Comparative onset of action and symptom relief with cetirizine, loratadine, or placebo in an environmental exposure unit in subjects with seasonal allergic rhinitis: confirmation of a test system

Technical standards in allergen exposure chambers worldwide - an EAACI Task Force Report

Allergen exposure chambers (AECs) can be used for controlled exposure to allergenic and non-allergenic airborne particles in an enclosed environment, in order to (i) characterize the pathological features of respiratory diseases and (ii) contribute to and accelerate the clinical development of pharmacological treatments and allergen immunotherapy for allergic disease of the respiratory tract (such as allergic rhinitis, allergic rhinoconjunctivitis, and allergic asthma). In the guidelines of the European Medicines Agency for the clinical development of products for allergen immunotherapy (AIT), the role of AECs in determining primary endpoints in dose-finding Phase II trials is emphasized. Although methodologically insulated from the variability of natural pollen exposure, chamber models remain confined to supporting secondary, rather than primary, endpoints in Phase III registration trials. The need for further validation in comparison with field exposure is clearly mandated. On this basis, the European Academy of Allergy and Clinical Immunology (EAACI) initiated a Task Force in 2015 charged to gain a better understanding of how AECs can generate knowledge about respiratory allergies and can contribute to the clinical development of treatments. Researchers working with AECs worldwide were asked to provide technical information in eight sections: (i) dimensions and structure of the AEC, (ii) AEC staff, (iii) airflow, air processing, and operating conditions, (iv) particle dispersal, (v) pollen/particle counting, (vi) safety and non-contamination measures, (vii) procedures for symptom assessments, (viii) tested allergens/substances and validation procedures. On this basis, a minimal set of technical requirements for AECs applied to the field of allergology is proposed.

Utility of Environmental Exposure Unit Challenge Protocols for the Study of Allergic Rhinitis Therapies

PURPOSE OF REVIEW

This paper explores how the Environmental Exposure Unit (EEU) experimental model can be used to further our understanding of pharmacotherapies and immunotherapies for the treatment of allergic rhinitis (AR).

RECENT FINDINGS

EEUs are used increasingly for the study of combination therapies, immunotherapies, and novel AR treatments. A combined antihistamine/corticosteroid nasal spray formulation was seen to have a faster onset of action relative to the therapies individually in the Environmental Exposure Chamber. House dust mite sublingual immunotherapy tablets are both safe and efficacious as evaluated by the Vienna Challenge Chamber. The Kingston EEU found that a novel peptide-based immunotherapy approach to be effective in reducing grass pollen-induced AR. Lastly, nasal filters were determined to reduce seasonal AR symptoms, given out-of-season in the Denmark Environmental Exposure Unit. EEUs are controlled, replicable models that provide valuable insight into the efficacy, onset and duration of action, and dose-related impacts of AR therapeutics, with direct clinical relevance.

Clinical standardization of two controlled allergen challenge facilities: The Environmental Exposure Unit and the Biogenics Research Chamber

BACKGROUND

Controlled allergen challenge facilities (CACF), in disparate geographic regions with dissimilar engineering and base populations, have historically functioned as single, independent sites in clinical allergy trials. We aimed to demonstrate "between-unit reproducibility" to allow controlled challenge trials of participants using 2 CACFs.

OBJECTIVE

To compare and standardize 2 CACFs located in Kingston, Ontario, Canada, and San Antonio, Texas, by examining participant-reported symptom severity during qualifying and treatment visits and evaluating response to treatment, while using the same allergen.

METHODS

At 2 different CACFs, participants were enrolled in a double-blind, placebo-controlled, crossover intervention trial with cetirizine 10 mg. Different distribution devices delivered common short ragweed pollen via laminar air flow and maintained an airborne concentration of 3500 ± 700 grains/m³ in both facilities. A 1-hour "sham" run with no pollen release preceded a priming exposure of 3 hours and was followed 3 days later by a qualifying/treatment 5-hour exposure. At least 14 days later, another priming exposure was followed by the crossover exposure and treatment.

RESULTS

Forty-eight and 43 subjects completed the study at Kingston and San Antonio, respectively. Demographics were similar. Fewer than 10% exhibited symptoms with sham exposure. No significant differences were found between the 2 facilities in maximal total rhinoconjunctivitis symptom score, total nasal symptom score, and total ocular symptom score, nor in areas under the curve. In both facilities, no significant effects of cetirizine 10 mg over placebo were detected.

CONCLUSION

The results were equivalent, demonstrating that the 2 CACFs can be used together in dual-center clinical trials and show the possibility of multicenter trials involving multiple CACFs.

[Environmental exposure chambers (EEC): A novel tool for pathophysiological and pharmaceutical research]

Airborne allergic diseases (allergic asthma, rhinitis and conjunctivitis) have reached epidemic proportions and are a great burden for both society and individuals. Therefore we need to better understand the physiopathological mechanisms and to increase clinical research in these diseases. However, traditional outpatient studies are difficult and have number of limitations, in particular the variability of allergen exposure. Yet allergen provocation tests, especially bronchial challenges in asthma, are excellent tools to measure the efficiency of anti-allergic therapies. Environmental exposure chambers (EEC) allow the performance of controlled allergen provocation tests on a large scale with remarkable sensitivity, specificity and reproducibility. Moreover, they allow a precise collection of allergic symptoms, making them interesting tools for patho-physiological and clinical studies. During the last thirty years, they have assisted the study of anti-allergic therapies and provided data on their pharmacodynamic characteristics, particularly in allergic rhinitis. However, there are still no EEC tests centered on asthma. The EEC of Strasbourg (ALYATEC^®) was developed to fulfill two objectives: to allow standardized allergenic and non-allergenic exposures with better control of the parameters than in other EEC and to offer a place to study asthma and anti-asthmatic therapies safely.

Onset of Action of Azelastine Nasal Spray Compared with Mometasone Nasal Spray and Placebo in Subjects with Seasonal Allergic Rhinitis Evaluated in an Environmental Exposure Chamber

Background

The objective of this study was to determine the onset of action of azelastine hydrochloride nasal spray compared with placebo and an intranasal steroid, mometasone furoate, in subjects with seasonal allergic rhinitis (SAR).

