effect of fexofenadine on sedation and central nervous system shows fexofenadine is both clinically effective and non-sedating.

Odevixibat: A Review of a Bioactive Compound for the Treatment of Pruritus Approved by the FDA

Odevixibat is synthesized through chemical modification of Benzothiazepine's structure. It is a tiny chemical that inhibits the ileal bile acid transporter and is used to treat a variety of cholestatic illnesses, including progressive familial intrahepatic cholestasis (PFIC). For cholestatic pruritus and liver disease development, bile acid transporter inhibition is a unique treatment strategy. Odevixibat reduces enteric bile acid reuptake. Oral odevixibat was also studied in children with cholestatic liver disease. Odevixibat received its first approval in the European Union (EU) in July 2021 for the treatment of PFIC in patients aged 6 months, followed by approval in the USA in August 2021 for the treatment of pruritus in PFIC patients aged 3 months. Bile acids in the distal ileum can be reabsorbed by the ileal sodium/bile acid cotransporter, a transport glycoprotein. Odevixibat is a sodium/bile acid co-transporter reversible inhibitor. An average 3 mg once-daily dose of odevixibat for a week resulted in a 56% reduction in the area under the curve of bile acid. A daily dose of 1.5 mg resulted in a 43% decrease in the area under the curve for bile acid. Odevixibat is also being evaluated in many countries for the treatment of other cholestatic illnesses, including Alagille syndrome and biliary atresia. This article reviews the updated information on odevixibat with respect to its clinical pharmacology, mechanism of action, pharmacokinetics, pharmacodynamics, metabolism, drug-drug interactions, pre-clinical studies, and clinical trials.

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.

Antihistamines for Allergic Rhinitis Treatment from the Viewpoint of Nonsedative Properties

Antihistamines targeting the histamine H₁ receptor play an important role in improving and maintaining the quality of life of patients with allergic rhinitis. For more effective and safer use of second-generation drugs, which are recommended by various guidelines, a classification based on their detailed characteristics is necessary. Antihistamines for first-line therapy should not have central depressant/sedative activities. Sedative properties (drowsiness and impaired performance) are associated with the inhibition of central histamine neurons. Brain H₁ receptor occupancy (H₁RO) is a useful index shown to be correlated with indices based on clinical findings. Antihistamines are classified into non-sedating (<20%), less-sedating (20–50%), and sedating (≥50%) groups based on H₁RO. Among the non-sedating group, fexofenadine and bilastine are classified into “non-brain-penetrating antihistamines” based on the H₁RO. These two drugs have many common chemical properties. However, bilastine has more potent binding affinity to the H₁ receptor, and its action tends to last longer. In well-controlled studies using objective indices, bilastine does not affect psychomotor or driving performance even at twice the usual dose (20 mg). Upon selecting antihistamines for allergic rhinitis, various situations should be taken into our consideration. This review summarizes that the non-brain-penetrating antihistamines should be chosen for the first-line therapy of mild allergic rhinitis.

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.

Road traffic crash risk associated with prescription of hydroxyzine and other sedating H1-antihistamines: A responsibility and case-crossover study

BACKGROUND

H1 antihistamines differ from each other by their ability to cross the blood-brain barrier. The resulting sedating effect can be sought in therapy but may be a driving hazard. The aim of this study was to estimate the impact of sedating H1-antihistamines on the risk of road traffic crash, with a particular focus on hydroxyzine which is also indicated as an anxiolytic in France.

METHODS

The study consisted in extracting and matching data from three French nationwide databases: the national healthcare insurance database, police reports and the police national database of injurious crashes. All sedating H1-antihistamines, including hydroxyzine, were considered in the study. A case-control analysis, in which responsible drivers were cases and non-responsible were controls was performed. A case-crossover analysis, comparing for the same subject exposure during a period immediately before the crash with exposure during an earlier period, was also conducted.

RESULTS

The extraction and matching procedures over the July 2005-December 2011 period led to the inclusion of 142,771 drivers involved in an injurious road traffic crash. The responsibility study found an increased risk of being responsible for an injurious road traffic crash in hydroxyzine users who were registered with a long-term chronic disease (mostly psychiatric disorders) on the day of the crash (OR=1.67 [1.22-2.30]). Among them, the risk was even higher in drivers with highest exposure levels (OR=2.60 [1.23-5.50]). There was no impact of sedating H1 antihistamine treatment initiation on the risk of crash.

