Sedation with "non-sedating" antihistamines: four prescription-event monitoring studies in general practice

Prevalence and Risk Factors of Inappropriate Drug Dosing among Older Adults with Dementia or Cognitive Impairment and Renal Impairment: A Systematic Review

Background: Potentially inappropriate medication prescribing is prevalent and well studied in older adults. However, limited data are available on inappropriate drug dosing in those with dementia or cognitive impairment and renal impairment. Objectives: We aimed to examine the prevalence of, and factors associated with, inappropriate drug dosing in older patients with dementia or cognitive impairment and renal impairment. Methods: We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline and the Cochrane Handbook for Systematic Reviews of Interventions. We searched Medline, Embase, CINAHL, and PubMed for studies on inappropriate drug dosing in older patients with dementia or cognitive impairment and renal impairment, published from 1 January 2000 to 31 August 2024, with English language restriction following the PICOS search strategy. Two reviewers independently screened all titles and abstracts, extracted data from included studies, and undertook quality assessment using the Joanna Briggs Institute (JBI) tool. Descriptive statistics were used to summarise and present findings. Results: In total, eight retrospective cohort studies were included. Of the total number of patients with dementia who had renal impairment (n = 5250), there were 2695 patients (51.3%; range: 0-60%) who had inappropriate drug dosing. Drugs commonly prescribed in inappropriate doses in patients with dementia who had renal impairment included memantine, baclofen, nonsteroidal anti-inflammatory drugs (NSAIDs), metformin, digoxin, morphine, and allopurinol. The studies did not identify statistically significant risk factors for inappropriate drug dosing. Conclusions: Inappropriate drug dosing among older adults with dementia or cognitive impairment and renal impairment appears to occur frequently. While our findings should be interpreted with caution owing to the small number of studies and substantial heterogeneity, proactive prevention, recognition, and management of inappropriate drug dosing in this population is warranted.

Effect of Switching the Histamine-1 Receptor Antagonist Clemastine to Cetirizine in Paclitaxel Premedication Regimens: The H1-Switch Study

PURPOSE

Premedication, including a histamine-1 receptor (H1) antagonist, is recommended to all patients treated with paclitaxel chemotherapy to reduce the incidence of hypersensitivity reactions (HSRs). However, the scientific basis for this premedication is not robust, which provides opportunities for optimization. Substitution of intravenously administered first-generation H1 antagonist for orally administered second-generation H1 antagonist could reduce side effects, and improve efficiency and sustainability. This study investigates the efficacy and safety of substituting intravenous clemastine for oral cetirizine as prophylaxis for paclitaxel-induced HSRs.

METHODS

This single-center, prospective, noninferiority study compares a historic cohort receiving a premedication regimen with intravenous clemastine to a prospective cohort receiving oral cetirizine. Primary end point of the study is HSR grade ≥3. The difference in incidence was calculated together with the 90% CI. We determined that the two-sided 90% CI of HSR grade ≥3 incidence in the oral cetirizine cohort should not be more than 4% higher (ie, the noninferiority margin) compared with the intravenous clemastine cohort.

RESULTS

Two hundred and twelve patients were included in the oral cetirizine cohort (June 2022 and May 2023) and 183 in the intravenous clemastine cohort. HSR grade ≥3 incidence was 1.6% (n = 3) in the intravenous clemastine cohort and 0.5% (n = 1) in the oral cetirizine cohort, resulting in a difference of -1.2% (90% CI, -3.4 to 1.1).

CONCLUSION

Premedication containing oral cetirizine is as safe as premedication containing intravenous clemastine in preventing paclitaxel-induced HSR grade ≥3. These findings could contribute to optimization of care for patients and improve efficiency and sustainability.

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.

International consensus statement on allergy and rhinology: Allergic rhinitis - 2023

BACKGROUND

In the 5 years that have passed since the publication of the 2018 International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis (ICAR-Allergic Rhinitis 2018), the literature has expanded substantially. The ICAR-Allergic Rhinitis 2023 update presents 144 individual topics on allergic rhinitis (AR), expanded by over 40 topics from the 2018 document. Originally presented topics from 2018 have also been reviewed and updated. The executive summary highlights key evidence-based findings and recommendation from the full document.

METHODS

ICAR-Allergic Rhinitis 2023 employed established evidence-based review with recommendation (EBRR) methodology to individually evaluate each topic. Stepwise iterative peer review and consensus was performed for each topic. The final document was then collated and includes the results of this work.

RESULTS

ICAR-Allergic Rhinitis 2023 includes 10 major content areas and 144 individual topics related to AR. For a substantial proportion of topics included, an aggregate grade of evidence is presented, which is determined by collating the levels of evidence for each available study identified in the literature. For topics in which a diagnostic or therapeutic intervention is considered, a recommendation summary is presented, which considers the aggregate grade of evidence, benefit, harm, and cost.

CONCLUSION

The ICAR-Allergic Rhinitis 2023 update provides a comprehensive evaluation of AR and the currently available evidence. It is this evidence that contributes to our current knowledge base and recommendations for patient evaluation and treatment.

