The effect of cetirizine on early allergic response

Effects of Cetirizine on Substance P Release in Patients with Perennial Allergic Rhinitis

To evaluate the effect of cetirizine hydrochloride on substance P release in allergic rhinitis, we performed a single-blind placebo-controlled study of 14 patients with perennial allergic rhinitis (7 treated with cetirizine and 7 with placebo). After an initial nasal allergen challenge with lavages, the subjects received treatment with placebo or cetirizine hydrochloride (10 mg by mouth daily) for 1 week, followed by the second nasal allergen challenge with lavages. The levels of albumin, histamine, and substance P in nasal lavages before and after allergen challenge were quantified by enzyme-linked immunosorbent assay. Pretreatment of subjects with cetirizine reduced the level of substance P induced by antigen challenge, but did not significantly reduce levels of histamine. These results suggest that cetirizine may reduce nasal neurogenic inflammation by modulating the release of substance P in allergic rhinitis.

New topics in bradykinin research

Bradykinin has been implicated to contribute to allergic inflammation and the pathogenesis of allergic conditions. It binds to endothelial B(1) and B(2) receptors and exerts potent pharmacological and physiological effects, notably, decreased blood pressure, increased vascular permeability and the promotion of classical symptoms of inflammation such as vasodilation, hyperthermia, oedema and pain. Towards potential clinical benefit, bradykinin has also been shown to exert potent antithrombogenic, antiproliferative and antifibrogenic effects. The development of pharmacologically active substances, such as bradykinin receptor blockers, opens up new therapeutic options that require further research into bradykinin. This review presents current understanding surrounding the role of bradykinin in nonallergic angioedema and other conditions seen by allergists and emergency physicians, and its potential role as a therapeutic target.

Reproducibility of nasal allergen challenge in evaluating the efficacy of intranasal corticosteroid treatment

BACKGROUND

Although nasal challenge with allergen has often been used to evaluate the efficacy of therapeutic modalities used for the treatment of allergic rhinitis, the reproducibility of this model in quantitatively evaluating efficacy has not been rigorously examined.

OBJECTIVE

To examine the reproducibility of the suppressive effects of an intranasal corticosteroid on the clinical and biochemical outcomes of a nasal allergen challenge during two identical treatment periods using the same subjects.

METHODS

In a single-blind study, 25 seasonal allergic subjects with positive skin tests to grass or ragweed were studied outside of their pollen season. Subjects underwent a baseline, three-dose allergen challenge. Beginning 1 week later, subjects received two 7-day courses of intranasal beclomethasone (168 microg b.i.d.) separated by a 1-month washout period. Nasal challenges with allergen were performed after each treatment period. The nasal allergic response was evaluated by counting sneezes, recording symptom scores and measuring levels of albumin (an index of vascular permeability), lysozyme (an index of serous glandular secretion) and kinins (proinflammatory peptides) in recovered nasal lavages.

RESULTS

Compared with the baseline challenge, each course of beclomethasone significantly reduced sneezing, symptom scores, albumin and kinins, but not lysozyme. Reproducibility analysis of the net changes from diluent challenge in the two beclomethasone treatment periods, showed the following intraclass correlation coefficients: sneezing (0.92), lysozyme (0.82), symptom scores (0.72), albumin (0.64) and kinins (0.28).

CONCLUSION

We conclude that the nasal challenge model is a reproducible method to evaluate the efficacy of anti-allergic medications. For nasal corticosteroid trials, sneezing, symptom scores and albumin levels are recommended as the most reproducibly suppressive outcome measures.

The effects of the nasal antihistamines olopatadine and azelastine in nasal allergen provocation

BACKGROUND

Olopatadine, an antihistamine used in allergic conjunctivitis, is under development as a nasal preparation for the treatment of allergic rhinitis.

OBJECTIVES

To evaluate the efficacy of olopatadine in suppressing symptoms and biomarkers of the immediate reaction induced by nasal allergen provocation and to compare olopatadine with azelastine in the same model.

METHODS

The study was approved by the Johns Hopkins University institutional review board, and all subjects gave written consent. We studied 20 asymptomatic subjects with seasonal allergic rhinitis. The study had 2 randomized, double-blind, placebo-controlled, crossover phases that evaluated 2 concentrations of olopatadine, 0.1% and 0.2%. In a third exploratory phase, olopatadine, 0.1%, was compared with topical azelastine, 0.1%, in a patient-masked design. Efficacy variables were the allergen-induced sneezes, other clinical symptoms, and the levels of histamine, tryptase, albumin, lysozyme, and cysteinyl-leukotrienes (third study only) in nasal lavage fluids.

RESULTS

Both concentrations of olopatadine produced significant inhibition of all nasal symptoms, compared with placebo. Olopatadine, 0.1%, inhibited lysozyme levels, but olopatadine, 0.2%, inhibited histamine, albumin, and lysozyme. The effects of olopatadine, 0.1%, were comparable to those of azelastine, 0.1%.

CONCLUSIONS

Olopatadine, at 0.1% and 0.2% concentrations, was effective in suppressing allergen-induced nasal symptoms. At 0.2%, olopatadine provided evidence suggestive of inhibition of mast cell degranulation.

Clinical efficacy and pharmacokinetic profiles of intranasal and oral cetirizine in a repeated allergen challenge model of allergic rhinitis

BACKGROUND

Intranasal and oral antihistamines are effective in treating allergic rhinitis. Studies comparing these routes of administration of an antihistamine regarding efficacy and pharmacokinetic profile are lacking.

OBJECTIVE

To compare topical and oral routes of administration of cetirizine regarding efficacy, plasma exudation, and systemic drug levels in a repeated allergen challenge model of allergic rhinitis.

METHODS

Oral cetirizine dihydrochloride, 10 mg once daily, and topical cetirizine dinitrate in a dose corresponding to 4.4 mg of the dihydrochloride salt twice daily were given to grass pollen-sensitive individuals for 12 days in a double-blind, placebo-controlled, crossover design. Timothy grass pollen allergen challenges were given once daily for 7 days using a nasal spray device. Nasal symptoms and peak inspiratory flow were recorded in the morning, 10 minutes after allergen challenge, and in the evening. The pharmacokinetics of the treatments was monitored in 8 patients. The remaining 28 patients were challenged topically with histamine 12 and 24 hours after the final topical and oral cetirizine doses, respectively. Nasal lavage levels of alpha2-macroglobulin were determined to evaluate histamine-induced mucosal plasma exudation.

RESULTS

During the last 3 days of the repeated allergen challenge model, chronic symptoms were established. Both treatments reduced symptoms 10 minutes after allergen challenge (P < .001 vs placebo). Neither treatment reduced morning and evening symptoms or nasal peak inspiratory flow. Topical, but not oral, cetirizine reduced histamine-induced plasma exudation (P < .01 vs placebo) when systemic drug levels were similar in the 2 treatment regimens.