CONCLUSION

Even if it is difficult to disentangle the part of the increased risk that would be causally related to hydroxyzine and the part related to behaviours of patients with a heavy psychiatric disorder, our study raises the alarm on the crash risk linked to hydroxyzine utilization in countries in which the anxiolytic indication is widespread.

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.

The effect of histidine on mental fatigue and cognitive performance in subjects with high fatigue and sleep disruption scores

Our previous study reported that a dried bonito broth known in Japan as 'dashi' improved or ameliorated mood states, including fatigue, during the daily lives of human subjects. Histidine is an amino acid that is present in dried bonito broth, and we sought to evaluate whether histidine would affect feelings of fatigue in humans. We investigated the effects of histidine intake on the feeling of fatigue, mood states and mental task performance by performing a placebo-controlled, double-blind crossover trial. Twenty subjects with high fatigue and sleep disruption scores were asked to ingest histidine or a placebo every day for two weeks. The subjects' mood states were evaluated using the Profile of Mood States (POMS) scale and a visual analog scale (VAS) for eight feelings (fatigue, depression, carelessness, drowsiness, clear thinking, motivation, attentiveness and concentration). We also measured subjects' cognitive performance using the CogHealth test battery. The fatigue T-scores on the POMS test decreased significantly following histidine ingestion compared to placebo ingestion (p<0.05). After two weeks of histidine ingestion, the reaction time for the working memory task in the CogHealth test battery was significantly shorten compared to placebo ingestion. The VAS scores for clear thinking and for attentiveness were increased significantly following histidine ingestion compared to placebo ingestion (p<0.05). These results suggest that daily ingestion of histidine may ameliorate feelings of fatigue, increase performance during working memory tasks, and improve the clear thinking and attentiveness.

Central nervous system effects of the second-generation antihistamines marketed in Japan--review of inter-drug differences using the proportional impairment ratio (PIR)-

Background

Second-generation antihistamines (AHs) have, in general, fewer sedative effects than the first-generation. However, important inter-drug differences remain in the degree of cognitive and/or psychomotor impairment. The extent to which a particular compound causes disruption can be conveniently compared, to all other AHs, using the Proportional Impairment Ratio (PIR). Although the PIR can differentiate the relative impairment caused by individual drugs, there is no indication of the reliability of the ratios obtained.

Objective

To calculate the PIRs –together with 95% confidence intervals (CIs), as an index of reliability– and compare AHs currently, or soon to be, available in Japan, with respect to their intrinsic capacity to cause impairment.

Methods

Results from studies of cetirizine, desloratadine, ebastine, fexofenadine, levocetirizine, loratadine, mequitazine, and olopatadine were included in the PIR calculations. All data utilised came from crossover studies in healthy volunteers which were randomised and placebo and positive-internal controlled. Existing databases from studies reporting the sedative effects of AHs on objective (speed, accuracy, memory) and subjective (feeling) psychometrics were augmented, via results from suitable studies published after the previous reviews. The null value for a PIR was one.

Results

A total of 45 studies were finally included for this review. Of the AHs assessed, fexofenadine, ebastine, and levocetirizine showed a PIR for objective tests of 0. However, only fexofenadine (PIR = 0.49) had an upper limit of the 95% CI of less than 1. Fexofenadine, levocetirizine, desloratadine, olopatadine, loratadine, and mequitazine all had a PIR for subjective ratings of 0, but the upper limits of the 95% CIs were all in excess of 1, although fexofenadine (PIR = 2.57) was the lowest.

Conclusions

The results show that there are differences between second-generation AHs in the extent of sedation produced. However, subjective ratings indicate that patients may not necessarily be aware of this.