Diphenhydramine: Time to Move on?

Diphenhydramine is one of the most widely available, longest-used antihistamine medications but has many side effects including sedation and risk of toxicity in overdose including cardiac toxicity. It is frequently inappropriately used when newer, more favorable antihistamine medications are available. Second-generation antihistamines are also widely available and affordable, with many of the same desired effects as diphenhydramine and fewer, if any, of the undesirable side effects. Because of the negative side effects and wide availability of alternative antihistamine medications, it is definitively time to move on from diphenhydramine.

Unintentional cetirizine overdose causing anticholinergic syndrome: A case report

The incidence of anticholinergic syndrome due to second generation antihistamines is infrequently reported. Largely due to their decreased affinity for central nervous system (CNS) receptors, second generation antihistamines are rarely associated with anticholinergic symptoms, though toxicity is still possible particularly when taken in excess. We report a case of a six year old boy who presented with agitation, hallucinations, fixed and dilated pupils, tachycardia, and hyperthermia consistent with anticholinergic toxicity several hours after accidental overdose of a second generation antihistamine, cetirizine. Early identification of this rare phenomenon is important not only for appropriate emergency management but also for avoidance of potentially invasive and unnecessary tests which may further increase patient morbidity.

Parameters of cardiac symptoms in young athletes using the Heartbytes database

Introduction: To determine clinical parameters that are related to abnormal cardiac symptoms in physically active youth. Methods: We used Simon's Heart Heartbytes National Youth Cardiac Registry to collect data from adolescent athletes in southeastern Pennsylvania. We collected age, race/ethnicity, abnormal cardiac symptoms, medical history, medication use, caffeine intake, and family history. We obtained height, weight, blood pressure, cardiac murmur findings, and ECGs. Echocardiogram was obtained if necessary. Binary logistic regression analysis was performed to identify independent associations between abnormal cardiac symptoms and collected variables. The odds ratio (OR), 95% confidence interval (95% CI), and p-values were used as statistical values. Results: Of the 887 athletes (543 males and 344 females, age = 16.9 ± 2.1 years, height = 166.9 ± 11.4 cm, weight = 62.0 ± 16.0 kg), 186 (21%) had abnormal cardiac symptoms including chest pain, passing out, difficulty breathing, extreme fatigue, and heart race. There was an independent association between abnormal symptoms and a past medical history (OR: 4.77, 95%CI: 3.18, 7.17, p = 0.001) and medication use (OR: 1.74, 95%CI: 1.08, 2.79, p = 0.022). In medical history, young athletes with asthma showed a greater propensity of abnormal cardiac symptoms (48.9%) compared to young athletes without (14.0%, p = 0.001). Additionally, young athletes with anxiety or depression demonstrated a higher proportion of abnormal cardiac symptoms (48.9%) than those without (19.5%, p = 0.001). Although the association between the presence of abnormal symptoms and African-American race (OR: 2.04, 95%CI: 0.96, 4.35, p = 0.065) and average daily consumption of at least 2 caffeine drinks (OR: 2.08, 95%CI: 0.86, 5.02, p = 0.103) were not significant, there was a trend to reach the a priori significance level. Conclusions: This study identified several clinical parameters that are associated with symptoms suggestive of abnormal cardiac conditions. Larger studies need to be done to better sort out the clinical history that may contribute to false positives to further reduce false positives at heart screenings.

Vegetal diamine oxidase alleviates histamine-induced contraction of colonic muscles

Excess of histamine in gut lumen generates a pronounced gastrointestinal discomfort, which may include diarrhea and peristalsis dysfunctions. Deleterious effects of histamine can be alleviated with antihistamine drugs targeting histamine receptors. However, many antihistamine agents come with various undesirable side effects. Vegetal diamine oxidase (vDAO) might be a relevant alternative owing to its histaminase activity. Mammalian intestinal mucosa contains an endogenous DAO, yet possessing lower activity compared to that of vDAO preparation. Moreover, in several pathological conditions such as inflammatory bowel disease and irritable bowel syndrome, this endogenous DAO enzyme can be lost or inactivated. Here, we tested the therapeutic potential of vDAO by focusing on the well-known effect of histamine on gut motility. Using ex vivo and in vitro assays, we found that vDAO is more potent than commercial anti-histamine drugs at inhibiting histamine-induced contraction of murine distal colon muscles. We also identified pyridoxal 5′-phosphate (the biologically active form of vitamin B6) as an effective enhancer of vDAO antispasmodic activity. Furthermore, we discovered that rectally administered vDAO can be retained on gut mucosa and remain active. These observations make administration of vDAO in the gut lumen a valid alternative treatment for histamine-induced intestinal dysfunctions.

Towards definitive management of allergic rhinitis: best use of new and established therapies

BACKGROUND

Allergic rhinitis (AR) is an inflammatory disease of the nasal mucosa impacting up to 25% of Canadians. The standard of care for AR includes a treatment plan that takes into account patient preferences, the severity of the disease, and most essentially involves a shared decision-making process between patient and provider.