CONCLUSIONS

Topical and oral cetirizine reduced acute nasal symptoms produced by allergen challenges in patients with established chronic symptoms. There were also antihistaminic effects of topical cetirizine not related to systemic drug levels.

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.

Effects of fexofenadine on the early response to nasal allergen challenge

BACKGROUND

Previous studies using nasal allergen challenge models have shown that terfenadine, an H1 antihistamine, inhibits histamine release during the early response to allergen provocation. Fexofenadine, the active metabolite of terfenadine, has strong H1-antihistaminic activity and no cardiac effects. Clinical studies have documented the efficacy of fexofenadine in the treatment of allergic rhinitis.

OBJECTIVE

To determine whether fexofenadine, like terfenadine, inhibits histamine and tryptase release during the early allergic response.

METHODS

Randomized, double blind, placebo-controlled, two-way crossover study in 20 subjects with seasonal allergic rhinitis, out of their allergy season (median age 27.5 years, 13 males and 7 females). Subjects were medicated with either placebo or fexofenadine 180 mg orally daily for 1 week followed by nasal challenge with allergen. After each challenge, sneezes and nasal symptoms were recorded, and a nasal lavage was obtained for the assay of albumin, an indicator of vascular permeability, and histamine and tryptase, indicators of mast cell degranulation.

RESULTS

When patients were on placebo, allergen challenges led to significant increases in all measured parameters compared with the sham challenges with diluent. Treatment with fexofenadine resulted in inhibition of allergen-induced symptoms and increased vascular permeability, but not the release of histamine and tryptase.

CONCLUSION

Fexofenadine is an effective H1 antihistamine, but in contrast to its parent compound, terfenadine, it does not affect the release of the mast cell mediators histamine and tryptase.

Evaluation of cytokines in nasal secretions after nasal antigen challenge: lack of influence of antihistamines

BACKGROUND

Previous studies of inflammation in allergic rhinitis using nasal irrication have been unsatisfactory because of 1) poor reproducibility; 2) the tendency of irrigation to overdilute mediators; and 3) the failure of this technique to evaluate interstitial concentrations of relevant mediators. For this study we used filter paper as a matrix to collect nasal secretions in patients undergoing nasal antigen challenge.

OBJECTIVE

To evaluate inflammatory mediators of allergen-induced rhinitis during a clinical trial of fexofenadine.

METHODS

Subjects evaluated at a referral medical center were placed on traditional dosing of fexofenadine at 60 mg, twice daily, or placebo in a double-blind, crossover fashion for 1 week before the nasal challenge. Nasal challenge was performed with nasal insufflation of either 1,000 AU timothy or 0.1 mL ragweed (1:100 wt/vol) extract outside the pollen season. Nasal secretions were collected at baseline and then at 2, 4, and 6 hours after nasal challenge. Secretions were evaluated for expression of the cellular adhesion molecule-1, tumor necrosis factor (TNF)-alpha, interleukin (IL)-4, IL-10, macrophage inflammatory protein (MIP)-1alpha, and granulocyte-macrophage colony-stimulating factor (GM-CSF) using commercially available enzyme-linked immunoadsorbent assay kits. Patients' symptom scores were evaluated during the nasal challenge.

RESULTS

Significantly (P < 0.05) increased peak levels of TNF-alpha, IL-4, IL-10, and MIP-1alpha were detected after antigen challenge as compared with baseline levels. There was a nonsignificant trend toward an increase in GM-CSF after antigen challenge (P = 0.07). There was no difference in the peak levels of TNF-alpha, IL-4, IL-10, MIP-1alpha, or GM-CSF measured when patients were on fexofenadine versus placebo. Finally, there were no significant differences in patients' symptom scores during antigen challenge when subjects were on fexofenadine versus placebo.

CONCLUSIONS

Collection of nasal secretions using a filter paper matrix provides a reproducible model for accurately detecting and evaluating changes in cytokine levels after nasal challenge. Cytokine levels tend to peak 3 to 4 hours after antigen challenge. Standard doses of fexofenadine do not seem to have a mitigating effect on the production of these cytokines. Symptoms of allergic rhinitis using this type of antigen challenge did not differ from treatment with fexofenadine versus placebo.

Antiallergic effects of H1-receptor antagonists

The primary mechanism of antihistamine action in the treatment of allergic diseases is believed to be competitive antagonism of histamine binding to cellular receptors (specifically, the H1-receptors), which are present on nerve endings, smooth muscles, and glandular cells. This notion is supported by the fact that structurally unrelated drugs antagonize the H1-receptor and provide clinical benefit. However, H1-receptor antagonism may not be their sole mechanism of action in treating allergic rhinitis. On the basis of in vitro and animal experiments, drugs classified as H1-receptor antagonists have long been recognized to have additional pharmacological properties. Most first-generation H1-antihistamines have anticholinergic, sedative, local anaesthetic, and anti-5-HT effects, which might favourably affect the symptoms of the allergic response but also contribute to side-effects. These additional properties are not uniformly distributed among drugs classified as H1-receptor antagonists. Azatadine, for example, inhibits in vitro IgE-mediated histamine and leukotriene (LT) release from mast cells and basophils. In human challenge models, terfenadine, azatadine, and loratadine reduce IgE-mediated histamine release. Cetirizine reduces eosinophilic infiltration at the site of antigen challenge in the skin, but not the nose. In a nasal antigen challenge model, cetirizine pretreatment did not affect the levels of histamine and prostaglandin D2 recovered in postchallenge lavages, whereas the levels of albumin, N-tosyl-L-arginine methyl ester (TAME) esterase activity, and LTs were reduced. Terfenadine, cetirizine, and loratadine blocked allergen-induced hyperresponsiveness to methacholine. In view of the complexity of the pathophysiology of allergy, a number of H1 antagonists with additional properties are currently under development for allergic diseases. Mizolastine, a new H1-receptor antagonist, has been shown to have additional actions that should help reduce the allergic response. In animal models, mizolastine inhibits antigen-induced eosinophil infiltration into mouse skin and into the nasal cavity of guinea-pigs. Mizolastine also significantly inhibits antigen-induced neutrophil infiltration into the bronchoalveolar lavage fluids of guinea-pigs. In addition, it inhibits arachidonic acid-induced paw oedema in rats without affecting carrageenin-induced rat paw oedema, suggesting an effect on LT generation. In man, mizolastine inhibits early and late antigen-induced soluble intercellular adhesion molecule 1 (ICAM-1) levels in skin blisters. It also inhibits anaphylactic release of histamine from rodent mast cells, LTC4 and LTB4 release from mouse bone-marrow-derived mast cells, LTC4 release from rat intestinal mast cells, and 5-lipoxygenase activity of polymorphonuclear neutrophils of guinea-pig intestines and rat basophilic leukaemia cells. It is clear that a number of H1-antihistamines have multiple effects on the allergic inflammatory response. It is equally clear that these antiallergic effects are not uniformly shared among all drugs of this class. The assessment of the clinical significance of these results and research regarding the parts of the molecules responsible for these activities are underway.