Methods

Subjects with a history of SAR and symptomatic while exposed to ragweed pollen in an environmental exposure chamber (EEC) were randomized to azelastine nasal spray (n = 150), mometasone nasal spray (n = 150), or placebo (n = 150) and recorded total nasal symptom scores (TNSS), consisting of sneezing, nasal pruritus, rhinorrhea, and congestion, during an 8-hour study period.

Results

Azelastine nasal spray showed a statistically significant improvement in the TNSS at 15 minutes compared with placebo. The effect was durable at each time point during the 8-hour study. Azelastine nasal spray also was significantly more effective than mometasone at each time point.

Conclusion

Azelastine nasal spray has a rapid (15 minute) onset of action. Azelastine nasal spray was superior to both placebo and mometasone nasal spray in reducing nasal symptoms of SAR occurring within 8 hours after an allergen challenge.

Onset of Action of the Fixed Combination Intranasal Azelastine-Fluticasone Propionate in an Allergen Exposure Chamber

BACKGROUND

A fixed-dose combination of intranasal azelastine hydrochloride and fluticasone propionate (MP-AzeFlu) is the most effective treatment of allergic rhinitis, but its onset of action requires further investigation.

OBJECTIVE

To compare the onset of action of MP-AzeFlu with the free combination of oral loratadine (LORA) and intranasal fluticasone propionate (INFP).

METHODS

In this single-center, randomized, placebo-controlled, double-blind, double-dummy, 3-period crossover trial, allergic rhinitis symptoms were induced in asymptomatic patients by ragweed pollen challenge in an allergen environmental exposure chamber. Patients received single-dose MP-AzeFlu, LORA/INFP, or placebo and were monitored for 4 hours. The primary outcome was onset of action measured by total nasal symptom score (TNSS). Secondary measures were total ocular symptom score (TOSS), total score of the 7 nasal and ocular symptoms (T7SS), and the global visual analog scale (VAS).

RESULTS

The full analysis set included 82 patients, of which 78 completed all treatments. TNSS was significantly reduced versus placebo from 5 minutes for MP-AzeFlu and 150 minutes for LORA/INFP onward (both P < .05) till the end of assessment (0-4 hours). MP-AzeFlu reduced TNSS to a greater extent at each time point from 5 to 90 minutes (P < .05) and over the entire assessment interval (P ≤ .005) versus LORA/INFP or placebo. No statistically significant difference between LORA/INFP and placebo was observed over the assessment interval (P = .182). The onset of action of MP-AzeFlu assessed by TOSS, T7SS, and VAS was 10 minutes, 2 hours earlier than with LORA/INFP.

CONCLUSION

MP-AzeFlu had a more rapid onset of action (5 minutes) and was more effective than LORA/INFP.

Onset of action for loratadine tablets for the symptomatic control of seasonal allergic rhinitis in adults challenged with ragweed pollen in the Environmental Exposure Unit: a post hoc analysis of total symptom score

Background

Loratadine is a second-generation, non-sedating antihistamine used for the relief of allergic rhinitis symptoms. Previous studies reported that when loratadine was encapsulated, the onset of action for symptom relief was 180 min. However, unmodified loratadine tablets were not evaluated at that time. Using data from a previously published Environmental Exposure Unit (EEU) study comparing azelastine nasal spray with loratadine tablets, cetirizine tablets, and placebo, this post hoc analysis determines the onset of action of loratadine tablets (i.e. unmodified) by analyzing the total symptom score for the relief of nasal and ocular seasonal allergic rhinitis (SAR) symptoms.

Methods

A Phase IV, randomized, single-center, double-blind, placebo-controlled, double-dummy, four-way crossover study was conducted in the EEU. Seventy participants were randomized sequentially into one of the four treatments during ragweed pollen exposure. Nasal and ocular symptom scores were self-reported by the participants and recorded. The original study analysis was carried out by evaluating the nasal symptom scores only. For this post hoc analysis, both nasal and ocular data from the loratadine and placebo treatment arms were analyzed. The primary endpoint for this analysis was the onset of action of loratadine as measured by the change in total symptom score (TSS) from baseline in comparison to placebo. The onset of ocular symptom relief using the total ocular symptom score (TOSS) was also reported.

Results

Loratadine tablets demonstrated a significant and durable improvement in both TSS (P = .005) and TOSS (P = .013) at 75 min post-treatment administration compared to placebo. The mean proportion of participants reporting none or mild for all component symptoms of TSS and TOSS at 75 min and thereafter was significantly higher in the loratadine (TSS, P = .0005; TOSS, P ≤ .0001) vs. placebo treatment arm.

Conclusions

The onset of action of loratadine tablets was 75 min for the relief of nasal and ocular symptoms in adults with SAR. These results suggest a faster onset of action for loratadine tablets (75 min) compared to previously reported studies which were conducted with modified (i.e. gelatin-encapsulated) loratadine tablets (180 min).

Trial registration Clinicaltrials.gov identifier NCT00561717

Electronic supplementary material

The online version of this article (10.1186/s13223-017-0227-4) contains supplementary material, which is available to authorized users.

Allergen exposure chambers: harmonizing current concepts and projecting the needs for the future - an EAACI Position Paper

BACKGROUND

Allergen exposure chambers (AECs) are clinical facilities allowing for controlled exposure of subjects to allergens in an enclosed environment. AECs have contributed towards characterizing the pathophysiology of respiratory allergic diseases and the pharmacological properties of new therapies. In addition, they are complementary to and offer some advantages over traditional multicentre field trials for evaluation of novel therapeutics. To date, AEC studies conducted have been monocentric and have followed protocols unique to each centre. Because there are technical differences among AECs, it may be necessary to define parameters to standardize the AECs so that studies may be extrapolated for driving basic immunological research and for marketing authorization purposes by regulatory authorities.

METHODS

For this task force initiative of the European Academy of Allergy and Clinical Immunology (EAACI), experts from academia and regulatory agencies met with chamber operators to list technical, clinical and regulatory unmet needs as well as the prerequisites for clinical validation.

RESULTS

The latter covered the validation process, standardization of challenges and outcomes, intra- and interchamber variability and reproducibility, in addition to comparability with field trials and specifics of paediatric trials and regulatory issues.

CONCLUSION

This EAACI Position Paper aims to harmonize current concepts in AECs and to project unmet needs with the intent to enhance progress towards use of these facilities in determining safety and efficacy of new therapeutics in the future.