Brain histamine H1 receptor occupancy measured by PET after oral administration of levocetirizine, a non-sedating antihistamine

OBJECTIVE

Histamine H1 receptor (H1R) antagonists often have sedative side effects, which are caused by the blockade of the neural transmission of the histaminergic neurons. We examined the brain H1R occupancy (H1RO) and the subjective sleepiness of levocetirizine, a new second-generation antihistamine, comparing fexofenadine, another non-sedating antihistamine, as a negative active control.

METHODS

Eight healthy volunteers underwent positron emission tomography (PET) imaging with [(11)C]doxepin, a PET tracer that specifically binds to H1Rs, after a single oral administration of levocetirizine (5 mg), fexofenadine (60 mg) or placebo in a double-blind crossover study. Binding potential ratios and H1ROs in the cerebral cortices regions were calculated using placebo. Subjective sleepiness was assessed with the Line Analogue Rating Scale and the Stanford Sleepiness Scale.

RESULTS

There was no significant difference between the mean brain H1RO after levocetirizine administration (8.1%; 95% CI: -9.8 to 26.0%) and fexofenadine administration (-8.0%; 95% CI: -26.7 to 10.6%). Similarly, subjective sleepiness was not significantly different between the two antihistamines and placebo. Neither subjective sleepiness nor plasma concentrations was significantly correlated with the brain H1RO of the two antihistamines.

CONCLUSION

At therapeutic dose, levocetirizine does not bind significantly to the brain H1Rs and does not induce significant sedation.

Medications and impaired driving

OBJECTIVE

To describe the association of specific medication classes with driving outcomes and provide clinical recommendations.

DATA SOURCES

The MEDLINE and EMBASE databases were searched for articles published from January 1973 to June 2013 on classes of medications associated with driving impairment. The search included outcome terms such as automobile driving, motor vehicle crash, driving simulator, and road tests.

STUDY SELECTION AND DATA EXTRACTION

Only English-language articles that contained findings from observational or interventional designs with ≥ 10 participants were included in this review. Cross-sectional studies, case series, and case reports were excluded.

DATA SYNTHESIS

Driving is an important task and activity for the majority of adults. Some commonly prescribed medications have been associated with driving impairment measured by road performance, driving simulation, and/or motor vehicle crashes. This review of 30 studies identified findings with barbiturates, benzodiazepines, hypnotics, antidepressants, opioid and nonsteroidal analgesics, anticonvulsants, antipsychotics, antiparkinsonian agents, skeletal muscle relaxants, antihistamines, anticholinergic medications, and hypoglycemic agents. Additional studies of medication impact on sedation, sleep latency, and psychomotor function, as well as the role of alcohol, are also discussed.

CONCLUSIONS

Psychotropic agents and those with central nervous system side effects were associated with measures of impaired driving performance. It is difficult to determine if such associations are actually a result of medication use or the medical diagnosis itself. Regardless, clinicians should be aware of the increased risk of impaired driving with specific classes of medications, educate their patients, and/or consider safer alternatives.

The role of P-glycoprotein in CNS antihistamine effects

RATIONALE

P-glycoprotein (P-gp) is a drug efflux pump expressed, amongst others, on the luminal surface of the cerebral endothelial cells forming the blood-brain barrier. Studies in rodents have demonstrated that antihistamines that are substrates of the P-gp transporter display no or minor central nervous system (CNS) effects as compared to antihistamines that are not P-gp transporter substrates.

OBJECTIVES

The present study explored whether P-gp contributes in similar ways to the occurrence of sedative effects of antihistamines in humans.

METHODS

An fMRI study was conducted according to a double-blind, randomized, placebo-controlled, cross-over design in 13 healthy volunteers. Participants received cetirizine 15 mg (an antihistamine), verapamil 120 mg (a P-gp blocker), a combination of cetirizine + verapamil, and a placebo. Brain activity was assessed while conducting the attention network test (ANT) in a 3T magnetic resonance scanner. The ANT measures three independent attention domains: i.e., alerting, orienting, and executive attention. It was expected that the combined treatment of cetirizine with verapamil would prevent efflux of cetirizine from the CNS, thus increasing attentional impairment, as compared to cetirizine administered alone.

RESULTS

The present study provides evidence that the P-gp transporter is involved in central antihistamine effects in humans. Participants were less alert during the combined treatment of cetirizine and verapamil as indicated by longer reaction times and decreased blood oxygen level-dependent response in the right superior temporal gyrus.