A comparison of the anti-inflammatory properties of intranasal corticosteroids and antihistamines in allergic rhinitis

Allergic rhinitis manifests itself clinically due to the local release of mediators from activated cells within the nasal mucosa. Treatment strategies aim either to reduce the effects of these mediators on the sensory neural and vascular end organs, or to reduce the tissue accumulation of the activated cells that generate them. Corticosteroids intervene at a number of steps in the inflammatory pathway, and, by reducing the release of cytokines and chemokines, inhibit cell recruitment and activation. These effects are evident both in vivo and in vitro. While antihistamines also have some anti-inflammatory effects in vitro, these require higher concentrations than with corticosteroids and are not consistently reproduced in vivo. In addition, although antihistamines and corticosteroids might appear to have complementary mechanisms of action, clinical trials suggest that their co-administration does not confer any additional long-term benefits compared with that achieved with corticosteroids alone. Topical corticosteroids are therefore the preferred anti-inflammatory therapy for persistent allergic rhinitis.

Allergic inflammation in upper and lower airways

OBJECTIVE

The primary reason for this review is to discuss the relationship between upper and lower airways at various levels with the emphasis on common pathophysiologic mechanisms, and how treatment of the upper airways will benefit the lower airways.

DATA SOURCES

The main source of information is derived from original articles and books, with an extensive bibliography included.

STUDY SELECTION

Studies were derived almost exclusively from articles and reviews in peer-reviewed journals.

RESULTS

The prevalence of rhinitis and asthma are both increasing. Common to both the upper and lower airways are the triggers, many of the inflammatory cells and mediators, and the treatment modalities. By contrast, there are organ-specific differences in the reaction to various stimuli in the nose or lung, with each organ manifesting its own vocabulary of response.

CONCLUSIONS

There are meaningful relationships between upper and lower airways at various levels of our understanding. Differential responses to medications help us better understand pathogenic mechanisms in rhinitis and asthma. Further, treatment of the upper airways provides additional benefit to the lower airways.

Histamine H1 receptor and reactivity of the nasal mucosa in sensitized guinea pigs

OBJECTIVE

Nasal Hypersensitivity to histamine is higher in allergic patients than that in normal control, suggesting that affinity and/or density of H1 receptors in nasal mucosa may be increased in patients with allergic rhinitis. The purpose in this study is to examine the correlation between the hyperresponsiveness and number of histamine H1 receptors in guinea pig nasal mucosa.

METHODS

Guinea pigs were sensitized by DNP-Ascaris antigen. To block histamine H1 receptors, ketotifen was used and the number of receptors was counted by receptor binding assay technique. These data were compared with nasal airway volume (VOL) assessed by acoustic rhinometry of the same animals to know whether the number of H1 receptors is correlated to the nasal responsiveness to the antigen, or not. Eighty animals were divided into five groups which are composed of nonsensitized and sensitized group pretreated with saline, 0.1, 1.0 and 10 mg/kg of ketotifen, respectively.

RESULTS

The number of H1 receptors (Bmax) was significantly increased in sensitized group compared with that in control. It decreased dose dependently by pretreatment of ketotifen. The percent change of VOL showed - 31.1 +/- 4.1% at 10 min and - 42.9 +/- 4.1% at 30 min after antigen challenge in sensitized animals. This was dose dependently inhibited by ketotifen. There was a highly inverse correlation between VOL and Bmax (r = -0.708, P< 0.0001).

CONCLUSION

These results suggest that sensitization increases the number of histamine H1 receptor, and that increased number of H1 receptor in nasal mucosa in sensitized guinea pigs may be one of the causes of nasal hyperresponsiveness to antigen.

Assessment of antihistamine efficacy and potency

H1 antihistamines are widely used in the treatment of conditions such as seasonal and perennial allergic rhinitis, urticaria and angioedema, as well as being an adjunct therapy for anaphylaxis. The development of new compounds within this class of pharmacological agents is based on preclinical and clinical assessments prior to registration. Preclinical assessment of novel compounds has been advanced both by the definition of the molecular structure of the H1 receptor and by high throughput screening, which allows the definition of potent and selective candidate compounds. The elimination, in subsequent evaluations, of those compounds with potential for central nervous system and cardiotoxic effects and those with inappropriate pharmacokinetics restricts the subsequent toxicological and clinical evaluation of novel H1 antihistamines. Clinical evaluation is based initially on human volunteer studies to define pharmacodynamic, pharmacokinetic and safety parameters. Local challenge models such as in the skin or nose for oral therapy or nose and conjunctiva for topical drug development allow definition of potential dose for administration, speed of onset of activity and duration of effect, both in comparison to placebo and to reference compounds. While a range of laboratory allergen challenge models, pollen chamber challenge studies and acute 'day in the park' study designs have been used in the early clinical evaluation of H1 antihistaminic activity, ultimately it is the efficacy of novel compounds in naturally occurring disease that is of importance. The assessment of the magnitude and profile of clinical disease improvement in specific disease areas is thus the crucial evaluation. The appropriate selection and characterization of patients, the optimization of the trial design, dependent upon the nature of the disease, and the appropriate selection of endpoints for analysis are thus critical considerations, as well as evaluation of appropriate safety criteria.

Beyond the histamine receptor: effect of antihistamines on mast cells

Many antihistamines exhibit inhibition of mediator release from mast cells and basophils, in in vitro studies in addition to H1 antagonism. The underlying mechanism is unclear but is unrelated to H1-receptor antagonism. Clinical studies of antihistamins in antigen challenge and seasonal allergy demonstrate reduction of mast cell mediators in nasal lavage. It is not known what mechanism(s) underly these observations, although the concentrations required in in vitro studies suggests that a direct effect on mast cells is unlikely. Furthermore, the therapeutic contribution of this effect is difficult to assess because of concomitant clinically significant H1 antagonism. This and other potential anti-allergic effects may enhance the therapeutic benefit of antihistamines and long-term studies are underway to explore this possibility.

Histamine and tryptase in nasal lavage fluid after allergen challenge: effect of 1 week of pretreatment with intranasal azelastine or systemic cetirizine

BACKGROUND

Antihistamines (H1-receptor antagonists) act by competitive antagonism of histamine at H1-receptors. In addition, high concentrations of some antihistamines inhibit allergen-induced histamine release from mast cells in vitro.