Optimal Duration of Allergic Rhinitis Clinical Trials

OBJECTIVE: Guidelines have been published by the Food and Drug Administration (FDA) and the European Agency for the Evaluation of Medicinal Products (EMEA) for the conduct of seasonal allergic rhinitis (SAR) and perennial allergic rhinitis (PAR) studies. These guidelines have differences regarding the duration of such trials: the FDA suggests 2 weeks for SAR and 4 weeks for PAR but the EMEA suggests 2 to 4 weeks for SAR and 6 to 12 weeks for PAR trials. In the interest of global harmonization, it would be desirable to have a uniform duration of such trials so that investigators, internationally, would be able to readily compare results for various types of treatments based on a single standard. Therefore, we performed an evidence-based review to answer the clinical question, What is the optimal duration for SAR and PAR clinical trials?

METHODS: We performed a MEDLINE search of the published literature from 1995 to the present. We used appropriate search terms, such as allergic rhinitis, seasonal allergic rhinitis, perennial allergic rhinitis, SAR, and PAR, to identify pertinent articles. These articles were reviewed and graded according to the evidence quality.

RESULTS: After an initial screening of more than 300 articles, 138 articles were analyzed thoroughly. No study specifically addressed the question of the optimal duration of SAR or PAR clinical trials.

CONCLUSIONS: We conclude that the current FDA (draft) guidelines calling for a study length of 2 weeks for the assessment of drug efficacy for SAR and 4 weeks for the study of drug efficacy in PAR are appropriate and that longer study periods are not likely to add meaningfully to the assessment of drug efficacy.

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.

Controlled Allergen Challenge Facilities and Their Unique Contributions to Allergic Rhinitis Research

The aim of this study is to review advances in basic and clinical allergic rhinitis (AR) research over the past decade that have been conducted using controlled allergen challenge facility (CACF) models of allergen challenge. Databases, including PubMed, Medline, and Web of Science were searched for articles employing an ambient pollen exposure in a controlled facility to study AR, published between 2004 and the present date, using the terms as follows: CACF, Environmental Exposure Unit (EEU), Vienna Challenge Chamber (VCC), Fraunhofer Institute Environmental Challenge Chamber, Atlanta Allergen Exposure Unit, Biogenics Research Chamber, Allergen BioCube, Chiba and Osaka Environmental Challenge Chamber, exposure unit, challenge chamber, or environmental exposure chamber. Articles were then selected for relevance to the goals of the present review, including important contributions toward clinical and/or basic science allergy research. CACFs offer sensitive, specific, and reproducible methodology for allergen challenge. They have been employed since the 1980s and offer distinct advantages over traditional in-season multicentre trials when evaluating new treatments for AR. They have provided clinically applicable efficacy and pharmacologic information about important allergy medications, including antihistamines, decongestants, antileukotrienes, immunotherapies, and nasal steroids. CACF models have also contributed to basic science and novel/experimental therapy research. To date, no direct studies have been conducted comparing outcomes from one CACF to another. Over the past decade, CACF models have played an essential role in investigating the pathophysiology of AR and evaluating new therapies. The future opportunities for this model continue to expand.

Environmental exposure chambers in allergen immunotherapy trials: Current status and clinical validation needs

As required by the European Medicines Agency and the US Food and Drug Administration for pivotal trials involving allergen immunotherapy (AIT) products, clinical efficacy assessment is currently based on double-blind, placebo-controlled field studies with natural allergen exposure during the allergen season. However, this study design is associated with several drawbacks, such as the high variability of allergen exposure in different trial sites or seasons and the presence of confounding environmental factors. On the contrary, environmental exposure chambers (EECs) aim to operate with a stable and reproducible allergen exposure under highly standardized environmental conditions. Technical validation parameters for different EECs worldwide have been published by several groups. However, full clinical validation of EEC study outcomes is required for their classification as an appropriate alternative to natural allergen exposure for AIT product efficacy assessment. Some clinical validation parameters have already been addressed for EEC units. The reliability of provoked symptoms in repeated EEC sessions is high, but the predictive power of EEC settings for the clinical response on natural exposure and the impact of seasonal priming on test results still have to be validated systematically, as does the inter-EEC variability. Thus the authors recommend a continued in-depth validation of EECs to exploit the potential of this technology for future AIT product development.

Allergic rhinitis is a risk factor for traffic safety

BACKGROUND

Allergic rhinitis (AR) affects up to 30% of the adult population and symptomatic patients continue to engage in daily life activities, including car driving. Previous studies have shown that AR can impair cognitive functions, especially during longer-lasting tasks. Other reports suggest negative effects on psychomotor functions such as driving, but no clear evidence has been presented yet.

OBJECTIVES

Primary objective was to determine the effect of AR per se on actual driving performance and compare it with the effects of treated AR.

METHODS

Nineteen patients with documented AR history underwent a unique and validated 1-h on-the-road driving test outside the pollen season. In a 4-leg repeated measures design, patients underwent a nasal provocation test with either pollen or inactive control prior to the driving test. In the three conditions with pollen provocation, patients were pretreated with either cetirizine 10 mg, fluticasone furoate 27.5 μg, or placebo to alleviate the provoked AR symptoms.

RESULTS

The driving performance of patients when symptomatic and not treated was significantly impaired compared to the placebo condition. When engaging in a secondary memory task during driving, their performance deteriorated further. The magnitude of impairment was relevant and comparable to that seen at a blood alcohol level of 0.05%, the legal limit in many countries. Treatment of AR symptoms partially counteracted the effect of AR on driving.

CONCLUSIONS

Untreated AR can impair driving ability and put patients at risk. Drug therapy reduces this impairment, and AR patients should therefore be advised to always treat their condition.

The clinical use of cetirizine in the treatment of allergic rhinitis

BACKGROUND

Cetirizine is among the first second-generation H1 antihistamines (SGAHs) developed to provide selective H1 receptor inhibition without central nervous system depression.

OBJECTIVE

The aim of this review is to summarize the amount of data collected over 25 years of clinical use of cetirizine and compare this with data available for other SGAHs in the management of patients with allergic rhinitis (AR).