BODY

Since their introduction in the 1940s, antihistamines (AHs) have been the most utilized class of medications for the treatment of AR. First-generation AHs are associated with adverse central nervous system (CNS) and anticholinergic side effects. On the market in the 1980s, newer generation AHs have improved safety and efficacy. Compared to antihistamines, intranasal corticosteroids (INCS) have significantly greater efficacy but longer onset of action. Intranasal AH and INCS combinations offer a single medication option that offers broader disease coverage and faster symptom control. However, cost and twice-per-day dosing remain a major limitation. Allergen immunotherapy (AIT) is the only disease-modifying option and can be provided through subcutaneous (SCIT) or sublingual (SLIT) routes. While SCIT has been the definitive management option for many years, SLIT tablets (SLIT-T) have also been proven to be safe and efficacious.

CONCLUSION

There is a range of available treatment options for AR that reflect the varying disease length and severity. For mild to moderate AR, newer generation AHs should be the first-line treatment, while INCS are mainstay treatments for moderate to severe AR. In patients who do not respond to INCS, a combination of intranasal AH/INCS (AZE/FP) should be considered, assuming that cost is not a limiting factor. While SCIT remains the option with the most available allergens that can be targeted, it has the potential for severe systemic adverse effects and requires weekly visits for administration during the first 4 to 6 months. SLIT-T is a newer approach that provides the ease of being self-administered and presents a reduced risk for systemic reactions. In any case, standard care for AR includes a treatment plan that takes into account disease severity and patient preferences.

Using Patient Profiles To Guide The Choice Of Antihistamines In The Primary Care Setting In Malaysia: Expert Consensus And Recommendations

H1-antihistamines are recognized to be effective for conditions such as allergic rhinitis and chronic spontaneous urticaria. However, management of such conditions in the real-world primary care setting may be challenging due to diverse patient-specific considerations, the wide range of antihistamines available, choice of other treatment modalities, and the complexity of interpreting specialist treatment algorithms. Despite regular updates to international guidelines, regional/national surveys of healthcare professionals show a clear gap between guidelines and real-world practice, particularly at the primary care level. This article thus presents the consensus opinion of experts from relevant specialties in Malaysia - allergology, pediatrics, otorhinolaryngology, and dermtology - on harmonizing the use and choice of antihistamines in primary care. Patient profiling is recommended as a tool to guide primary care practitioners in prescribing the appropriate antihistamine for each patient. Patient profiling is a three-step approach that involves 1) identifying the individual's needs; 2) reviewing patient-specific considerations; and 3) monitoring treatment response and referral to specialists in more severe or difficult-to-treat cases. Concurrently, guidelct 3ines should be reviewed and updated periodically to include recommendations that are easily actionable for primary care practitioners.

CSACI position statement: Newer generation H1-antihistamines are safer than first-generation H1-antihistamines and should be the first-line antihistamines for the treatment of allergic rhinitis and urticaria

Oral H₁-antihistamines (AHs) are the most commonly used therapy to treat allergic rhinitis and chronic urticaria. Older, first-generation AHs (e.g. diphenhydramine, hydroxyzine) have significant and common side effects including sedation, impairment with decreased cognitive function, poor sleep quality, dry mouth, dizziness, and orthostatic hypotension. These drugs have also been found to result in death from accidents, intentional or unintentional overdoses, and sudden cardiac death. The unfavourable risk–benefit profile of first-generation AHs led to the development of newer, less-sedating second- and third-generation AHs, which first became available in Canada in the 1980s. High-quality trials have proven that newer generation AHs are superior in safety compared to older first-generation AHs. On average, they have improved potency and efficacy. Second- and third-generation AHs are the recommended first-line treatment for mild allergic rhinitis and acute and chronic urticaria. Despite this evidence, older first-generation AHs continue to be over-utilized because of their over-the-counter (OTC) status and long history of use. The Canadian Society of Allergy Clinical Immunology (CSACI) recommends that newer generation AHs should be preferred over first-generation AHs for the treatment of allergic rhino-conjunctivitis and urticaria. To promote this recommendation, education of health professionals and the public is necessary. Further, given the dangers of older first-generation AHs, we believe they should be used only as a last resort with eventual consideration given to having them only available behind the counter in pharmacies.

Comparative study of the effect of bilastine and cetirizine on cognitive functions at ground level and at an altitude of 4,000 m simulated in hypobaric chamber: a randomized, double-blind, placebo-controlled, cross-over study

INTRODUCTION

Antihistamines are easily accessible and cover the vast majority of the medical therapy of allergic rhinitis. However, their systemic administration may more frequently associate with their well-known side-effect, sedation, which is a serious problem in persons in safety-critical jobs such as aviation. We have a poor understanding whether a non-sedative antihistamine has an impact on vigilance when hypobaric hypoxia occurs during flight.

METHODS

In this randomized, placebo-controlled, double-blind, cross-over study the effect of 20 mg bilastine was compared to 10 mg cetirizine and to placebo (20 mg pyridoxine) in 33 individuals at ground level and at 4,000 m altitude simulated in hypobaric chamber. Levels of vigilance, ultrashort memory, combined distributive attention, monotony tolerance and peripheral blood oxygen saturation (SpO₂) were assessed.