OBJECTIVE

The purpose of this study was to determine the effect of intranasal azelastine or systemic cetirizine (both potent antihistamines) on the allergen-induced release of mast-cell mediators from the human nasal mucosa in vivo.

METHODS

Patients allergic to birch pollen (n = 11) and control subjects not allergic to birch pollen (n = 5) were included in a randomized, double-blind, placebo-controlled, 3-way crossover study outside the pollen season. Each subject was treated with azelastine nasal spray 0.14 mg per nostril twice daily, cetirizine tablets 10 mg every day, or placebo for 1 week using a double-dummy design. At the end of each treatment period, nasal allergen challenges were performed, and the number of sneezes were counted. In addition, nasal lavage fluid was collected, and the levels of mast-cell mediators (histamine and tryptase) were measured.

RESULTS

The allergen challenge of patients allergic to pollen produced sneezing and a significant increase in the levels of histamine and tryptase. The challenge of subjects not allergic to pollen produced no such response. Azelastine and cetirizine significantly reduced allergen-induced sneezing and the associated increase in histamine and tryptase levels. No significant differences were found between the azelastine and cetirizine treatments.

CONCLUSION

Pretreatment with azelastine or cetirizine inhibits the allergen-induced release of mast-cell mediators from the human nasal mucosa. Our results are consistent with the hypothesis that both antihistamines reduce mediator release from nasal mucosa mast cells in vivo. However, further studies are necessary to test this hypothesis.

Pros and cons of the use of antihistamines in managing allergic rhinitis

Histamine H1 -receptor antagonists are generally considered first-line therapy for the management of allergic rhinitis. Other than histamine antagonism, several of the second-generation antihistamines have also shown inhibitory effects on chemical mediators of inflammation such as leukotrienes, prostaglandins, and kinins. This article reviews the pharmacology, clinical use, and side effect profiles of the commonly used H1 -receptor antagonists.

Relationship between histamine and physiological changes during the early response to nasal antigen provocation

To investigate the temporal relationships of mediator release and physiological changes during the early response to allergen, we challenged allergic individuals intranasally with antigen and followed their responses. This was done by using small filter paper disks to challenge one nostril and collect secretions from both the challenged and the contralateral nostril, thus enabling us to evaluate the nasonasal reflex. There was a significant increase in sneezing after allergen challenge that peaked within 2 min and returned to baseline. The weights of nasal secretions as well as nasal symptoms increased immediately and remained significantly elevated for 20 min in both nostrils. Nasal airway resistance increased slowly, reaching its peak at approximately 6 min after challenge on the ipsilateral side, but it did not change on the contralateral side. Histamine levels peaked 30 s after removal of the allergen disk on the side of challenge, whereas albumin levels peaked after those of histamine. Lactoferrin paralleled the increase in secretion weights and occurred in both nostrils. Increasing doses of antigen produced dose-dependent increases in all parameters, whereas control challenges produced no response. These studies describe a human model for the evaluation of the allergic response that is capable of simultaneously measuring mediator release and the physiological response, including the nasonasal reflex. This model should prove useful in studying the mechanism of allergic rhinitis in humans.

Effects of topical budesonide and levocabastine on nasal symptoms and plasma exudation responses in seasonal allergic rhinitis

This study compares the effects of two topical nasal treatments for allergic rhinitis, budesonide and levocabastine, on symptom development during seasonal pollen exposure. Additionally, the protective effects of drug treatments on allergen-challenge-induced responses (symptoms and microvascular exudation of plasma) are examined late into the pollen season. Forty-four patients with seasonal allergic rhinitis to birch pollen participated in this single-blind, randomized, and placebo-controlled study. Topical nasal treatment with either levocabastine (200 microg b.i.d.; n = 16), budesonide (200 microg b.i.d.; n = 16), or placebo (n = 12) was instituted before the start of the pollen season and continued for 5 weeks until the end of the birch pollen season. The participants kept diaries for scores of nasal and ocular symptoms. Nasal allergen challenges with increasing doses of a birch pollen extract (10[2], 10[3], and 10[4] SQ-U) were carried out both before, when patients were asymptomatic and without treatment, and late into the pollen season. A nasal lavage followed each challenge, and the lavage fluid levels of albumin were measured as an index of the acute inflammatory response of the allergic mucosa. The birch pollen season was rather mild, producing only small increases in nasal symptoms. Budesonide treatment reduced the total nasal symptoms compared to placebo (P<0.01) and to levocabastine (P<0.05), while levocabastine treatment did not differ significantly from placebo. Ocular symptoms and use of rescue medication did not differ between placebo and the active treatments. At the end of the pollen season, both treatments reduced allergen-challenge-induced nasal symptoms compared to placebo (P<0.01). Only budesonide reduced allergen-challenge-induced increments of albumin levels in postchallenge nasal lavage fluids (P<0.05, in comparison with placebo). The results suggest that budesonide reduces both seasonal and allergen-challenge-induced nasal symptoms, while levocabastine is effective against allergen-challenge-induced symptoms also during the season. In addition, the topical steroid treatment, but not the antihistamine, inhibits the inflammatory exudation evoked by allergen challenge in patients with active seasonal disease.

The Medical Management of Rhinosinusitis

The management of rhinosinusitis depends on a number of variables related to the duration and severity of symptoms in the individual patient. Furthermore acute rhinosinusitis is managed differently than chronic rhinosinusitis. Because a variety of conservative and pharmacologic interventions are available, the physician can find it difficult to develop a cohesive and logical approach to treatment. An understanding of the pathophysiology, microbiology, and natural history of rhinosinusitis is necessary to formulate the best treatment plan for the individual patient.

An approach to the understanding of the nasal early-phase reaction induced by nasal allergen challenge

Quantitative determinations of the inflammatory mediators in nasal secretions were performed and correlated with the objective nasal symptoms within 1 h after nasal allergen challenge (NAC). Twenty-six patients with seasonal allergic rhinitis were enrolled outside the pollen season. All measurements were performed before (as a baseline control) and at 1, 5, 10, 30, and 60 min after NAC. This study aimed to clarify the pathogenic mechanism of the early-phase reaction (EPR) by monitoring the evolution of early-phase mediators in nasal secretions and the presence of nasal symptoms during this period. The results showed that, after NAC, the maximal mediator concentration was already reached after 1 min for histamine (124 ng/g), 5 min for tryptase (56 microU/g), and 5-10 min for leukotriene C4 (40 ng/g). Itching and sneezing started as early as 20-30 s, and they were predominant symptoms within 5 min. Rhinorrhea and nasal obstruction started a few minutes after NAC and lasted until more than 1 h after NAC. There was no significant correlation between any single mediator and nasal symptoms during the sampling period. In conclusion, this study demonstrated that during the EPR the presence of nasal symptoms involves a complex mechanism, reflecting the interaction between the mediators released by inflammatory cells, and the receptors on different target organs. When evaluating symptoms during the EPR, one must consider not only the severity of these symptoms but also the time period within which these symptoms occur. For the symptoms of nasal obstruction and rhinorrhea, the early-phase reaction often lasted more than 1 h.