METHODS

A comprehensive literature search for publications relating to cetirizine was performed using the Pubmed database, and relevant papers published in English were selected for detailed review.

RESULTS

Compared with the majority of other SGAHs, cetirizine was generally shown to have a more favourable pharmacological profile, to be well tolerated, be at least equally or more efficacious in attenuating/inhibiting nasal and ocular symptoms and to improve the quality of life in AR patients. The majority of clinical trials investigating the effect of SGAHs in AR patients further indicated that cetirizine was often employed as the main comparator active drug.

CONCLUSION

Based on the evidence that cetirizine is a commonly employed active comparator drug in AR, it is tempting to suggest that cetirizine may be a suitable benchmark in the development of novel pharmacotherapies for AR.

A four-way, double-blind, randomized, placebo controlled study to determine the efficacy and speed of azelastine nasal spray, versus loratadine, and cetirizine in adult subjects with allergen-induced seasonal allergic rhinitis

Background

Azelastine has been shown to be effective against seasonal allergic rhinitis (SAR). The Environmental Exposure Unit (EEU) is a validated model of experimental SAR. The objective of this double-blind, four-way crossover study was to evaluate the onset of action of azelastine nasal spray, versus the oral antihistamines loratadine 10 mg and cetirizine 10 mg in the relief of the symptoms of SAR.

Methods

70 participants, aged 18-65, were randomized to receive azelastine nasal spray, cetirizine, loratadine, or placebo after controlled ragweed pollen exposure in the EEU. Symptoms were evaluated using the total nasal symptom score (TNSS). The primary efficacy parameter was the onset of action as measured by the change from baseline in TNSS.

Results

Azelastine displayed a statistically significant improvement in TNSS compared with placebo at all time points from 15 minutes through 6 hours post dose. Azelastine, cetirizine, and loratadine reduced TNSS compared to placebo with an onset of action of 15 (p < 0.001), 60 (p = 0.015), and 75 (p = 0.034) minutes, respectively. The overall assessment of efficacy was rated as good or very good by 46% of the participants for azelastine, 51% of the participants for cetirizine, and 30% of the participants for loratadine compared to 18% of the participants for placebo.

Conclusions

Azelastine’s onset of action for symptom relief was faster than that of cetirizine and loratadine. The overall participant satisfaction in treatment with azelastine is comparable to cetirizine and statistically superior to loratadine. These results suggest that azelastine may be preferential to oral antihistamines for the rapid relief of SAR symptoms.

Allergic rhinitis

Familiarity with the diagnosis and management of allergic rhinitis is important for physicians concerned with the nasal airway. Allergic rhinitis is a common and manageable condition that may cause persistent or intermittent symptoms that vary as to duration and severity. Allergic rhinitis impairs quality of life, sleep, school performance, and productivity on a scale that compares with other chronic diseases. Diagnosis is primarily clinical, but supported by allergy testing. Therapeutic options for allergic rhinitis include pharmacotherapy, environmental control, and immunotherapy. More recently, a role for sublingual immunotherapy and turbinate reduction has been reported.

Antihistamine therapy in allergic rhinitis

Antihistamines have long been a mainstay in the therapy for allergic rhinitis. Many different oral antihistamines are available for use, and they are classified as first generation or second generation based on their pharmacologic properties and side-effect profiles. The recent introduction of intranasal antihistamines has further expanded the role of antihistamines in the treatment of allergic rhinitis. Certain patient populations, such as children and pregnant or lactating women, require special consideration regarding antihistamine choice and dosing as part of rhinitis therapy.

Fluticasone furoate versus placebo in symptoms of grass-pollen allergic rhinitis induced by exposure in the Vienna Challenge Chamber

OBJECTIVE

The Vienna Challenge Chamber (VCC) offers a controlled and controllable paradigm in which to reproducibly evaluate the efficacy of anti-allergic treatment. The aim of this study was to assess the efficacy of the novel intranasal corticosteroid fluticasone furoate (FF) in the VCC.

METHODS

The single-centre, randomised, double-blind, placebo-controlled, two-period crossover study was conducted in 59 adult males with grass pollen allergic rhinitis (AR). Patients received either Fluticasone furoate 200 mcg once-daily, or placebo intranasally for 8 days. AR symptoms were induced during 4-hour allergen challenges with grass pollen in the VCC at the end of each 8-day treatment period. A first challenge was conducted at 1-5 hours post-dose, followed by a second challenge at 22-26 hours post-dose. The primary endpoint was total nasal symptom score (TNSS; sum of itch, sneeze, rhinorrhoea, obstruction symptoms assessed on a categorical scale of 0-3) weighted mean over 2-5 hours post-dose. Secondary endpoints included: TNSS weighted mean over 23-26 hours post-dose and global symptom score, eye symptom score, nasal secretions and nasal airflow weighted means over 2-5 and 23-26 hours post-dose.

RESULTS

Fluticasone furoate showed consistent attenuation of AR symptoms in both the early and late challenges. Compared with placebo, weighted mean of TNSS was reduced on average by 4.14 point-scores at 2-5 hours post-dose and 3.63 point scores at 23-26 hours post-dose. These positive effects were also seen across all secondary endpoints.

CONCLUSION

An 8-day treatment course of intranasal FF 200 mcg given once-daily statistically significantly reduced symptoms of AR including associated eye symptoms. Statistical significance was declared where the relevant two-sided 95% confidence interval did not contain zero. This positive effect was sustained over 24 hours suggesting that fluticasone furoate could be efficacious as a once daily steroid.

Combination therapy with azelastine hydrochloride nasal spray and fluticasone propionate nasal spray in the treatment of patients with seasonal allergic rhinitis

BACKGROUND

To our knowledge, there are no published studies that evaluated the efficacy of azelastine hydrochloride nasal spray in combination with an intranasal corticosteroid, although anecdotal reports of the use of these agents in combination are common.

OBJECTIVE

To determine if greater efficacy could be achieved with the intranasal antihistamine azelastine and the intranasal corticosteroid fluticasone propionate used concurrently compared with the efficacy of each agent alone.