RESULTS

Bilastine did not impair the tested abilities in comparison with the control groups either at ground level or hypobaric hypoxia. Administration of cetirizine increased the number of errors at ground level. At the simulated altitude, already impaired results were additionally demonstrated with regards to the distributive attention test.

CONCLUSIONS

From the two examined antihistamines, bilastine should be the preferred medication for by individuals who require constant attention and are exposed to hypobaric hypoxia.

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.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis

BACKGROUND

Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR).

METHODS

Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR.

CONCLUSION

This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

Prescription medicine use by pedestrians and the risk of injurious road traffic crashes: A case-crossover study

BACKGROUND

While some medicinal drugs have been found to affect driving ability, no study has investigated whether a relationship exists between these medicines and crashes involving pedestrians. The aim of this study was to explore the association between the use of medicinal drugs and the risk of being involved in a road traffic crash as a pedestrian.

METHODS AND FINDINGS

Data from 3 French nationwide databases were matched. We used the case-crossover design to control for time-invariant factors by using each case as its own control. To perform multivariable analysis and limit false-positive results, we implemented a bootstrap version of Lasso. To avoid the effect of unmeasured time-varying factors, we varied the length of the washout period from 30 to 119 days before the crash. The matching procedure led to the inclusion of 16,458 pedestrians involved in an injurious road traffic crash from 1 July 2005 to 31 December 2011. We found 48 medicine classes with a positive association with the risk of crash, with median odds ratios ranging from 1.12 to 2.98. Among these, benzodiazepines and benzodiazepine-related drugs, antihistamines, and anti-inflammatory and antirheumatic drugs were among the 10 medicines most consumed by the 16,458 pedestrians. Study limitations included slight overrepresentation of pedestrians injured in more severe crashes, lack of information about self-medication and the use of over-the-counter drugs, and lack of data on amount of walking.

CONCLUSIONS

Therapeutic classes already identified as impacting the ability to drive, such as benzodiazepines and antihistamines, are also associated with an increased risk of pedestrians being involved in a road traffic crash. This study on pedestrians highlights the necessity of improving awareness of the effect of these medicines on this category of road user.

Effectiveness and safety of combination treatment of herbal medicines and oral antihistamines for atopic dermatitis: a retrospective chart review

BACKGROUND

Patients with atopic dermatitis (AD) exhibit various symptoms, especially itching. Recently, herbal medicines (HMs) are being used in combination with antihistamines for the treatment of AD in Korea. While oral antihistamines can alleviate itching, HMs appear to exert anti-inflammatory effects with minimal side effects. However, there is little evidence regarding the effectiveness and safety of using HMs in combination with antihistamines for AD.

METHODS

To observe the effectiveness and safety of combination treatment with HMs and antihistamines, we performed a retrospective chart review of inpatients with AD who received this combination treatment for at least 7 days in a hospital.

RESULTS

Of 163 inpatients, 40 met the inclusion criteria. All patients received HMs three times, and one or two antihistamines, a day after HM intake. A large proportion of patients received first-generation antihistamines. HMs comprised a mixture of an average of 20.69 different herbs in decoction. The mean total, objective, and subjective SCORing Atopic Dermatitis scores showed a significant decrease after combination treatment. Changes in the mean levels of aspartate transaminase, alanine transaminase, blood urea nitrogen, and creatinine were not statistically significant among treatments. There were no adverse events of pseudoaldosteronism or interstitial pneumonia.

CONCLUSION

We observed that the short-term use of HMs in combination with oral antihistamines was safe and effective, with a low risk of adverse reactions. This study was limited by its retrospective design, and prospective studies with long-term follow-up periods are warranted to further elucidate the safety of this combination treatment for AD.

A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki-Miyaura cross-coupling reaction

A series of differently substituted 3,5-diaryl-2,4,6-trimethylpyridines were prepared and characterized using the Suzuki-Miyaura coupling reaction with accordingly selected bromo-derivatives and arylboronic acids. The reaction conditions were carefully optimized allowing high yield of isolated products and also the construction of unsymmetrically substituted diarylpyridines, difficult to access by other methods.

Placebo-controlled assessment of somnolence effect of cetirizine: a meta-analysis

BACKGROUND

It has been found that the most common adverse reaction which occurs more frequently on cetirizine than on placebo is somnolence. However, the somnolence rate varied widely among different studies. The objective of this study was to assess the somnolence effect of cetirizine 10 mg daily compared to placebo in patients aged 6 years and older using meta-analysis and explore the sources of heterogeneity among different studies.

METHODS

Databases were searched for randomized controlled trials (RCTs) of cetirizine published before 2015. Overall risk differences (RDs) were determined by meta-analyses of 13 trials using the DerSimonian and Laird (D&L) method based on fixed-effects and random-effect models, respectively. The Q statistic, H statistic, and I(2) were calculated for heterogeneity analysis. Subgroup analysis, Galbraith plot, sensitivity analysis, and meta-regression were also performed to explore the sources of heterogeneity.