Clinical comparison of histamine H1-receptor antagonist drugs

Nearly 40 million Americans have symptoms of upper respiratory allergies, making antihistamines among the most frequently used pharmacologic agents. Although there are mediators of allergic symptoms in addition to histamine, therapy for allergic rhinitis and urticaria has focused upon the use of antihistamines. The classic histamine H1-receptor antagonists, however, are not selective for the H1 site and produce a variety of dopaminergic, serotonergic, and cholinergic responses leading to considerable adverse effects in the central nervous system consequent to both their pharmacologic nonselectivity and their ability to penetrate the blood-brain barrier readily. The second-generation antihistamines were a major advance in the therapy of allergic rhinitis, because they do not penetrate the blood-brain barrier as rapidly and are also designed for greater specificity at H1-receptor. Given their greater selectivity for the H1-receptor, they cause fewer undesirable central nervous system actions, whereas their efficacy is similar to that of the classic antihistamines used in the treatment of allergic rhinitis. Selecting among these antihistamines for the treatment of allergic rhinitis has focused on their pharmacokinetics and adverse effect profiles. The potential cardiotoxic effects of some antihistamines when their metabolism is inhibited requires caution in prescribing these agents. The antiallergic and antiasthmatic effects of several newer antihistamines are being explored. For the clinician, making the therapeutic decision among H1-receptor antagonists requires a comprehensive knowledge of their diverse effects.

Effect of cetirizine on antigen-induced tracheal contraction of passively sensitized guinea pigs

BACKGROUND

Cetirizine dihydrochloride (cetirizine), a potent histamine H1-receptor antagonist, has been developed as an anti-allergy drug.

OBJECT

The anti-allergic effects and mechanism of cetirizine were studied using in vitro assay systems.

METHODS

We investigated the effect of cetirizine on antigen-induced contractions of isolated tracheal strips and on chemical mediator release from antigen-stimulated lung chips taken from passively sensitized guinea pigs. We examined the antigen-induced mobilization of Ca2+ in MC/9 mast cells sensitized with IgE.

RESULTS

Cetirizine inhibited the antigen-induced contraction of isolated guinea-pig trachea concentration dependently. Pyrilamine, another histamine H1-receptor antagonist, delayed the response but did not change the maximum amplitude. Cetirizine at the concentration of 3 microM also inhibited the antigen-induced release of histamine, leukotriene D4, and leukotriene E4 from guinea pig lung chips. Furthermore, it inhibited the antigen-induced Ca2+ increase in MC/9 mast cells, whereas pyrilamine did not.

CONCLUSION

These findings suggest that one anti-allergic mechanism of cetirizine may inhibit mediator release which is, at least partially, mediated by a decrease in the transient Ca2+ influx in mast cells.

The effect of cetirizine and loratadine on codeine-induced histamine release in human skin in vivo assessed by cutaneous microdialysis

OBJECTIVE AND DESIGN

To determine whether or not cetirizine and loratadine inhibit codeine- induced histamine release in human skin in vivo, we conducted a placebo-controlled double-blind trial in which histamine release was assessed by dermal microdialysis.

SUBJECTS

A group of ten normal volunteers were studied, each subject visiting the laboratory on three occasions with intervals of at least 2 weeks between visits.

TREATMENT

Cetirizine, loratadine (both 10 mg) or placebo was given orally 4 h before provocation of weal and flare responses in the skin by intradermal injection of 25 microliters of 3 or 10 mg/ml codeine 1 mm from the centre of individual 216 microns diameter microdialysis fibres inserted in the dermis.

METHODS

Dialysate was collected at 2 min intervals for 4 min before and 20 min after codeine injection and histamine assayed spectrofluorometrically. Weal and flare responses to codeine were assessed in the opposite arm.

RESULTS

Histamine concentrations in the microdialysis fibre outflow with 3 and 10 mg/ml codeine were maximal at 2-4 min when 910 +/- 156 and 1194 +/- 304 nM respectively were found in the placebo group. Cetirizine and loratadine did not modify either the kinetics or total histamine release while significantly (p < 0.01) inhibiting weal and flare responses.

CONCLUSIONS

Neither cetirizine nor loratadine inhibited codeine-induced histamine release or modified the time course of its release in human skin in vivo when given in clinically used doses which are sufficient to significantly reduce weal and flare responses.

The effect of cetirizine on sulfidoleukotriene production by blood leukocytes in children with allergic rhinitis

Twelve children with allergic rhinitis due to monosensitivity to Dermatophagoides pteronyssinus (Dp) took part in a placebo-controlled, double-blind, crossover study to evaluate the effect of cetirizine, a second-generation, nonsedating H1-blocker-type antihistamine, on sulfidoleukotriene releasability by blood leukocytes and to determine its correlation with clinical findings and nasal challenge scores. Sulfidoleukotriene release by blood leukocytes was determined by the cellular allergen stimulation test (CAST), which measures leukotriene (LT)C4, LTD4, and LTE4, all in one assay. Compared to placebo, cetirizine significantly (P < 0.05) decreased daily symptom scores of nasal discharge, nasal itching, and sneezing, as well as the number of sneezings after nasal challenge with the antigen, without alleviating nasal obstruction (P > 0.05). It also suppressed both early (P < 0.05) and late skin reactions to intradermal tests. Although cetirizine did not influence in vitro sulfidoleukotriene production by blood leukocytes with buffer or anti-IgE (P > 0.05), it substantially reduced the release of these mediators upon challenge with Dp antigen. Furthermore, there was a high correlation between the number of sneezes after challenge and the amount of sulfidoleukotriene released in nine patients (r = 0.78; P < 0.01). It is concluded that the amount of sulfidoleukotrienes produced by blood leukocytes in vitro may reflect the nasal hyperreactivity of the patient, and that cetirizine, which is highly effective in the treatment of allergic rhinitis, owes part of its effect to inhibition of sulfidoleukotriene releasability by blood leukocytes in children.