METHODS

This randomized, 2-week, multicenter, double-blind trial was conducted during the Texas mountain cedar season. After a 5-day placebo lead-in period, 151 patients with moderate to severe nasal symptoms were randomized to treatment with the following: (1) azelastine nasal spray, 2 sprays per nostril twice daily; (2) fluticasone nasal spray, 2 sprays per nostril once daily; or (3) azelastine nasal spray, 2 sprays per nostril twice daily, plus fluticasone nasal spray, 2 sprays per nostril once daily. The primary efficacy variable was the change from baseline in the total nasal symptom score (TNSS), consisting of sneezing, itchy nose, runny nose, and nasal congestion.

RESULTS

All 3 groups had statistically significant (P < .001) improvements from their baseline TNSS after 2 weeks of treatment. The TNSS improved 27.1% with fluticasone nasal spray, 24.8% with azelastine nasal spray, and 37.9% with the 2 agents in combination (P < .05 vs either agent alone). All 3 treatments were well tolerated.

CONCLUSIONS

The significant improvement in the TNSS with combination therapy relative to the individual agents alone is in contrast to previously published studies that found no advantage with an oral antihistamine and an intranasal corticosteroid in combination. Azelastine nasal spray and fluticasone nasal spray in combination may provide a substantial therapeutic benefit for patients with seasonal allergic rhinitis compared with therapy with either agent alone.

Treatment Options for the Management of Perennial Allergic Rhinitis, with a Focus on Intranasal Corticosteroids

Perennial allergic rhinitis (PAR) can have a significant impact on a patient's quality of life. While allergen avoidance is the first line of management for PAR, complete avoidance is difficult. Therapeutic options available for PAR include intranasal corticosteroids (INS), H1-antihistamines, decongestants and local chromones, as well as immunotherapy. For mild symptoms, INS and antihistamines are the standard of care, whereas for moderate-to-severe PAR, INS are the preferred therapy due to their proven efficacy. Patient quality of life and therapy preference play a role in maintaining adherence to treatment.

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.

Efficacy of diphenhydramine vs desloratadine and placebo in patients with moderate-to-severe seasonal allergic rhinitis

BACKGROUND

Previous studies have shown that diphenhydramine and desloratadine effectively relieve symptoms of seasonal allergic rhinitis (SAR).

OBJECTIVE

To compare the relative efficacy of 50 mg of diphenhydramine hydrochloride, 5 mg of desloratadine, and placebo in relieving symptoms in patients with moderate-to-severe SAR.

METHODS

In this 1-week, multicenter, parallel-group, randomized, double-blind, double-dummy, placebo-controlled study, 610 patients with moderate-to-severe SAR received 50 mg of diphenhydramine hydrochloride 3 times daily, 5 mg of desloratadine once daily, or placebo. Daily 24-hour reflective total nasal symptom scores (TNSSs) (primary end point), total symptom scores, and individual symptom scores were evaluated. A global evaluation of response to treatment was conducted at 2 posttreatment visits.

RESULTS

The mean reduction from baseline in 24-hour reflective TNSSs relative to the placebo response was 77.6% for the diphenhydramine group (P < .001) and 21.0% for the desloratadine group (P = .12). A TNSS between-treatment difference of -1.81 (46.7%; P < .001) was observed when comparing diphenhydramine with desloratadine. A similar between-treatment difference was observed for the 24-hour reflective total symptom score comparing diphenhydramine to desloratadine (-3.35; 45.5%; P < .001). Diphenhydramine provided clinically and statistically significant reductions vs placebo and desloratadine in all individual symptoms, including nasal congestion. Desloratadine had a tendency toward improvement compared with placebo for most individual symptom scores. However, a statistically significant result was reached only for sneezing (-0.27; 33.9%; P = .04).

CONCLUSIONS

Diphenhydramine, 50 mg, given for 1 week provided statistically significant and clinically superior improvements in symptoms compared with 5 mg of desloratadine in patients with moderate-to-severe SAR. Somnolence occurred more frequently with diphenhydramine (22.1%) compared with desloratadine (4.5%) and placebo (3.4%).

Onset of action of a topical antihistamine as assessed by histamine challenge-induced plasma exudation responses

BACKGROUND

Although usually administered orally, antihistamines are available also for topical use in allergic rhinitis. Information on onset of action of these drugs is incomplete.

OBJECTIVE

To examine onset of action of topical cetirizine-dinitrate on plasma exudation evoked by repeated nasal histamine challenges.

METHODS

A liposome formulation of cetirizine-dinitrate (2.44 mg per nasal cavity) was delivered via a nasal spray device as 2 consecutive actuations per nasal cavity in a placebo-controlled design. The nasal mucosal surface was challenged and lavaged with a histamine solution (100 microg/mL) 5, 15, 25, and 55 minutes after each treatment. In addition, the mucosa was lavaged with saline before each treatment. The lavage fluid levels of alpha2-macroglobulin were measured as an index of mucosal exudation (luminal entry) of plasma.

RESULTS

Histamine produced significant increases in nasal lavage fluid levels of alpha2-macroglobulin at all observation points (5 through 55 minutes after treatment). Nasal cetirizine-dinitrate significantly inhibited this response at 5 and 15 minutes after treatment.

CONCLUSIONS

The effect of topical cetirizine-dinitrate, as established by histamine challenge-induced mucosal exudation of plasma, has an early onset (ie, within 5 to 10 minutes).

Experimental models for the evaluation of treatment of allergic rhinitis

OBJECTIVE

To review the experimental models used for the clinical evaluation of treatments for allergic rhinitis.

DATA SOURCES

Peer-reviewed clinical studies and review articles were selected from the PubMed database using the following relevant keywords: allergic rhinitis in combination with efficacy, wheal and flare, nasal challenge, park, cat room, or exposure unit. Regulatory guidance documents on allergic rhinitis were also included.

STUDY SELECTION

The authors' knowledge of the field was used to limit references with emphasis on recent randomized and controlled studies. References of historical significance were also included.

RESULTS

Traditional outpatient studies are universally accepted in the evaluation of treatment for allergic rhinitis. Experimental models provide ancillary information on efficacy at different stages of treatment development. Skin histamine and allergen challenge, as well as direct nasal challenge with histamine and allergen, are often used as early steps in assessing drug efficacy. Exposure units, park settings, and cat rooms better approximate real life by drawing on the natural mode of allergen exposure and delivering the sensitizing allergen to allergic individuals in the ambient air. Park studies make use of allergens in the outdoors, whereas cat rooms and exposure units present the sensitizing allergens indoors, with the latter providing consistent predetermined allergen levels. Exposure unit and park studies are acknowledged for the determination of onset of action and are also suited to the measurement of duration of effect and other measures of efficacy. Onset and duration of effect are 2 important pharmacodynamic properties of antihistamines and nasal corticosteroids as determined by the Allergic Rhinitis and Its Impact on Asthma and the European Academy of Allergology and Clinical Immunology workshop group.