CONCLUSION

It is concluded that the affinity for the P-gp transporter may contribute to the lower incidence of CNS side effects of certain antihistamines.

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.

Carryover effect on next-day sleepiness and psychomotor performance of nighttime administered antihistaminic drugs: a randomized controlled trial

BACKGROUND

Antihistamines with strong sedative-hypnotic properties are frequently prescribed for insomnia secondary to allergy, but the potential risks of such administration have not been fully elucidated.

SUBJECTS AND METHODS

This randomized, double-blind, placebo-controlled crossover study was conducted to evaluate next-day sleepiness and psychomotor performance following the administration of antihistamines. Twenty-two healthy male participants participated in four drug administration sessions with more than a 1-week interval between the sessions. Either zolpidem 10 mg, or diphenhydramine 50 mg, or ketotifen 1 mg, or a placebo was administered before sleep, and polysomnography was conducted to evaluate sleep. In the morning and afternoon of the day after administration, the participants were evaluated for subjective sleepiness, objective sleepiness, and psychomotor performance.

RESULTS

The antihistamines with high blood-brain barrier-crossing efficiency were significantly associated with sleepiness and psychomotor performance decline the next day. Ketotifen showed the strongest carryover effect, followed by diphenhydramine. Compared with the placebo, no significant carryover effect was observed with zolpidem.

CONCLUSION

The results suggest that the risk-benefit balance should be considered in the ready use of antihistamines that easily cross the blood-brain barrier for alleviating secondary insomnia associated with allergies.

Predicting psychopharmacological drug effects on actual driving performance (SDLP) from psychometric tests measuring driving-related skills

RATIONALE

There are various methods to examine driving ability. Comparisons between these methods and their relationship with actual on-road driving is often not determined.

OBJECTIVE

The objective of this study was to determine whether laboratory tests measuring driving-related skills could adequately predict on-the-road driving performance during normal traffic.

METHODS

Ninety-six healthy volunteers performed a standardized on-the-road driving test. Subjects were instructed to drive with a constant speed and steady lateral position within the right traffic lane. Standard deviation of lateral position (SDLP), i.e., the weaving of the car, was determined. The subjects also performed a psychometric test battery including the DSST, Sternberg memory scanning test, a tracking test, and a divided attention test. Difference scores from placebo for parameters of the psychometric tests and SDLP were computed and correlated with each other. A stepwise linear regression analysis determined the predictive validity of the laboratory test battery to SDLP.

RESULTS

Stepwise regression analyses revealed that the combination of five parameters, hard tracking, tracking and reaction time of the divided attention test, and reaction time and percentage of errors of the Sternberg memory scanning test, together had a predictive validity of 33.4%.

CONCLUSION

The psychometric tests in this test battery showed insufficient predictive validity to replace the on-the-road driving test during normal traffic.

Short-term effects of morning versus evening dose of hydroxyzine 50 mg on cognition in healthy volunteers

It is well known that the sedative properties of antihistamines can differ considerably between individual drugs. Several factors have been suggested to determine the presence, absence, and/or magnitude of sedation by antihistamines. Research has suggested that the sedative effects caused by central H1 blockade partly depend on the availability of histamine competing for the same receptor and that this competition is affected by a mechanism related to sleep. Consequently, the present study was designed to compare the effects of evening and morning doses of the first-generation antihistamine hydroxyzine on cognition. It was expected that the sedative effect of hydroxyzine would be apparent in the evening after an evening dose but would be smaller in the morning after a morning dose owing to the greater release of histamine shortly after awakening. Eighteen participants (9 females) participated in a placebo-controlled, randomized, double-blind 3-way crossover design. Performance was assessed using several psychomotor tests: that is, divided attention task, critical tracking task, stop signal task, the attention network test, and the experimental attention switch task. Results demonstrated that evening doses of hydroxyzine impaired performance on the divided attention and the attention network test. Impairment after morning doses was generally larger in magnitude and affected performance measures in all tasks. It is concluded that hydroxyzine-induced impairment at tmax is more prominent after morning doses compared with evening doses and that the present study could not present direct evidence to substantiate the hypothesis that histamine availability inversely affects the magnitude of antihistamine impairment.