RESULTS

Various analyses showed that heterogeneity existed among the 13 trials and the placebo run-in period was the cause of heterogeneity. For RCTs without and with placebo run-in period, the overall RDs were 6.51% (95% CI, 4.47% to 8.56%) and 1.03% (95% CI, -0.13% to 2.19%), respectively, which indicated that the difference in somnolence rate between cetirizine 10 mg daily and placebo was not statistically significant for the subgroup with placebo run-in.

CONCLUSION

The meta-analysis showed that the RDs between cetirizine 10 mg daily and placebo on somnolence rate were different for studies with and without a placebo run-in period. The results for studies with a placebo run-in period suggested that cetirizine 10 mg daily has no somnolence effect compared to placebo.

Why are second-generation H1-antihistamines minimally sedating?

H1-antihistamines are widely used in treating allergic disorders, e.g., conjunctivitis, urticaria, dermatitis and asthma. The first-generation H1-antihistamines have a much greater sedative effect than the second-generation H1-antihistamines. Researchers could not offer a satisfactory explanations until late 1990s when studies showed that second-generation H1-antihistamines were substrates of P-glycoprotein. P-glycoprotein, expressed in the blood-brain barrier, acts as an efflux pump to decrease the concentration of H1-antihistamines in the brain, which minimizes drug effects on the central nervous system and results in less sedation. P-glycoprotein is found in the apical side of the epithelium. It consists of transmembrane domains that bind substrates/drugs and nucleotide-binding domains that bind and hydrolyze ATP to generate energy for the drug efflux. This review mainly discusses interactions between P-glycoprotein and commonly used second-generation H1-antihistamines. In addition, it describes other possible determining factors of minimal sedating properties of second-generation H1-antihistamines.

Pharmacology of antihistamines

H1-antihistamines, the mainstay of treatment for urticaria, were developed from anticholinergic drugs more than 70 years ago. They act as inverse agonists rather than antagonists of histamine H1-receptors which are members of the G-protein family. The older first generation H1-antihistamines penetrate readily into the brain to cause sedation, drowsiness, fatigue and impaired concentration and memory causing detrimental effects on learning and examination performance in children and on impairment of the ability of adults to work and drive. Their use should be discouraged. The newer second-generation H1-antihistamines are safer, cause less sedation and are more efficacious. Three drugs widely used for symptomatic relief in urticaria, desloratadine, levocetirizine and fexofenadine are highlighted in this review. Of these levocetirizine and fexofenadine are the most potent in humans in vivo. However, levocetirizine may cause somnolence in susceptible individuals, whereas fexofenadine has a relatively short duration of action and may be required to be given twice daily for all round daily protection. Although desloratadine is less potent, it has the advantages of rarely causing somnolence and having a long duration of action.

Pharmacology of antihistamines

This article reviews the molecular biology of the interaction of histamine with its H1-receptor and describes the concept that H1-antihistamines are not receptor antagonists but are inverse agonists i.e. they produce the opposite effect on the receptor to histamine. It then discourages the use of first-generation H1-antihistamines in clinical practice today for two main reasons. First, they are less effective than second generation H1-antihistamines. Second, they have unwanted side effects, particularly central nervous system and anti-cholinergic effects, and have the potential for causing severe toxic reactions which are not shared by second-generation H1-antihistamines. There are many efficacious and safe second-generation H1-antihistamines on the market for the treatment of allergic disease. Of the three drugs highlighted in this review, levocetirizine and fexofenadine are the most efficacious in humans in vivo. However, levocetirizine may cause somnolence in susceptible individuals while fexofenadine has a relatively short duration of action requiring twice daily administration for full all round daily protection. While desloratadine is less efficacious, it has the advantages of rarely causing somnolence and having a long duration of action. Lastly, all H1-antihistamines have anti-inflammatory effects but it requires regular daily dosing rather than dosing 'on-demand' for this effect to be clinically demonstrable.

Pharmacology of antihistamines

This article reviews the molecular biology of the interaction of histamine with its H₁-receptor and describes the concept that H₁-antihistamines are not receptor antagonists but are inverse agonists i.e. they produce the opposite effect on the receptor to histamine. It then discourages the use of first-generation H₁-antihistamines in clinical practice today for two main reasons. First, they are less effective than second generation H₁-antihistamines. Second, they have unwanted side effects, particularly central nervous system and anti-cholinergic effects, and have the potential for causing severe toxic reactions which are not shared by second-generation H₁-antihistamines. There are many efficacious and safe second-generation H₁-antihistamines on the market for the treatment of allergic disease. Of the three drugs highlighted in this review, levocetirizine and fexofenadine are the most efficacious in humans in vivo. However, levocetirizine may cause somnolence in susceptible individuals while fexofenadine has a relatively short duration of action requiring twice daily administration for full all round daily protection. While desloratadine is less efficacious, it has the advantages of rarely causing somnolence and having a long duration of action. Lastly, all H₁-antihistamines have anti-inflammatory effects but it requires regular daily dosing rather than dosing 'on-demand' for this effect to be clinically demonstrable.