Effects of loratadine on anti-IgE-induced inflammation, histamine release, and leukocyte recruitment in skin of atopics

The aim of this study was to assess the ability of the H1-receptor antagonist loratadine to modify anti-IgE-induced cutaneous wheal-and-flare and late-phase reactions (WFR and LPR), as well as histamine release and leukocyte accumulation in skin chambers. For this purpose, 10 atopics with allergic rhinitis were entered into a double-blind crossover study in which they received either placebo or loratadine (20 mg/day orally) for 8 days separated by a 7-day washout period. Blisters were induced on both forearms on day 7 of each treatment period, and were unroofed on day 8 and covered with plastic skin chambers. Chamber fluids were collected during 7 h after 1-h incubation with anti-IgE or control IgG. Intradermal challenge with histamine and anti-IgE was performed at the same occasion. As compared to placebo treatment, loratadine inhibited the immediate WFRs to anti-IgE by 35% (wheal) and 65% (flare), respectively (P < 0.01), and corresponding reactions to histamine challenge by 50% and 70% (P < 0.001), respectively. Moreover, the initial phase (0-2 h) of the LPR induced by anti-IgE was attenuated by up to approximately 60% (P < 0.001) during loratadine treatment. Thereafter, no inhibition of the LPR was observed. The magnitude and time course of histamine release into skin chambers was virtually the same after loratadine and placebo treatment, with a peak during 0-1 h and a progressive decline during the following 2 h. Accumulation of alpha 2-macroglobulin, reflecting extravasation of large plasma proteins, also peaked during the first hour and was unaffected by loratadine during the 8-h observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacologic heterogeneity of human lung and colon cells: effect of terfenadine and cetirizine

H1-blockers may have antiallergic properties which cause the blocking of eicosanoid release, and the effect of these drugs may differ according to the phenotype of mast cells. This study examined the ability of terfenadine and cetirizine to inhibit the release of arachidonic acid-derived mediators from human lung and colon cells. Dispersed cells were challenged with anti-IgE in the presence or absence of 10 microM of terfenadine or cetirizine, and the release of prostaglandin (PG)D2 and leukotriene (LT)C4/D4 was assessed by enzyme immunoassay (EIA). Terfenadine caused significant inhibition of both PGD2 and LTC4/D4 (49 +/- 9 and 29 +/- 19%, respectively) from human lung cells but had a less marked effect on PGD2 release from human colon cells (21 +/- 9% for PGD2 and 18 +/- 9% for LTC4/D4). In contrast, although cetirizine caused significant inhibition of both mediators measured in lung cells (38 +/- 16% for PGD2 and 34 +/- 19% for LTC4), it did not cause any significant inhibition of either mediator from human colon cells. These findings suggest that H1-antagonists may have additional properties, and the differential effects of cetirizine on lung and colon tissue may indicate differences in mast cell phenotype.

Cetirizine reduces inflammatory cell recruitment and ICAM-1 (or CD54) expression on conjunctival epithelium in both early- and late-phase reactions after allergen-specific challenge

BACKGROUND

Allergen-specific conjunctival challenge (ASCC) is a safe and reproducible experimental model of allergic conjunctivitis and a useful tool in the evaluation of effectiveness and possible mechanisms of action of drugs commonly used in the treatment of allergic diseases.

OBJECTIVE

The protective effect of cetirizine on inflammatory changes after ASCC was assessed in 12 patients with rhinoconjunctivitis caused by Parietaria judaica in a double-blind study.

METHODS

After a screening ASCC was performed, patients were randomized into two treatment groups; each patient was given cetirizine (oral tablets) 10 mg twice daily, or matching placebo for 3 1/2 days in off-pollen season. Clinical evaluation (itching, hyperemia, lacrimation, and swelling of eyelids) and cytologic assessment (number of inflammatory cells in conjunctival scraping and evaluation of intercellular adhesion molecule-1 (ICAM-1)/CD54 expression on epithelial cells) were performed at baseline, 30 minutes (i.e., early-phase reaction [EPR]), 6 hours, and 24 hours (i.e., late-phase reaction [LPR]) after ASCC, before and after treatment.

RESULTS

The EPR clinical events and the EPR total number of inflammatory cells were significantly reduced by cetirizine compared with placebo. The LPR clinical events and inflammatory cell recruitment were reduced by cetirizine in a similar manner. Both eosinophil and neutrophil numbers were decreased by active drug in EPR and LPR. Furthermore, ICAM-1/CD54 expression was significantly reduced by cetirizine in both the EPR and LPR compared with placebo.

CONCLUSIONS

This study shows that cetirizine has a protective effect on clinical and cellular EPR and LPR events (including ICAM-1/CD54 expression on epithelium) induced by ASCC.

Nasal histamine challenge in nonallergic and allergic subjects evaluated by acoustic rhinometry

Nasal patency shows spontaneous variations but is influenced by a number of factors like exercise and allergic conditions. Nasal histamine challenge has been used to define nasal hypersensitivity. We have applied acoustic rhinometry as a new objective method to study the spontaneous variations of the nasal mucosa and its response to histamine challenge in 12 nonallergic subjects and 12 subjects with nasal allergy to pollen, but out of the pollen season. Measurements of the minimum cross-sectional area and the volume of the nasal cavities were done every 15 min for 6 h. More pronounced spontaneous variations, defined by the coefficient of variation of the measurements, were encountered in the allergic than in the nonallergic subjects, especially with regard to the minimum cross-sectional areas in the nasal cavities (P < 0.02). Allergic subjects showed increased sensitivity to histamine, as compared with nonallergic subjects, during low-concentration (0.1%) challenge (P < 0.05) and a prolonged effect of histamine challenge (P = 0.01). Antihistamine (cetirizine) had a significant effect on the histamine-induced symptoms and decrease of nasal dimensions during histamine challenge, but no significant effect on pollen-induced changes. In the allergic group, the decrease in minimum area during allergen provocation correlated with the level of specific IgE (r = 0.81; P = 0.0015).

The pharmacology and use of H1-receptor-antagonist drugs

The second-generation H1-antagonist drugs are supplanting their predecessors in the treatment of allergic rhinoconjunctivitis and chronic urticaria. Their use can be justified mainly on the basis of a more favorable risk-benefit ratio, because they are less toxic to the central nervous system. Future research into H1 antagonists should include additional dose-response studies in patients with allergic disorders, especially children and the elderly; objective studies of adverse effects; studies of topical mucosal application of H1 antagonists; and studies of H1-antagonist enantiomers and active metabolites. With the cloning of the gene encoding the H1 receptor and increased understanding of the precise structural requirements for H1-receptor activity, H1 antagonists with an even more favorable therapeutic index may be developed.

