New insights into the second generation antihistamines

The histamine receptor H1 acts as an alternative receptor for SARS-CoV-2

Numerous host factors, in addition to human angiotensin-converting enzyme 2 (hACE2), have been identified as coreceptors of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), demonstrating broad viral tropism and diversified druggable potential. We and others have found that antihistamine drugs, particularly histamine receptor H1 (HRH1) antagonists, potently inhibit SARS-CoV-2 infection. In this study, we provided compelling evidence that HRH1 acts as an alternative receptor for SARS-CoV-2 by directly binding to the viral spike protein. HRH1 also synergistically enhanced hACE2-dependent viral entry by interacting with hACE2. Antihistamine drugs effectively prevent viral infection by competitively binding to HRH1, thereby disrupting the interaction between the spike protein and its receptor. Multiple inhibition assays revealed that antihistamine drugs broadly inhibited the infection of various SARS-CoV-2 mutants with an average IC50 of 2.4 µM. The prophylactic function of these drugs was further confirmed by authentic SARS-CoV-2 infection assays and humanized mouse challenge experiments, demonstrating the therapeutic potential of antihistamine drugs for combating coronavirus disease 19.IMPORTANCEIn addition to human angiotensin-converting enzyme 2, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can utilize alternative cofactors to facilitate viral entry. In this study, we discovered that histamine receptor H1 (HRH1) not only functions as an independent receptor for SARS-CoV-2 but also synergistically enhances ACE2-dependent viral entry by directly interacting with ACE2. Further studies have demonstrated that HRH1 facilitates the entry of SARS-CoV-2 by directly binding to the N-terminal domain of the spike protein. Conversely, antihistamine drugs, primarily HRH1 antagonists, can competitively bind to HRH1 and thereby prevent viral entry. These findings revealed that the administration of repurposable antihistamine drugs could be a therapeutic intervention to combat coronavirus disease 19.

Mast cell-mediated immune regulation in health and disease

Mast cells are important components of the immune system, and they perform pro-inflammatory as well as anti-inflammatory roles in the complex process of immune regulation in health and disease. Because of their strategic perivascular localization, sensitivity and adaptability to the microenvironment, and ability to release a variety of preformed and newly synthesized effector molecules, mast cells perform unique functions in almost all organs. Additionally, Mast cells express a wide range of surface and cytoplasmic receptors which enable them to respond to a variety of cytokines, chemicals, and pathogens. The mast cell's role as a cellular interface between external and internal environments as well as between vasculature and tissues is critical for protection and repair. Mast cell interactions with different immune and nonimmune cells through secreted inflammatory mediators may also turn in favor of disease promoting agents. First and forefront, mast cells are well recognized for their multifaceted functions in allergic diseases. Reciprocal communication between mast cells and endothelial cells in the presence of bacterial toxins in chronic/sub-clinical infections induce persistent vascular inflammation. We have shown that mast cell proteases and histamine induce endothelial inflammatory responses that are synergistically amplified by bacterial toxins. Mast cells have been shown to exacerbate vascular changes in normal states as well as in chronic or subclinical infections, particularly among cigarette smokers. Furthermore, a potential role of mast cells in SARS-CoV-2-induced dysfunction of the capillary-alveolar interface adds to the growing understanding of mast cells in viral infections. The interaction between mast cells and microglial cells in the brain further highlights their significance in neuroinflammation. This review highlights the significant role of mast cells as the interface that acts as sensor and early responder through interactions with cells in systemic organs and the nervous system.

The role of SeDeM for characterizing the active substance and polyvinyilpyrrolidone eliminating metastable forms in an oral lyophilizate-A preformulation study

A preformulation study of an oral lyophilisate with cetirizine dihydrochloride (CTZ) as active ingredient, mannitol and PVP K30 as bulking agents is presented. CTZ shown a humidity content of 0.150% and a spontaneous hygroscopicity of 0.200% (both determined by SeDeM diagram), demonstrating an adequate stability behavior in solid form. A design of experiments (DoE) performed with both mannitol and PVP K30, followed by a simple factorial design (3²) has determined the optimum combination of excipients and CTZ, and showed that a higher proportion of PVP K30 was able to prevent metastable forms generated by mannitol.

Consensus Statement for the Diagnosis and Treatment of Urticaria: A 2017 Update

This article is developed by the Skin Allergy Research Society of India for an updated evidence-based consensus statement for the management of urticaria, with a special reference to the Indian context. This guideline includes updated definition, causes, classification, and management of urticaria. Urticaria has a profound impact on the quality of life and causes immense distress to patients, necessitating effective treatment. One approach to manage urticaria is by identification and elimination of the underlying cause(s) and/or eliciting trigger(s) while the second one is by treatment for providing symptomatic relief. This guideline recommends the use of second-generation nonsedating H1-antihistamines as the first-line treatment. The dose can be increased up to four times to meet the expected results. In case patients still do not respond, appropriate treatment options can be selected depending on the associated medical condition, severity of the symptoms, affordability of the drugs, and accessibility of modern biologics such as omalizumab.