Safety considerations in the management of allergic diseases: focus on antihistamines

OBJECTIVE

To conduct a systematic review of evidence supporting the safety profiles of frequently used oral H(1)-antihistamines (AHs) for the treatment of patients with histamine-release related allergic diseases, e.g. allergic rhinitis and urticaria, and to compare them to the safety profiles of other medications, mostly topical corticosteroids and leukotriene antagonists (LTRA).

RESEARCH DESIGN AND METHODS

Systematic search of the published literature (PubMed) and of the regulatory authorities databases (EMA and FDA) for oral AHs.

RESULTS

Similarly to histamine, antihistamines (AHs) have organ-specific efficacy and adverse effects. The peripheral H(1)-receptor (PrH1R) stimulation leads to allergic symptoms while the brain H(1)-receptor (BrH1R) blockade leads to somnolence, fatigue, increased appetite, decreased cognitive functions (impaired memory and learning), seizures, aggressive behaviour, etc. First-generation oral AHs (FGAHs) inhibit the effects of histamine not only peripherally but also in the brain, and additionally have potent antimuscarinic, anti-α-adrenergic and antiserotonin effects leading to symptoms such as visual disturbances (mydriasis, photophobia, and diplopia), dry mouth, tachycardia, constipation, urinary retention, agitation, and confusion. The somnolence caused by FGAHs interferes with the natural circadian sleep-wake cycle and therefore FGAHs are not suitable to be used as sleeping pills. Second-generation oral AHs (SGAHs) have proven better safety and tolerability profiles, much lower proportional impairment ratios, with at least similar if not better efficacy, than their predecessors. Only SGAHs, and especially those with a proven long-term (e.g., ≥12 months) clinical safety, should be prescribed for young children. Evidence exist that intranasally applied medications, like intranasal antihistamines, have the potential to reach the brain and cause somnolence.

CONCLUSIONS

Second-generation oral antihistamines are the preferred first-line treatment option for allergic rhinitis and urticaria. Patients taking SGAHs report relatively little and mild adverse events even after long-term continuous treatments. An antihistamine should ideally possess high selectivity for the H(1)-receptor, high PrH1R occupancy and low to no BrH1R occupancy.

Intranasal steroids in the treatment of allergy-induced rhinorrhea

While nasal congestion has been identified as one of the most bothersome and prevalent symptoms of allergic rhinitis, it is underappreciated that many patients find rhinorrhea also to be bothersome. Rhinorrhea as a symptom of allergic rhinitis virtually never occurs alone; about 97% of patients with allergic rhinitis suffer from at least two symptoms, a finding that underscores the advantage of treating a broad range of symptoms with a single medication. Along with sneezing and nasal obstruction, rhinorrhea is a classic acute symptom of allergic rhinitis; it appears as a late-phase symptom as well. In this review, the characterization and epidemiology of rhinorrhea, the pathophysiology of rhinorrhea in allergic rhinitis, the roles played by mediators in early- and late-phase rhinorrhea, the prevalence and impact of this symptom, and the efficacy and safety of available treatment options are all discussed in context of relevant literature. A review of the clinical studies assessing the efficacy of intranasal corticosteroids (INS) for rhinorrhea is presented. Many clinical studies and several meta-analyses conclusively demonstrate that, in addition to being safe and well-tolerated, INS are more effective than other agents (including oral and intranasal antihistamines) across the spectrum of AR symptoms, including rhinorrhea and nasal congestion.

Safety and efficacy of bilastine: a new H(1)-antihistamine for the treatment of allergic rhinoconjunctivitis and urticaria

INTRODUCTION

New H(1)-antihistamines should be effective in relieving the symptoms of allergic disease, should have a rapid onset and long duration of action and should neither cause sedation nor interact with cytochrome P450. A review of bilastine was undertaken to determine whether this newer H(1)-antihistamine meets these requirements.

AREAS COVERED

A Medline search was conducted to identify preclinical and clinical studies of bilastine. This was supplemented with additional articles or abstracts cited in reference lists and/or obtained from online sources and internal reports supplied by Faes Farma. Review of these data indicated that bilastine has high selectivity for H(1)-receptors, is rapidly and effectively absorbed, undergoes negligible metabolism and is a substrate for P-glycoprotein, which limits its passage across the blood-brain barrier. At the recommended dose of 20 mg, bilastine is non-sedative, does not enhance the effects of alcohol or CNS sedatives, does not impair actual driving tests, shows no cardiotoxicity and has a similar efficacy to other second-generation H(1)-antihistamines in the treatment of allergic rhinoconjunctivitis and urticaria.

EXPERT OPINION

In view of its favorable pharmacological and clinical characteristics, bilastine is likely to have particular benefit in urticaria for which guidelines recommend increasing the dosage of H(1)-antihistamines up to fourfold if standard dosing is ineffective.