The effect of terfenadine on unilateral nasal challenge with allergen

To investigate the role of H1 receptor-mediated effects in allergic rhinitis, we challenged 12 allergic volunteers with allergen 2 hours after administration of either placebo or 60 mg of terfenadine. Filter paper discs were used for the unilateral administration of allergen and the collection of nasal secretions. Secretion weights, levels of histamine in recovered nasal secretions, and nasal airway resistance (NAR) were measured for each nostril separately, and the number of sneezes was counted. After placebo treatment, allergen challenge led to significant increases in ipsilateral and contralateral secretion weights, ipsilateral histamine levels, ipsilateral NAR, and sneezing. Contralateral histamine levels were not elevated. H1 antagonism with terfenadine markedly reduced the number of sneezes and partially decreased ipsilateral and contralateral secretion weights, without affecting the increase in NAR. Terfenadine premedication also lowered the amount of histamine in ipsilateral secretions after allergen challenge. Performing identical nasal challenges with a 10-fold lower dose of antigen produced similar results. Previous studies showed that terfenadine had no effect on methacholine provocation and completely abolished ipsilateral and contralateral secretion weights after histamine challenge. We conclude that sneezing after allergen challenge is caused almost exclusively by a reflex initiated through H1 receptors and that H1 antagonism has no influence on allergen-induced increases in NAR. Unilateral allergen challenge leads to bilateral increases in secretion weights, which are only partially inhibited by terfenadine, suggesting the involvement of mediators other than histamine in the nasonasal reflex. As reported earlier, terfenadine also decreases allergen-induced histamine release after challenge with the highest dose of antigen.

The effect of antihistamines on the immediate allergic response: a comparative review

Antihistamines are believed to reduce the sneezing and rhinorrhea associated with allergic rhinitis, primarily by competitive antagonism of histamine for H1 cellular receptors, but additional mechanisms of action may contribute to their clinical efficacy. To improve our understanding of H1 antihistamine action, we studied the effects of pretreatment with terfenadine, cetirizine, ketotifen, azatadine, diphenhydramine, and azelastine on increases in vascular permeability, mast cell activation, and sneezing induced by nasal challenge with antigen. All studied antihistamines reduced sneezing, indicating that they all effectively antagonize histamine after its release. In addition, terfenadine and topically administered azatadine blocked the release of histamine. Studies with cetirizine and azelastine revealed that these antihistamines significantly reduced sulfidopeptide leukotriene levels. Terfenadine and azelastine also reduced kinin production. These results confirm that antihistamines are effective in reducing sneezing and, in some cases, vascular permeability. The findings of these studies also illustrate that the various antihistamines have multiple and different mechanisms of action that may have implications for their clinical uses.

Suppression by cetirizine of pleurisy triggered by antigen in actively sensitized rats

The efficacy of cetirizine in comparison with meclizine, another piperazine H1 receptor antagonist, in rat pleurisy caused by allergen or autacoid was investigated. Sensitization was achieved by subcutaneous injection of a mixture of ovalbumin and aluminium hydroxide. Fourteen days later, the animals were challenged with an intrathoracic injection of ovalbumin (12 micrograms/cavity), which caused drastic mast cell degranulation, followed by pleural oedema and leucocyte influx. Cetirizine and meclizine (2.5-30 mg/kg i.p.), 1 h before challenge, inhibited the exudatory response evoked by antigen, under conditions where neutrophil and eosinophil accumulation was affected only by the former. When administered intrathoracically 22 h after allergen, i.e. using a curative approach, cetirizine (15 micrograms/cavity) drastically reduced the pleural eosinophilia noted 24 h post-challenge, indicating that this drug can reverse an already established eosinophilia. Cetirizine (15 mg/kg i.p.) also restored, to about 39% (P < 0.001), the number of uninjured mast cells recovered from the pleural cavity following allergen stimulation. In normal rats, cetirizine (5-15 micrograms/cavity) completely inhibited the pleural exudation elicited by histamine and only partially the exudation caused by 5-hydroxytryptamine or bradykinin, but was quite inactive against platelet-activating factor. We conclude that the pleural exudation triggered by allergen, vasoactive amines or bradykinin is clearly sensitive to cetirizine. In addition, the ability of the drug to interfere with pleural neutrophil or eosinophil mobilization and mast cell degranulation seems not to be associated with its ability to block the histamine H1 receptor.

Modulation of eicosanoid and histamine release from human dispersed lung cells by terfenadine

Terfenadine is an H1-blocker that may have antiallergic properties. A study was carried out to examine the ability of terfenadine to inhibit the release of histamine and arachidonic-acid-derived mediators from human lung cells. Cells were dispersed from fresh human lung tissue obtained from four accident victims whose hearts were donated for transplantation and four lung cancer resections. Cells were dispersed by enzymatic digestion with type XIV protease and chymopapain, and this resulted in a cell population containing approximately 5% mast cells. The remaining cells were mainly macrophages. The cells were challenged with anti-IgE at a 1/1000 dilution. Cells were challenged without terfenadine and after a preincubation of 0.1, 1, and 10 mumol terfenadine. The release of PGD2 and LTC4/D4 was assessed with an EIA. Histamine was assayed by RIA with a monoclonal antibody against acylated histamine. A release of both eicosanoids and histamine was observed in all experiments. An inhibition of eicosanoids was observed at both 1 and 10 mumol terfenadine (median percentage of inhibition of PGD2: 38.00 +/- 15.65 and 56.00 +/- 13.12; median percentage of inhibition of LTC4/D4: 37.5 +/- 19.80 and 52.5 +/- 26.8). On the other hand, histamine release was not blocked by terfenadine. Terfenadine inhibits, in a dose-dependent manner, the release of eicosanoids after challenge of dispersed lung cells by anti-IgE, and this effect may have some clinical relevance.

Inhibition of mediator release during the early reaction to antigen

A nasal lavage model and a new filter paper disk model have been used to measure biologic and physiologic responses to antigen challenge in patients with allergic rhinitis. Pretreatment of subjects with cetirizine reduced the number of sneezes induced by antigen challenge but did not significantly reduce levels of histamine or prostaglandin D2 in a double-blind, placebo-controlled trial with the lavage model. Pretreatment with 60 or 300 mg of terfenadine did significantly reduce levels of histamine, kinin, albumin, and TAME-esterase activity in a double-blind, placebo-controlled study with this model. Again with the nasal lavage model, a double-blind, placebo-controlled comparison of pretreatment with 60 mg of terfenadine or 10 mg of loratadine showed that both agents significantly reduced sneezing. Both drugs also lowered levels of antigen-induced histamine and TAME-esterase, but only terfenadine did so significantly. In a double-blind, placebo-controlled study, the new disk method showed that terfenadine reduced sneezing but not nasal congestion in eight patients with allergic rhinitis. Terfenadine significantly reduced the weight of nasal secretions on both sides of the nose and significantly reduced histamine on the ipsilateral side.