CONCLUSIONS

All challenge models serve as important instruments in the evaluation of antiallergic medications and provide additional information to complement traditional studies.

Treatment for allergic rhinitis and chronic idiopathic urticaria: focus on oral antihistamines

OBJECTIVE

To review the efficacy and safety of first- and newer-generation antihistamines for the management of allergic rhinitis and chronic idiopathic urticaria (CIU), with a focus on management in the pharmacy.

DATA SOURCES

A literature review was performed using MEDLINE (1966-October 2005), with no time or language restrictions. Key words or phrases used were histamine, antihistamine(s), first- and second-generation, allergic rhinitis, chronic idiopathic urticaria, quality of life, impairment, sedation, cost-effectiveness, astemizole, cetirizine, desloratadine, diphenhydramine, fexofenadine, loratadine, hydroxyzine, ketotifen, and mizolastine. Additional references were found in the bibliographies of the articles cited.

STUDY SELECTION AND DATA EXTRACTION

Clinical trials and other experimental studies of the use of antihistamines for the management of allergic rhinitis and CIU were selected. Review papers and guidelines were also included.

DATA SYNTHESIS

First-generation antihistamines are effective at ameliorating the symptoms of allergic rhinitis and CIU; however, they are associated with adverse effects due to a lack of selectivity for the histamine H(1)-receptor and an ability to bind to cerebral H(1)-receptors. Newer-generation agents, in general, possess high H(1)-receptor selectivity and a low tendency to cross the blood-brain barrier, while maintaining efficacy. In general, safety at elevated doses has been demonstrated for the newer antihistamines, although higher rates of sedation and impairment have been reported with increasing doses for some agents.

CONCLUSIONS

Pharmacists can play an important role in the management of allergic rhinitis and CIU by considering the relative advantages of newer-generation agents when reviewing treatment options.

Effectiveness of azelastine nasal spray compared with oral cetirizine in patients with seasonal allergic rhinitis

BACKGROUND

Azelastine nasal spray and oral cetirizine are selective histamine H(1)-receptor antagonists that are approved in the United States for the treatment of seasonal allergic rhinitis (SAR).

OBJECTIVE

The objective of the present study was to compare the efficacy and tolerability of azelastine nasal spray administered at the recommended dosage of 2 sprays per nostril twice daily with those of cetirizine in the treatment of moderate to severe SAR.

METHODS

This multicenter, randomized, double-blind, parallel-group, 2-week comparative study was conducted during the 2004 fall allergy season in patients with moderate to severe SAR. After a 1-week placebo lead-in period, patients were randomized to receive azelastine nasal spray 2 sprays per nostril twice daily plus placebo tablets or cetirizine 10-mg tablets once daily plus a placebo saline nasal spray for the 2-week double-blind treatment period. The primary efficacy variables were (1) change from baseline to day 14 in the 12-hour reflective total nasal symptom score (TNSS), which combines scores for rhinorrhea, sneezing, itchy nose, and nasal congestion, and (2) onset of action, based on the instantaneous TNSS over 4 hours after the first dose of study drug. During the double-blind treatment period, patients recorded their symptom scores on diary cards twice daily (morning and evening). Patients aged > or =18 years also completed the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) at baseline and on day 14.

RESULTS

Three hundred seven patients were randomized to treatment, and 299 completed 2 weeks of study treatment. The age of the population ranged from 12 to 74 years (mean, 35 years), 62.9% were female, and 69.6% were white. Over 2 weeks of treatment, both groups had significant improvements in the TNSS compared with baseline (P < 0.001). The overall change in TNSS was significantly greater with azelastine nasal spray compared with cetirizine (29.3% vs 23.0% improvement, respectively; P = 0.015). In terms of onset of action, azelastine nasal spray significantly improved the instantaneous TNSS compared with cetirizine at 60 and 240 minutes after the initial dose (both, P = 0.040). Scores on each domain of the RQLQ were significantly improved in both groups compared with baseline (P < 0.001); the overall RQLQ score was significantly improved with azelastine nasal spray compared with cetirizine (P = 0.049). Both treatments were well tolerated.

CONCLUSION

In this 2-week study in patients with moderate to severe SAR, azelastine nasal spray was well tolerated and produced significantly greater improvements in TNSS and total RQLQ score compared with cetirizine.

The efficacy of short-term administration of 3 antihistamines vs placebo under natural exposure to Japanese cedar pollen

BACKGROUND

Japanese cedar pollinosis, a common disease with morbidity of approximately 20% in the Japanese population, is characterized by subjectively irritating symptoms during an annual 3-month period.

OBJECTIVE

To investigate the effectiveness of cetirizine hydrochloride, loratadine, and fexofenadine hydrochloride in reducing pollinosis symptoms induced while walking in a park during the pollen season.

METHODS

A randomized, double-masked, placebo-controlled trial was conducted in 113 individuals with Japanese cedar pollinosis during 2 days in March 2003 in Osaka Expo Park, Osaka, Japan. Participants (aged 20-57 years) were divided into 4 groups according to treatment assignment: cetirizine hydrochloride, 10 mg/d; fexofenadine hydrochloride, 120 mg/d; loratadine, 10 mg/d; and placebo (lactose), twice daily. Symptoms were recorded hourly during the study. Furthermore, all the patients completed the Japanese version of the Rhinoconjunctivitis Quality of Life Questionnaire before and after the trial.

RESULTS

Self-evaluated symptom scores in all 3 active treatment groups showed significant improvements compared with the placebo group. Furthermore, the cetirizine group showed significant improvement in the domains of frequency of nose blowing and nasal obstruction compared with placebo. In addition, improvement in Japanese Rhinoconjunctivitis Quality of Life Questionnaire scores was higher in the cetirizine group than in the loratadine and placebo groups.