Hay fever in adolescents and adults

INTRODUCTION

Hay fever is found throughout the world. Epidemiological evidence suggests considerable geographical variation in its prevalence. Symptoms are caused by an IgE-mediated type 1 hypersensitivity reaction to airborne allergens such as pollen or fungal spores, and may also cause eye, sinus, respiratory, and systemic problems.

METHODS AND OUTCOMES

We conducted a systematic review and aimed to answer the following clinical question: What are the effects of treatments for hay fever in adolescents and adults? We searched: Medline, Embase, The Cochrane Library, and other important databases up to April 2008 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).

RESULTS

We found 211 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.

CONCLUSIONS

In this systematic review we present information relating to the effectiveness and safety of the following interventions: intranasal corticosteroids, oral antihistamines, intranasal antihistamines, oral leukotriene receptor antagonists, systemic corticosteroids, intranasal ipratropium bromide, oral decongestants, and combinations of these treatments.

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.

H1 antihistamines: current status and future directions

In this review, we compare and contrast the clinical pharmacology, efficacy, and safety of first-generation H1 antihistamines and second-generation H1 antihistamines. First-generation H1 antihistamines cross the blood-brain barrier, and in usual doses, they potentially cause sedation and impair cognitive function and psychomotor performance. These medications, some of which have been in use for more than 6 decades, have never been optimally investigated. Second-generation H1 antihistamines such as cetirizine, desloratadine, fexofenadine, levocetirizine, and loratadine cross the blood-brain barrier to a significantly smaller extent than their predecessors. The clinical pharmacology, efficacy, and safety of these medications have been extensively studied. They are therefore the H1 antihistamines of choice in the treatment of allergic rhinitis, allergic conjunctivitis, and urticaria. In the future, clinically advantageous H1 antihistamines developed with the aid of molecular techniques might be available.

The effects of fexofenadine at steady-state on sleep architecture: a study using polysomnography in healthy Korean volunteers

OBJECTIVES

To compare the effects of a first-generation antihistamine, chlorpheniramine, with those of the second-generation antihistamine, fexofenadine, at steady-state, on nocturnal sleep architecture in healthy Korean volunteers using polysomnography and the Multiple Sleep Latency Test. We evaluated whether a genetic polymorphism of multi-drug resistance 1 gene (MDR1) could produce variations in pharmacokinetic and pharmacodynamic parameters of fexofenadine.

DESIGN/METHODS

Ten healthy male volunteers received one capsule of fexofenadine 180 mg once each morning or chlorpheniramine 6 mg (2 mg in the morning and 4 mg after 12 h) for 3 days, in a single-site, randomized, double-blind, two-treatment, multiple-dosing, two-way crossover study, with a washout period of 7 days. Overnight polysomnography was measured on the second night of the treatment period. The Multiple Sleep Latency Test was carried out the next morning. Blood samples were taken for the assessment of fexofenadine pharmacokinetics and MDR1 genotyping on the third day.

RESULTS

Compared with baseline and fexofenadine, chlorpheniramine significantly increased the latency in rapid eye movement (REM) sleep, with no significant decrease in the percentage of REM sleep. No significant change in latency for REM sleep or percentage REM sleep after dosing with fexofenadine was observed. There was no significant change in the daytime sleepiness with fexofenadine and chlorpheniramine. The effects of MDR1 genotypes and haplotypes on the pharmacokinetics and pharmacodynamics of fexofenadine were not significant.

CONCLUSIONS

Our findings suggest that fexofenadine and chlorpheniramine at steady-state have no significant effect on nocturnal sleep variables and daytime sleepiness, when compared to baseline.

Safety of levocetirizine treatment in young atopic children: An 18-month study

There are more than 40 H(1)-antihistamines available worldwide. Most of these medications have never been optimally studied in prospective, randomized, double-masked, placebo-controlled trials in children. The aim was to perform a long-term study of levocetirizine safety in young atopic children. In the randomized, double-masked Early Prevention of Asthma in Atopic Children Study, 510 atopic children who were age 12-24 months at entry received either levocetirizine 0.125 mg/kg or placebo twice daily for 18 months. Safety was assessed by: reporting of adverse events, numbers of children discontinuing the study because of adverse events, height and body mass measurements, assessment of developmental milestones, and hematology and biochemistry tests. The population evaluated for safety consisted of 255 children given levocetirizine and 255 children given placebo. The treatment groups were similar demographically, and with regard to number of children with: one or more adverse events (levocetirizine, 96.9%; placebo, 95.7%); serious adverse events (levocetirizine, 12.2%; placebo, 14.5%); medication-attributed adverse events (levocetirizine, 5.1%; placebo, 6.3%); and adverse events that led to permanent discontinuation of study medication (levocetirizine, 2.0%; placebo, 1.2%). The most frequent adverse events related to: upper respiratory tract infections, transient gastroenteritis symptoms, or exacerbations of allergic diseases. There were no significant differences between the treatment groups in height, mass, attainment of developmental milestones, and hematology and biochemistry tests. The long-term safety of levocetirizine has been confirmed in young atopic children.