Brain histamine H1 receptor occupancy of loratadine measured by positron emission topography: comparison of H1 receptor occupancy and proportional impairment ratio

AIMS

We have evaluated the sedative properties of H1-antihistamines by using positron emission tomography (PET) and ¹¹C-doxepin. The purpose of the present study was to measure histamine H1 receptor occupancy (H1RO) of loratadine 10 mg in patients with allergic rhinitis and to compare this occupancy with that of d-chlorpheniramine 2 mg, a first-generation antihistamine. We also compared our PET findings with the proportional impairment ratio reported by McDonald et al.

METHODS

The H1RO of loratadine 10 mg and d-chlorpheniramine 2 mg were evaluated in human brains in a double-blind and crossover design using ¹¹C-doxepin PET. Eleven young male patients with allergic rhinitis were examined by PET following oral single administration of loratadine 10 mg and d-chlorpheniramine 2 mg.

RESULTS

Loratadine 10 mg occupied 11.7 ± 19.5% of histamine H1 receptors in the cortex, whereas d-chlorpheniramine 2 mg occupied 53.0 ± 33.2% in the same area, suggesting a non-sedating property of loratadine at a dose of 10 mg. The H1RO values of loratadine and d-chlorpheniramine as well as those of previous studies were found to be significantly proportional to the proportional impairment ratio (r = 0.899).

CONCLUSION

Measurement of H1RO is a sensitive and absolute method to characterize the non-sedating property of drugs with H1 antagonistic activity.

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 sedative and nonsedative antihistamines on prefrontal activity during verbal fluency task in young children: a near-infrared spectroscopy (NIRS) study

INTRODUCTION

Antagonists of histamine H(1) receptors (antihistamines) are widely used for the treatment of allergic disorders in children. These drugs' sedative effect on brain function, however, has been mostly examined in adults.

OBJECTIVE

The objective of this study was to examine the effects of anitihistamines on prefrontal cortex activity in young children using near-infrared spectroscopy (NIRS), a novel brain-imaging method.

MATERIALS AND METHODS

In 15 healthy children (mean age, 7.7 years), we examined changes of oxygenated hemoglobin concentration in the prefrontal cortex while they performed a verbal fluency task 3 h after taking a sedating antihistamine (ketotifen), nonsedating antihistamine (epinastine), or placebo.

RESULTS

Ketotifen significantly impaired behavioral performance and cortical activation at the lateral prefrontal cortex compared with placebo. There were no sedative effects on neural response or behavioral performance after epinastine administration.

CONCLUSIONS

NIRS revealed that sedating and nonsedating antihistamines exert differential effects on brain hemodynamic response in young children.

Suppression of histamine- and allergen-induced skin reactions: comparison of first- and second-generation antihistamines

BACKGROUND

Nonsedating antihistamines (nsAHs) are recommended as first-line therapeutics for the treatment of mast cell-driven disorders, including allergic rhinitis and urticaria. However, their superiority over first-generation AHs (fgAHs) has recently been called into question, mainly because of the lack of supporting head-to-head therapeutic studies.

OBJECTIVE

To compare the effects of 3 modem nsAHs with those of the fgAH hydroxyzine on histamine- and allergen-induced skin reactions in a controlled, double-blind, clinical trial.

METHODS

Skin prick tests with histamine and Dermatophagoides pteronyssinus extract were performed before and 4 hours after treatment with hydroxyzine, 25 mg; desloratadine, 5 mg; epinastine, 20 mg; fexofenadine, 120 mg; or placebo. Wheal and erythema development was evaluated by digital photography and planimetric analyses.

RESULTS

The nsAHs prevented the development of positive reactions to histamine in only 10% to 20% of all individuals tested (n = 75). In contrast, more than 50% of all hydroxyzine-treated individuals showed negative test reactions to histamine (ie, wheals <7 mm2 in area or <3 mm in diameter). Similar differences, although less pronounced, were detected when comparing the effects of nsAHs with hydroxyzine on D pteronyssinus prick testing in a limited number of D pteronyssinus-sensitized individuals.