The effect of azelastine on the early allergic response

To study the effect of azelastine on the immediate reaction to nasal allergen challenge, we performed a double blind, placebo-controlled cross-over clinical trial. Thirteen subjects with seasonal allergic rhinitis underwent nasal challenge with antigen 4 hr after a single oral 2 mg dose of azelastine. The response was monitored by counting the number of sneezes and by measuring the levels of histamine, prostaglandin D2, immunoreactive sulphidopeptide leukotrienes, kinis and TAME-esterase activity in recovered nasal lavages. After a single dose of azelastine, there was a significant reduction in sneezing (10 vs 2, P = 0.01) and in the median levels of recovered TAME-esterase activity (63.1 vs 17.5 c.p.m. x 10(-3), P = 0.01), immunoreactive sulphidopeptide leukotrienes (7.5 vs 2.1 ng/ml, P = 0.03) and kinins (1370 vs 251 pg/ml, P = 0.03), with no significant reduction in the median levels of histamine (3.7 vs 1.2 ng/ml, P = 0.2) and prostaglandin D2 (70 vs 70 pg/ml, P = 0.2) compared to placebo (numbers represent total increase over diluent challenge). These results suggest that azelastine does not inhibit mast cell activation but affects the consequences of released histamine, namely sneezing, increased vascular permeability and the generation of kinins. The results further suggest that other cells, in addition to mast cells, might be responsible for the generation of leukotrienes during the early allergic response, and that azelastine reduces their ability to generate this mediator or that inhibition of leukotriene release from mast cells occurs at lower drug concentrations.

Suppressive effect of loratadine on allergen-induced histamine release in the nose

It has been speculated whether the recently developed non-sedating antihistamines may possess other properties than merely being antagonists at the H1-receptors. To investigate this suggestion 12 patients with strictly seasonal allergic rhinitis participated in a double-blind placebo controlled randomized cross-over study outside the pollen season. At steady state levels of 10 mg loratadine, a new non-sedating antihistamine, the patients were challenged with methacholine. This was followed by a nasal challenge with increasing doses of allergen. 24 h later the patients were rechallenged nasally with the same methacholine dose as the day before. The volume of the methacholine-induced nasal secretion was measured and the response to allergen was determined by scoring technique. In returned nasal lavage fluid the levels of histamine and TAME-esterase activity were measured. It was found that loratadine significantly reduced the immediate allergic nasal symptoms compared with placebo (P less than 0.01). Loratadine also reduced the allergen-induced release of histamine into the nasal cavity after the strongest allergen dose, from 9.6 +/- 1.5 (mean +/- SEM) to 6.4 +/- 1.4 ng/ml (P less than 0.05). A similar decrease in the TAME-esterase activity after treatment with loratadine was observed. The TAME-esterase activity decreased from 11.6 *10(3) +/- 2.47 *10(3) to 5.60 *10(3) +/- 1.45 *10(3) CMP (P less than 0.05). There were no significant changes between the active and placebo treatments regarding the methacholine-induced secretory response. This was true for the initial methacholine challenge as well as the secretory response 24 h later.(ABSTRACT TRUNCATED AT 250 WORDS)

A gap in surface therapy: topical antihistamines

Allergic and non-allergic rhinitis have been treated by many drugs with different modes of action such as topical disodium cromoglycate and ipratropium bromide, systemic antihistamines and corticosteroid drugs and topical corticosteroids. Yet, these therapies are not entirely satisfactory for all symptoms. The rationale for the topical, intranasal use of antihistamines in patients is discussed. Topical antihistamine agents are administered in order to avoid the side effects of systematically applied medications, and to reach higher local drug concentrations. H1 receptors of the nasal mucosa play an important role in the physiopathology of allergic and non-allergic rhinitis and even of infectious rhinitis. Most studies using topical antihistamines in rhinitis, had an experimental physiopathological aim and did not explore clinical efficacy. Recently, topical application of levocabastine--a potent H1 antagonist--yielded good clinical results in allergic conjunctivitis, seasonal allergic rhinoconjunctivitis, and non allergic perennial rhinitis.

The effects of antihistamines beyond H1 antagonism in allergic inflammation

Antigen and cold dry air were used to challenge the upper and lower airways, skin, and conjunctiva. In each of these four systems an immediate and late-phase reaction to antigen is well characterized. Although the pattern of mediator release is different in these four areas, the degree of infiltration of basophils and eosinophils in the late-phase reaction appears to be constant. Of a number of drugs that can influence these mediators and cell responses, the steroids represent a typical mode of action. Steroids block the late-phase response and ablate the eosinophil and basophil infiltration. Although the effects of antihistamines appear to be similar, they do not appear to be caused by H1 antagonism; the mechanism of their action is unknown. This discussion will focus on these non-H1 antagonist effects of antihistamines in four challenge models, particularly the upper airways and skin.

Cetirizine. A review of its pharmacological properties and clinical potential in allergic rhinitis, pollen-induced asthma, and chronic urticaria

Cetirizine, a piperazine derivative and carboxylated metabolite of hydroxyzine, is a potent histamine H1-receptor antagonist with antiallergic properties. It has marked affinity for peripheral histamine H1-receptors and, at the standard dose of 10mg daily, lacks the CNS depressant effects of standard antihistamines. In addition, it inhibits histamine release and eosinophil chemotaxis during the secondary phase of the allergic response. Results from controlled clinical trials indicate that cetirizine is an effective and well tolerated treatment of seasonal and perennial allergic rhinitis and chronic idiopathic urticaria. Cetirizine appears to be as effective as conventional dosages of terfenadine, chlorpheniramine and hydroxyzine in relieving symptoms associated with these disorders and produces a markedly lower incidence of sedation than chlorpheniramine, hydroxyzine and several other standard antihistamines. Thus, cetirizine appears to provide a useful alternative to other 'nonsedating' antihistamines; cetirizine may also have a future role in the treatment of allergic asthma and certain forms of physical urticaria.

Ketotifen reduces sneezing but not histamine release following nasal challenge with antigen

We evaluated the effect of pre-treatment with 1 and 2 mg b.i.d. of ketotifen on the early response to nasal challenge in a double-blind cross-over trial. Weekly nasal challenges were performed in 10 allergic subjects after 1 hr and 1, 2, 3 and 4 weeks of ketotifen administration. The response to nasal challenge was monitored by counting the number of sneezes, the assessment of subjective symptoms, and by measuring the levels of histamine and TAME-esterase activity in recovered nasal lavages. The number of sneezes diminished significantly after a single dose of drug with both the 1 and 2 mg doses. Prolonged pre-treatment did not improve the results. The levels of histamine and TAME-esterase activity in recovered nasal lavages were not changed significantly by either pre-treatment at either dose. Although the number of subjects was small, our data suggest that ketotifen diminishes allergic symptomatology by its antihistaminic properties rather than by inhibiting histamine release from mast cells. As we did not look into the effects of ketotifen on other products generated by mast cells (prostanoids, leukotrienes and tryptase), we cannot fully rule out an effect on mast cells.