CONCLUSION

Cetirizine seems to be more effective than fexofenadine and loratadine at reducing subjective symptoms in this study population.

Pediatric Allergic Rhinitis: Factors Affecting Treatment Choice

Allergic rhinitis is the most prevalent chronic allergic disease in children. Although it is not life-threatening, it can have a significantly detrimental effect on a child's quality of life, and it may exacerbate a number of common comorbidities, including asthma and sinusitis. The Allergic Rhinitis and its Impact on Asthma guidelines, an evidence-based algorithm for the treatment of allergic rhinitis, advocate the use of antihistamines for the treatment of the broad spectrum of the disease. However, first-generation antihistamines are associated with a number of adverse events, including central nervous system impairment and anticholinergic and cardiovascular effects. Moreover, these agents have not been rigorously tested in the pediatric population. Nevertheless, first-generation antihistamines remain the most frequently prescribed agents in this class of drugs. This is despite the fact that the second-generation antihistamines are largely free of the undesirable side effects associated with their predecessors and the fact that they have been shown to be effective in relieving allergic rhinitis symptoms in children in a number of large-scale clinical trials. Therefore, when selecting an antihistamine for a child, it would be prudent to consider the full range of antihistamines and to base the selection of a particular drug on its efficacy, onset and duration of action, and safety profile.

Similar rapid onset of action and magnitude of effect of fexofenadine and cetirizine as assessed by inhibition of histamine-induced wheal-and-flare reaction

BACKGROUND

Histamine-induced wheal-and-flare studies are useful, objective tests for determining differences in the peripheral H1-receptor blockade activities of antihistamines.

OBJECTIVE

To evaluate the time of occurrence of 95% inhibition of histamine-induced wheal and flare after administration of fexofenadine hydrochloride, 180 mg, or cetirizine, 10 mg.

METHODS

Forty-two volunteers (aged 18-60 years) were included in a randomized, double-blind, crossover study. Skin prick tests were undertaken using histamine (100 mg/mL) before treatment and 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 hours after treatment. Wheal and flare areas were evaluated, and the time to occurrence of 95% inhibition and the frequency of subjects exhibiting 95% inhibition before median time to 95% inhibition were calculated.

RESULTS

Mean +/- SD time to 95% wheal inhibition was 2.46 +/- 0.71 hours with fexofenadine and 2.55 +/- 0.57 hours with cetirizine. The estimated mean difference between fexofenadine and cetirizine (-7 minutes in favor of fexofenadine; 2-sided 95% confidence interval, -21 to +7 minutes) was not statistically significant (P = .34). For wheal, 29% of subjects receiving fexofenadine and 24% receiving cetirizine achieved 95% inhibition before the median time of inhibition (2.5 hours). An exact permutation test yielded a P = .37. For flare, 26% of subjects receiving fexofenadine and 10% receiving cetirizine achieved 95% inhibition before the median time of inhibition (3 hours; P = .12 by exact permutation test).

CONCLUSIONS

Fexofenadine and cetirizine have comparable onset of action times and similar frequencies of inhibition, as evaluated by the occurrence of 95% inhibition of histamine-induced wheal and flare.

Second-Generation Antihistamines

Antihistamines are useful medications for the treatment of a variety of allergic disorders. Second-generation antihistamines avidly and selectively bind to peripheral histamine H1 receptors and, consequently, provide gratifying relief of histamine-mediated symptoms in a majority of atopic patients. This tight receptor specificity additionally leads to few effects on other neuronal or hormonal systems, with the result that adverse effects associated with these medications, with the exception of noticeable sedation in about 10% of cetirizine-treated patients, resemble those of placebo overall. Similarly, serious adverse drug reactions and interactions are uncommon with these medicines. Therapeutic interchange to one of the available second-generation antihistamines is a reasonable approach to limiting an institutional formulary, and adoption of such a policy has proven capable of creating substantial cost savings. Differences in overall efficacy and safety between available second-generation antihistamines, when administered in equivalent dosages, are not large. However, among the antihistamines presently available, fexofenadine may offer the best overall balance of effectiveness and safety, and this agent is an appropriate selection for initial or switch therapy for most patients with mild or moderate allergic symptoms. Cetirizine is the most potent antihistamine available and has been subjected to more clinical study than any other. This agent is appropriate for patients proven unresponsive to other antihistamines and for those with the most severe symptoms who might benefit from antihistamine treatment of the highest potency that can be dose-titrated up to maximal intensity.

Cetirizine: a review of its use in allergic disorders

Cetirizine is a selective, second-generation histamine H1 receptor antagonist, with a rapid onset, a long duration of activity and low potential for interaction with drugs metabolised by the hepatic cytochrome P450 system. Cetirizine was generally more effective than other H1 receptor antagonists at inhibiting histamine-induced wheal and flare responses. Cetirizine is an effective and well tolerated agent for the treatment of symptoms of seasonal allergic rhinitis (SAR), perennial allergic rhinitis (PAR) and chronic idiopathic urticaria (CIU) in adult, adolescent and paediatric patients. In adults with these allergic disorders, cetirizine was as effective as conventional dosages of ebastine (SAR, PAR, CIU), fexofenadine (SAR), loratadine (SAR, CIU) or mizolastine (SAR). This agent was significantly more effective, and with a more rapid onset of action, than loratadine in 2-day studies in environmental exposure units (SAR). In paediatric patients, cetirizine was as at least as effective as chlorphenamine (chlorpheniramine) [SAR], loratadine (SAR, PAR) and oxatomide (CIU) in the short term, and more effective than oxatomide and ketotifen (PAR) in the long term. Cetirizine was effective in reducing symptoms of allergic asthma in adults and reduced the relative risk of developing asthma in infants with atopic dermatitis sensitised to grass pollen or house dust mite allergens. It had a corticosteroid-sparing effect in infants with severe atopic dermatitis and was effective in ameliorating reactions to mosquito bites in adults. Cetirizine was well tolerated in adults, adolescents and paediatric patients with allergic disorders. In adult, adolescent and paediatric patients aged 2-11 years, the incidence of somnolence with cetirizine was dose related and was generally similar to that with other second-generation H1 receptor antagonists. Although, its sedative effect was greater than that of fexofenadine in some clinical trials and that of loratadine or fexofenadine in a postmarketing surveillance study. In infants aged 6-24 months, the tolerability profile of cetirizine was similar to that of placebo. Cetirizine did not have any adverse effects on cognitive function in adults, or cognitive function, behaviour or achievement of psychomotor milestones in paediatric patients. Cetirizine was not associated with cardiotoxicity.