Seasonal allergic rhinitis is associated with a detrimental effect on examination performance in United Kingdom teenagers: case-control study

BACKGROUND

Seasonal allergic rhinitis is common globally, and symptoms have been shown to impair learning ability in children in laboratory conditions. Critical examinations in children are often held in the summer during the peak grass pollen season.

OBJECTIVE

To investigate whether seasonal allergic rhinitis adversely impacts examination performance in United Kingdom teenagers.

METHODS

Case-control analysis of 1,834 students (age 15-17 years; 50% girls) sitting for national examinations. Cases were those who dropped 1 or more grades in any of 3 core subjects (mathematics, English, and science) between practice (winter) and final (summer) examinations; controls were those whose grades were either unchanged or improved. Associations between allergic rhinitis symptoms, clinician-diagnosed allergic rhinitis, and allergic rhinitis-related medication use, recorded on examination days immediately before the examination, were assessed using multilevel regression models.

RESULTS

Between 38% and 43% of students reported symptoms of seasonal allergic rhinitis on any 1 of the examination days. There were 662 cases (36% of students) and 1,172 controls. After adjustment, cases were significantly more likely than controls to have had allergic rhinitis symptoms during the examination period (odds ratio [OR], 1.4; 95% CI, 1.1-1.8; P = .002), to have taken any allergic rhinitis medication (OR, 1.4; 95% CI, 1.1-1.7; P = .01), or to have taken sedating antihistamines (OR, 1.7; 95% CI, 1.1-2.8; P = .03).

CONCLUSION

Current symptomatic allergic rhinitis and rhinitis medication use are associated with a significantly increased risk of unexpectedly dropping a grade in summer examinations.

CLINICAL IMPLICATIONS

This is the first time the relationship between symptomatic allergic rhinitis and poor examination performance has been demonstrated, which has significant implications for clinical practice.

Drug dosage in the elderly: dermatological drugs

Drug pharmacokinetics and pharmacodynamics may be altered in the elderly. An important contribution is made by decreased renal function, but biotransformation in the liver may also play a role. Commonly prescribed dermatological drugs such as methotrexate and cetirizine are likely to be eliminated more slowly in the elderly and potentially hepatotoxic drugs such as itraconazole and acitretin should be used with caution. Altered drug distribution as a result of body composition changes can lead to prolonged half-life or higher plasma concentrations of many drugs. Higher prevalence of adverse drug reactions and multidrug regimens, and large interindividual variability in drug response make drug dosage and administration in the elderly challenging. New immunobiological agents such as alefacept, efalizumab and etanercept, which are approved for treatment of psoriasis, seem to be as well tolerated in the elderly as in younger patients. A recommended approach when prescribing drugs to the elderly would be to start with a small initial dose and to reduce the number of drugs administered simultaneously. It is crucial to simplify the drug regimen as much as possible in order to enhance drug management in the elderly. To improve pharmacotherapy in the elderly, we review age-related changes in pharmacokinetics that are likely to play a role in dermatological practice.

Desloratadine for chronic idiopathic urticaria: a review of clinical efficacy

Chronic idiopathic urticaria (CIU) is a disabling affliction that considerably limits patients' daily activities and interferes with sleep. Clinical studies have shown that histamine H1-receptor antagonists (antihistamines) are highly effective for inhibiting the hives/wheals and pruritus associated with CIU, as well as improving patients' quality of life. Desloratadine is a rapid-acting, once-daily, nonsedating selective H1-receptor antagonist/inverse receptor agonist with proven clinical efficacy in patients with CIU. It has 10-20 times the in vivo H1 receptor-binding affinity of loratadine, its parent compound, and 52-194 times the H1 receptor-binding affinity of cetirizine, ebastine, loratadine, and fexofenadine. Desloratadine displays linear pharmacokinetics after oral administration. Age and sex have no apparent effect on the drug's metabolism and elimination, and food does not affect its bioavailability or absorption. Desloratadine also exerts anti-inflammatory effects via mechanisms that are independent of H1-receptor antagonism. Results from randomized, double-blind, placebo-controlled studies of 6 weeks' duration in adults and adolescents with moderate-to-severe CIU indicate that desloratadine significantly minimizes the severity of pruritus, reduces the number and size of hives, and improves disease-impaired sleep and daily activities. Improvements were noted after a single dose of desloratadine and were maintained over 6 weeks of treatment. Desloratadine was safe and well tolerated in clinical trials of patients with CIU. The adverse effect profile of desloratadine in adults, as well as in children aged from 6 months to 11 years, is comparable to that of placebo. Evaluations of cognitive and psychomotor performance in adults indicate no impairment of function with dosages of desloratadine 5 mg/day. In conclusion, desloratadine is an important therapeutic option for prompt and enduring symptom relief in patients with moderate-to-severe CIU. In addition to efficacy and safety, desloratadine affords a convenient administration regimen, rapid onset of action, and an absence of drug-drug or drug-food interactions. Other important prescribing considerations are that, unlike all first-generation and some second-generation antihistamines, desloratadine is nonsedating at its clinically approved dosage and does not impair psychomotor function.