Stimulating effects of the antihistamine fexofenadine: testing the dopamine transporter hypothesis

A systematic review of amnestic and non-amnestic mild cognitive impairment induced by anticholinergic, antihistamine, GABAergic and opioid drugs

BACKGROUND

Mild cognitive deficits are experienced by 18% of community-dwelling older adults, many of whom do not progress to dementia. The effect of commonly used medication on subtle impairments in cognitive function may be under-recognized.

OBJECTIVE

The aim of the review was to examine the evidence attributing amnestic or non-amnestic cognitive impairment to the use of medication with anticholinergic, antihistamine, GABAergic or opioid effects.

METHODS

MEDLINE and EMBASE were searched for randomized, double-blind, placebo-controlled trials of adults without underlying central nervous system disorders who underwent detailed neuropsychological testing prior to and after oral administration of drugs affecting cholinergic, histaminergic, GABAergic or opioid receptor pathways. Seventy-eight studies were identified, reporting 162 trials testing medication from the four targeted drug classes. Two investigators independently appraised study quality and extracted relevant data on the occurrence of amnestic, non-amnestic or combined cognitive deficits induced by each drug class. Only trials using validated neuropsychological tests were included. Quality of the evidence for each drug class was assessed based on consistency of results across trials and the presence of a dose-response gradient.

RESULTS

In studies of short-, intermediate- and long-acting benzodiazepine drugs (n = 68 trials), these drugs consistently induced both amnestic and non-amnestic cognitive impairments, with evidence of a dose-response relationship. H(1)-antihistamine agents (n = 12) and tricyclic antidepressants (n = 15) induced non-amnestic deficits in attention and information processing. Non-benzodiazepine derivatives (n = 29) also produced combined deficits, but less consistently than benzodiazepine drugs. The evidence was inconclusive for the type of cognitive impairment induced by different bladder relaxant antimuscarinics (n = 9) as well as for narcotic agents (n = 5) and antipsychotics (n = 5). Among healthy volunteers >60 years of age, low doses of commonly used medications such as lorazepam 0.5 mg, oxybutynin immediate release 5 mg and oxycodone 10 mg produced combined deficits.

CONCLUSION

Non-amnestic mild cognitive deficits are consistently induced by first-generation antihistamines and tricyclic antidepressants, while benzodiazepines provoke combined amnestic and non-amnestic impairments. Risk-benefit considerations should be discussed with patients in order to enable an informed choice about drug discontinuation or substitution to potentially reverse cognitive adverse effects.

Acute and subchronic effects of bilastine (20 and 40 mg) and hydroxyzine (50 mg) on actual driving performance in healthy volunteers

Bilastine is a new second-generation H1 antagonist. Although bilastine has been demonstrated to produce little or no performance impairment in laboratory tests, it cannot be excluded that it produces impairments in real-life performance such as driving. This study aims to assess the effects of two doses of bilastine (20 and 40 mg) on actual driving after single and repeated administration. Hydroxyzine 50 mg was included as an active control. Twenty-two participants (11 females, 11 males) were tested in a placebo-controlled, randomized, double-blind, four-way cross-over design. Participants were treated with once-daily doses for eight consecutive days. On day 1 and 8 of each treatment period participants performed an actual highway driving test. The primary variable was standard deviation of lateral position (SDLP), a measure of weaving. Results demonstrated that hydroxyzine significantly increased SDLP on days 1 and 8 of treatment. Bilastine did not affect SDLP. It is concluded that hydroxyzine produces severe driving impairment after single doses and that this impairment only partly mitigates over time due to a lack of complete tolerance. Bilastine did not produce any driving impairment after single and repeated doses and can be safely used in traffic in doses up to 40 mg.

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.

Histamine H1 receptor antagonist cetirizine impairs working memory processing speed, but not episodic memory

BACKGROUND AND PURPOSE

The histaminergic neurotransmitter system is currently under investigation as a target for drug treatment of cognitive deficits in clinical disorders. The therapeutic potential of new drugs may initially be screened using a model of histaminergic dysfunction, for example, as associated with the use of centrally active antihistamines. Of the selective second generation antihistamines, cetirizine has been found to have central nervous system effects. The aim of the present study was to determine whether cetirizine can be used as a tool to model cognitive deficits associated with histaminergic hypofunction.