CONCLUSIONS

These results indicate that hydroxyzine is more effective than nsAHs when given as recommended in suppressing histamine-induced or allergic skin reactions. Our results suggest that higher doses of nsAHs than those currently recommended are required for the treatment of skin responses to obtain antihistaminic and antiallergic effects that are equivalent to those of fgAHs.

Sedation and antihistamines: an update. Review of inter-drug differences using proportional impairment ratios

BACKGROUND

The use of antihistamines (AHs) has been associated with cognitive and psychomotor impairments, largely caused by the sedative properties of many of these drugs. Due to the ambulant nature of the population using AHs, it is important to evaluate these effects using standardised methodology and psychometric tests. A previous extensive review of the literature collated the results of studies of H(1) receptor antagonists to determine the extent to which a particular AH produced impairments on a battery of psychometric tests by calculating a proportional impairment ratio for each AH.

OBJECTIVE

In light of a number of major studies published following the previous review, and the development of the second and new-generation AHs, the present review aims to add to the database and update the review, using the same methodology.

RESULTS AND CONCLUSION

The newer generation AHs appear to be the least impairing, and the first generation, as expected, appear to be the most impairing. There are also differences within the AH drug generations. The review highlights the necessity to consider the sedating potential of AHs, along with other factors such as efficacy, when prescribing AHs to ambulant patients.

Fexofenadine hydrochloride in the treatment of allergic disease: a review

Fexofenadine is a selective, non-sedating H1 receptor antagonist, marketed in the United States since 2000. The FDA approved an oral suspension in 2006, for the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria in children. The tablet, capsule, and oral suspension are bioequivalent. Although fexofenadine does not use P450 CYP 3A4 it does interact with a number of drugs at P-glycoprotein and organic anion transporter polypeptides. The risk of toxicity from other drugs may increase with the administration of fexofenadine. Orange and grapefruit juices reduce the bioavailability of fexofenadine. Fexofenadine has been shown to have an impact on inflammatory mediators, other than histamine, such as decreasing the production of LTC₄, LTD₄, LTE₄, PGE₂, and PGF_2α; inhibiting cyclo-oxygenase 2, thromboxane; limiting iNOS generation of NO; decreasing cytokine levels (ICAM-1, ELAM-1, VCAM-1, RANTES, I-TAC, MDC, TARC, MMP-2, MMP-9, tryptase); and diminishing eosinophil adherence, chemotaxis, and opsonization of particles. These effects may provide benefit to some of the inflammatory responses of an acute allergic reaction and provide a basis for future development of H1 antagonists with stronger anti-inflammatory effects. These studies also support the contention that fexofenadine is effective for the treatment of allergic rhinits and chronic idiopathic urticaria.

Next-day cognition, psychomotor function, and driving-related skills following nighttime administration of eszopiclone

OBJECTIVE

To evaluate next-day driving ability, as assessed by brake reaction time (BRT), and cognitive/psychomotor function following nighttime administration of 3 mg eszopiclone.

METHODS

Two randomized, double-blind, placebo-controlled, cross-over studies were performed in healthy volunteers (n = 32) and patients with primary insomnia (n = 32). Study participants received nighttime dosing of 3 mg eszopiclone or placebo. BRT and a psychometric test battery were used to assess the next-day effects of eszopiclone treatment.

RESULTS

In both studies, driving ability and measures of cognitive and psychomotor function were not impaired the morning after eszopiclone, as compared to placebo. All eszopiclone subjects reported improved ease in getting to sleep and quality of sleep with no significant changes in behavior upon awakening. A significant increase in next-day feelings of sedation was reported in healthy volunteers, but not in patients with primary insomnia, following eszopiclone treatment relative to placebo. Sleep induction, maintenance, duration, and efficiency, as assessed by PSG, were significantly improved following eszopiclone treatment in patients with insomnia.

CONCLUSIONS

Nighttime administration of 3 mg eszopiclone improved objective and subjective sleep measures in patients with insomnia (and subjective sleep measures in healthy patients) and did not impair next-day driving-related skills or measures of cognition in either study population relative to placebo.