CONCLUSION

Cetirizine is well established in the treatment of symptoms of SAR, PAR or CIU. It demonstrated a corticosteroid-sparing effect and reduced the relative risk of developing asthma in sensitised infants with atopic dermatitis. Cetirizine was effective in the treatment of allergic cough and mosquito bites; however, its precise role in these indications has yet to be clearly established. On the basis of its favourable efficacy and tolerability profile and rapid onset of action, cetirizine provides an important option for the treatment of a wide range of allergic disorders.

Review of cetirizine hydrochloride for the treatment of allergic disorders

Cetirizine hydrochloride is an orally-active and selective histamine (H(1))-receptor antagonist. It is a second-generation antihistamine and a human metabolite of hydroxyzine. Therefore, its principal effects are mediated via selective inhibition of peripheral H(1) receptors. The antihistaminic activity of cetirizine has been documented in a variety of animal and human models. In vivo and ex vivo animal models have shown negligible anticholinergic and antiserotonergic activity. In clinical studies, however, dry mouth has been seen more commonly with cetirizine than with placebo. In vitro receptor binding studies have shown no measurable affinity for receptors other than H(1) receptors. Auto-radiographical studies with radiolabelled cetirizine in the rat have shown negligible penetration into the brain. Ex vivo experiments in the mouse have shown that systemically administered cetirizine does not significantly occupy cerebral H(1) receptors. Impairment of CNS function is comparable to other low-sedating antihistamines at the recommended dose of 10 mg/day for adults. It has anti-inflammatory properties that may play a role in asthma management. It does not interact with concomitantly administered medications, it has no cardiac adverse effects, and it does not appear to be associated with teratogenicity. Cetirizine is predominantly eliminated by the kidneys with a mean elimination half-life is 8.3 h. It is rapidly absorbed, and significant clinical inhibition of a wheal and flare response occurs in infants, children and adults within 20 min of a single oral dose and persists for 24 h. No tolerance to the wheal and flare response occurs even after 1 month of daily treatment. The clinical efficacy of cetirizine for allergic respiratory diseases has been established in numerous trials. There is evidence that cetirizine improves symptoms of urticaria. Concomitant use of cetirizine also decreases the duration and amount of topical anti-inflammatory preparations needed for the treatment of atopic dermatitis. Interestingly, several clinical studies suggest that cetirizine may be useful in the treatment and prevention of mild asthma.

Comparative clinical efficacy, onset and duration of action of levocetirizine and desloratadine for symptoms of seasonal allergic rhinitis in subjects evaluated in the Environmental Exposure Unit (EEU)

The Environmental Exposure Unit, an indoor pollen challenge system to test anti-allergic medications, was used to compare the onset and duration of action and the efficacy of levocetirizine and desloratadine, two recently developed H1-antagonists. In this double-blind, placebo-controlled, parallel-group study, qualified subjects were randomised to once-daily levocetirizine 5 mg (n = 141), desloratadine 5 mg (n = 140) or placebo (n = 92) and exposed to ragweed pollen on two consecutive days (7 h and 6 h). Symptoms were self-rated every 30 min. On both days, levocetirizine produced a greater improvement in the major symptom complex score (primary efficacy variable) than desloratadine (p = 0.015); both were better than placebo (p < 0.001). Levocetirizine acted earlier (1 h vs. 3 h) and produced greater symptom relief at 24 h than desloratadine (p = 0.003). Levocetirizine also alleviated nasal obstruction better than desloratadine (p = 0.007) on day 1; and better than placebo (p = 0.014) after the second dose on day 2, which was not observed with desloratadine. Levocetirizine and desloratadine were safe and well tolerated.

Comparison of the effects of desloratadine 5-mg daily and placebo on nasal airflow and seasonal allergic rhinitis symptoms induced by grass pollen exposure

BACKGROUND

Nasal congestion is a chronic symptom of seasonal allergic rhinitis (SAR) that is often difficult to treat with antihistamines. Desloratadine, a new, potent, H1-receptor antagonist has been shown to decrease nasal congestion in clinical trials and to maintain nasal airflow in response to grass pollen exposure. We compared the effects of desloratadine 5 mg and placebo on nasal airflow, nasal secretion weights and SAR symptoms, including nasal congestion, in patients exposed to grass pollen in an environmental exposure unit.

METHODS

Forty-six grass pollen allergic SAR patients received desloratadine or placebo for 7 days, followed by a 10-day washout, and then crossed over to the other treatment for 7 days. A 6-h allergen exposure was performed at the end of each treatment period.

RESULTS

Desloratadine was significantly superior to placebo in maintaining nasal airflow (P <or= 0.014) and lessening the increase in nasal secretion weights (P < 0.001) throughout allergen exposure. SAR symptom scores, including nasal congestion, were significantly less with desloratadine than placebo (P <or= 0.001). Desloratadine was well tolerated.

CONCLUSIONS

This study confirms that, compared with placebo, desloratadine can maintain nasal airflow and reduce nasal secretion weights and the severity of SAR symptoms, including nasal congestion, in SAR patients exposed to grass pollen allergen.

Comparative pharmacology of H1 antihistamines: clinical relevance

H1 antihistamines have similar efficacy in the treatment of allergic disorders; however, they differ in terms of their chemical structure, clinical pharmacology, and safety. This review focuses on the clinical pharmacology (pharmacokinetics and pharmacodynamics) of the newer oral H1 antihistamines (acrivastine, cetirizine, desloratadine, ebastine, fexofenadine, levocetirizine, loratadine, and mizolastine). Understanding the pharmacokinetics and pharmacodynamics of these H1 antihistamines provides an objective basis for selection of appropriate dosages and dose intervals. Pharmacokinetic and pharmacodynamic studies provide a rationale for the modified dosage regimens that may be required in special populations, such as the very young, the elderly, those with hepatic or renal dysfunction, or those taking other medications concurrently. Many H1 antihistamines are currently available for use. Clinical pharmacology studies help physicians to select the best H1 antihistamines for their patients.