EXPERIMENTAL APPROACH

The study was conducted according to a three-way, double-blind, cross-over design. Treatments were single oral doses of cetirizine 10 and 20 mg and placebo. Effects on cognition were assessed using tests of word learning, memory scanning, vigilance, divided attention, tracking and visual information processing speed.

KEY RESULTS

Cetirizine 10 mg impaired tracking performance and both doses impaired memory scanning speed. None of the other measures indicated impaired performance.

CONCLUSION AND IMPLICATIONS

Cetirizine affects information processing speed, but these effects were not sufficient to serve as a model for cognitive deficits in clinical disorders.

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.

Comparing the stimulant effects of the H1-antagonist fexofenadine with 2 psychostimulants, modafinil and methylphenidate

BACKGROUND

Although antihistamines are known for their sedative adverse effects, fexofenadine was previously shown to have stimulating effects. These stimulant effects were rather mild in magnitude and were only demonstrated in tasks with a high workload.

AIM

The present study was set up to compare the magnitude of the stimulant effect of fexofenadine with those of 2 psychostimulants, modafinil and methylphenidate.

METHOD

Sixteen healthy volunteers (5 males and 11 females; mean age, 21.8 years) participated in a 4-way, placebo-controlled, crossover study. The effects of fexofenadine (360 mg), modafinil (200 mg), methylphenidate (20 mg), and placebo were compared in a critical tracking, divided attention, motor impulsivity, and vigilance task.

RESULTS

In this study, no significant stimulant effects of fexofenadine were found in any of the tasks. Modafinil only improved reaction time in the vigilance task, whereas methylphenidate improved performance in the divided attention and vigilance tasks. In addition, performance after methylphenidate treatment was also better than after fexofenadine in the divided attention and vigilance tasks.

CONCLUSION

From the results, it can be concluded that the stimulating effects of methylphenidate are confirmed, whereas the stimulating effects of fexofenadine were not demonstrated in this study. It is evident that the stimulating effects of fexofenadine, which were apparent in previous studies, are not of the same magnitude as the effects of known psychostimulants such as methylphenidate.

Effects of L-histidine depletion and L-tyrosine/L-phenylalanine depletion on sensory and motor processes in healthy volunteers

BACKGROUND AND PURPOSE

Animal studies show that histamine plays a role in cognitive functioning and that histamine H3-receptor antagonists, which increase histaminergic function through presynaptic receptors, improve cognitive performance in models of clinical cognitive deficits. In order to test such new drugs in humans, a model for cognitive impairments induced by low histaminergic functions would be useful. Studies with histamine H1-receptor antagonists have shown limitations as a model. Here we evaluated whether depletion of L-histidine, the precursor of histamine, was effective in altering measures associated with histamine in humans and the behavioural and electrophysiological (event-related-potentials) effects.

EXPERIMENTAL APPROACH

Seventeen healthy volunteers completed a three-way, double-blind, crossover study with L-histidine depletion, L-tyrosine/L-phenylalanine depletion (active control) and placebo as treatments. Interactions with task manipulations in a choice reaction time task were studied. Task demands were increased using visual stimulus degradation and increased response complexity. In addition, subjective and objective measures of sedation and critical tracking task performance were assessed.

KEY RESULTS

Measures of sedation and critical tracking task performance were not affected by treatment. L-histidine depletion was effective and enlarged the effect of response complexity as measured with the response-locked lateralized readiness potential onset latency.

CONCLUSIONS AND IMPLICATIONS

L-histidine depletion affected response- but not stimulus-related processes, in contrast to the effects of H1-receptor antagonists which were previously found to affect primarily stimulus-related processes. L-histidine depletion is promising as a model for histamine-based cognitive impairment. However, these effects need to be confirmed by further studies.

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.