Brain histamine H1 receptor occupancy of orally administered antihistamines, bepotastine and diphenhydramine, measured by PET with 11C-doxepin

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

'Bepotastine besilate' is a novel second-generation antihistamine developed in Japan and its antiallergic effects have already been demonstrated by various studies. However, only a few clinical studies regarding its sedative property are available. In addition, histamine H(1) receptor occupancy (H(1)RO) of this new antihistamine has never been measured by positron emission tomography (PET).

WHAT THIS STUDY ADDS

This paper provides the first measurement result of cerebral H(1)RO of bepotastine besilate (approximately 15%) as determined by PET. This result is in accordance with the clinical classification of bepotastine as a second-generation antihistamine. In addition, the relationship between subjective sleepiness and cerebral H(1)RO of this second-generation antihistamine is demonstrated for the first time using a placebo-controlled crossover study design. AIMS Antihistamines are frequently used for treating various allergic diseases, but often induce sedation. The degree of sedation can be evaluated by measuring histamine H(1) receptor occupancy (H(1)RO) in the brain using positron emission tomography (PET). The aim was to measure H(1)RO of bepotastine, a new second-generation antihistamine, and to compare it with that of diphenhydramine.

METHODS

Eight healthy male volunteers (mean age +/- SD 24.4 +/- 3.3 years) were studied after single oral administration of bepotastine (10 mg), diphenhydramine (30 mg) or placebo, by PET imaging with (11)C-doxepin in a crossover study design. Binding potential ratio and H(1)ROs were calculated using placebo data and were compared between bepotastine and diphenhydramine in the anterior and posterior cingulate gyri (ACG and PCG, respectively), superior and inferior frontal cortices (SFC and IFC, respectively), orbitofrontal cortex (OFC), insular cortex (IC), lateral and medial temporal cortices (LTC and MTC, respectively), parietal cortex (PC), occipital cortex (OC) and sensorimotor cortex (SMC). Plasma concentration of each antihistamine was measured, and its correlation to H(1)RO was examined.

RESULTS

H(1)RO after bepotastine treatment was significantly lower than that after diphenhydramine treatment in all cortical regions (P < 0.001). Mean H(1)ROs of bepotastine and diphenhydramine were 14.7% and 56.4%, respectively. H(1)ROs of both bepotastine and diphenhydramine correlated to their respective drug plasma concentration (P < 0.001).

CONCLUSION

Oral bepotastine (10 mg), with its relatively low H(1)RO and thus minimal sedation, has the potential for use as a mildly or slightly sedative antihistamine in the treatment of various allergic disorders.

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.

Visual and cognitive predictors of performance on brake reaction test: Salisbury eye evaluation driving study

OBJECTIVES

Concern for driving safety has prompted research into understanding factors related to performance. Brake reaction speed (BRS), the speed with which persons react to a sudden change in driving conditions, is a measure of performance. Our aim is to determine the visual, cognitive, and physical factors predicting BRS in a population sample of 1425 older drivers.

METHODS

The Maryland Department of Motor Vehicles roster of persons aged 67-87 and residing in Salisbury, MD, was used for recruitment of the study population. Procedures included the following: habitual, binocular visual acuity using ETDRS charts, contrast sensitivity using a Pelli-Robson chart, visual fields assessed with a 81-point screening Humphrey field at a single intensity threshold, and a questionnaire to ascertain medical conditions. Cognitive status was assessed using a standard battery of tests for attention, memory, visuo-spatial, and scanning. BRS was assessed using a computer-driven device that measured separately the initial reaction speed (IRS) (from light change to red until removing foot from accelerator) and physical response speed (PRS) (removing foot from accelerator to full brake depression). Five trial times were averaged, and time was converted to speed.

RESULTS

The median brake reaction time varied from 384 to 5688 milliseconds. Age, gender, and cognition predicted total BRS, a non-informative result as there are two distinct parts to the task. Once separated, decrease in IRS was associated with low scores on cognitive factors and missing points on the visual field. A decrease in PRS was associated with having three or more physical complaints related to legs and feet, and poorer vision search. Vision was not related to PRS.

CONCLUSION

We have demonstrated the importance of segregating the speeds for the two tasks involved in brake reaction. Only the IRS depends on vision. Persons in good physical condition may perform poorly on brake reaction tests if their vision or cognition is compromised.

Functional brain mapping of actual car-driving using [18F]FDG-PET

AIMS

This study aims at identifying the brain activation during actual car-driving on the road, and at comparing the results to those of previous studies on simulated car-driving.

METHODS

Thirty normal volunteers, aged 20 to 56 years, were divided into three subgroups, active driving, passive driving and control groups, for examination by positron emission tomography (PET) and [18F]2-deoxy-2-fluoro-D-glucose (FDG). The active driving subjects (n = 10) drove for 30 minutes on quiet normal roads with a few traffic signals. The passive driving subjects (n = 10) participated as passengers on the front seat. The control subjects (n = 10) remained seated in a lit room with their eyes open. Voxel-based t-statistics were applied using SPM2 to search brain activation among the subgroups mentioned above.

RESULTS

Significant brain activation was detected during active driving in the primary and secondary visual cortices, primary sensorimotor areas, premotor area, parietal association area, cingulate gyrus, the parahippocampal gyrus as well as in thalamus and cerebellum. The passive driving manifested a similar-looking activation pattern, lacking activations in the premotor area, cingulate and parahippocampal gyri and thalamus. Direct comparison of the active and passive driving conditions revealed activation in the cerebellum.

CONCLUSION

The result of actual driving looked similar to that of simulated driving, suggesting that visual perception and visuomotor coordination were the main brain functions while driving. In terms of attention and autonomic arousal, however, it seems there was a significant difference between simulated and actual driving possibly due to risk of accidents. Autonomic and emotional aspects of driving should be studied using an actual driving study-design.

The physiological and pathophysiological roles of neuronal histamine: an insight from human positron emission tomography studies

Histamine neurons are exclusively located in the posterior hypothalamus, and project their fibers to almost all regions of the human brain. Although a significant amount of research has been done to clarify the functions of the histaminergic neuron system in animals, a few studies have been reported on the roles of this system in the human brain. In past studies, we have been able to clarify some of the functions of histamine neurons using different methods, such as histamine-related gene knockout mice or human positron emission tomography (PET). The histaminergic neuron system is known to modulate wakefulness, the sleep-wake cycle, appetite control, learning, memory and emotion. Accordingly we have proposed that histamine neurons have a dual effect on the CNS, with both stimulatory and suppressive actions. As a stimulator, neuronal histamine is one of the most important systems that stimulate and maintain wakefulness. Brain histamine also functions as a suppressor in bioprotection against various noxious and unfavorable stimuli of convulsion, drug sensitization, denervation supersensitivity, ischemic lesions and stress susceptibility. This review summarizes our works on the functions of histamine neurons using human PET studies, including the development of radiolabeled tracers for histamine H1 receptors (H1R: (11)C-doxepin and (11)C-pyrilamine), PET measurements of H1R in depression, schizophrenia, and Alzheimer's disease (AD), and studies on the sedative effects of antihistamines using H(2)(15)O and H1R occupancy in the human brain. These molecular and functional PET studies in humans are useful for drug development in this millennium.

Efficacy and central nervous system impairment of newer-generation prescription antihistamines in seasonal allergic rhinitis

Allergic rhinitis is a highly prevalent disorder and oral antihistamines are often used to manage patient symptoms. Older-generation antihistamines, such as diphenhydramine and chlorpheniramine, are effective at relieving the symptoms of seasonal allergic rhinitis (SAR); however, they are associated with adverse events, including sedation and impairment, at, or above, the recommended dose. Newer-generation antihistamines, such as desloratadine, cetirizine and fexofenadine, were developed to minimize adverse events. In this article, studies examining newer-generation antihistamines in adults and children were reviewed. The clinical evidence confirms that desloratadine, cetirizine and fexofenadine are effective at managing the symptoms of SAR in adults and children; however, cetirizine is more likely to cause sedation. Physician intervention is paramount to SAR symptom management. It is essential that appropriate treatment relieves SAR symptoms with absent or minimal adverse events. This is particularly important for those patients involved in skilled and cognitive activities or safety-critical jobs.