The role of antihistamines in asthma management

Histamine is an important mediator in airway inflammation. It is elevated in the airways of asthmatic patients and is responsible for many of the pathophysiological features in asthma. Antihistamines block the actions of histamine and also have effects on inflammation which is independent of histamine-H(1)-receptor antagonism. Antihistamines have been shown to have bronchodilatory effects, effects on allergen-, exercise-, and adenosine-monophosphate-challenge testing, and also to prevent allergen-induced nonspecific airways hyperresponsiveness. Clinical studies have shown mixed results, and some studies have reported beneficial effects of azelastine, cetirizine, desloratadine, and fexofenadine on asthma symptoms or physiological measures in patients with asthma. The combination of an antihistamine and a leukotriene receptor antagonist has been shown to have additive effects in certain studies. Antihistamines have also been shown to delay or prevent the development of asthma in a subgroup of atopic children. These data suggest that antihistamines may have beneficial effects in the management of asthma.

Mast Cell: A Multi-Functional Master Cell

Mast cells are immune cells of the myeloid lineage and are present in connective tissues throughout the body. The activation and degranulation of mast cells significantly modulates many aspects of physiological and pathological conditions in various settings. With respect to normal physiological functions, mast cells are known to regulate vasodilation, vascular homeostasis, innate and adaptive immune responses, angiogenesis, and venom detoxification. On the other hand, mast cells have also been implicated in the pathophysiology of many diseases, including allergy, asthma, anaphylaxis, gastrointestinal disorders, many types of malignancies, and cardiovascular diseases. This review summarizes the current understanding of the role of mast cells in many pathophysiological conditions.

Determination of stress-induced degradation products of cetirizine dihydrochloride by a stability-indicating RP-HPLC method

BACKGROUND

A new, simple and accurate stability-indicating reverse phase high performance liquid chromatography method was developed and validated during the early stage of drug development of an oral lyophilizate dosage form of cetirizine dihydrochloride.

METHODS

For RP-HPLC analysis it was used an Eclipse XDB C8 column 150 mm × 4.6 mm, 5 μm (Agilent columns, Barcelona, Spain) as the stationary phase with a mobile phase consisted of a mixture of 0.2 M K2HPO4 pH 7.00 and acetonitrile (65:35, v/v) at a flow rate of 1 mL min (-1). Detection was performed at 230 nm using diode array detector. The method was validated in accordance with ICH guidelines with respect to linearity, accuracy, precision, specificity, limit of detection and quantification.

RESULTS

The method results in excellent separation between the drug substance and its stress-induced degradation products. The peak purity factor is >950 for the drug substance after all types of stress, which confirms the complete separation of the drug substance peak from its stress induced degradation products. Regression analysis showed r(2) > 0.999 for cetirizine dihydrochloride in the concentration range of 650 μg mL (-1) to 350 μg mL(-1) for drug substance assay and a r(2) > 0.999 in the concentration range of 0.25 μg mL(-1) to 5 μg mL(-1) for degradation products. The method presents a limit of detection of 0.056 μg mL (-1) and a limit of quantification of 0.25 μg mL(-1). The obtained results for precision and accuracy for drug substance and degradation products are within the specifications established for the validation of the method.

CONCLUSIONS

The proposed stability-indicating method developed in the early phase of drug development proved to be a simple, sensitive, accurate, precise, reproducible and therefore useful for the following stages of the cetirizine dihydrochloride oral lyophilizate dosage form development.

Bilastine: a new nonsedating oral H1 antihistamine for treatment of allergic rhinoconjunctivitis and urticaria

Bilastine is a new, well-tolerated, nonsedating H1 receptor antihistamine. In the fasting state bilastine is quickly absorbed, but the absorption is slowed when it is taken with food or fruit juice. Therefore, it is recommended that bilastine is taken at least one hour before and no sooner than two hours after a meal. Clinical studies sponsored by the manufacturer have shown that bilastine 20 mg once daily is as efficacious as other nonsedating antihistamines in allergic rhinoconjunctivitis and chronic urticaria in individuals from 12 and 18 years of age, respectively. Bilastine is efficacious in all nasal symptoms including obstruction and in eye symptoms. The observations indicate that non-sedating antihistamines, as opposed to what has been thought previously, may be helpful in patients with allergic rhinitis in whom nasal obstruction is a major concern. Current international guidelines need to be revised in the light of the recent evidence. Research into aspects of pharmacokinetics and efficacy and adverse effect profiles of bilastine in children under 12 years of age is needed as are dose-response assessments and studies planned rigorously with the aim of assessing quality of life effects.

The impact of P-glycoprotein mediated efflux on absorption of 11 sedating and less-sedating antihistamines using Caco-2 monolayers

Caco-2 cells were used to compare P-gp mediated efflux and passive permeability using bidirectional transport of 11 antihistamines. An efflux ratio >2 indicated active efflux, with PSC833 and GF120918 used as functional P-gp inhibitors. Antihistamines were measured directly by HPLC or LC/MS. Fexofenadine had an efflux ratio of 37, yet had negligible passive permeability, even in the presence of a pH gradient (0.1 × 10(-6) cm/sec). Its precursor, terfenadine, had an efflux ratio of 2.5, while cetirizine, desloratadine and hydroxyzine were 4, 7 and 14, respectively. After incubation with P-gp inhibitors, these ratios dropped significantly. Loratadine, by contrast, had equivalent transport in both directions and passive permeability was high (24 × 10(-6) cm/sec). Dimenhydrinate was the only other sedating antihistamine to exhibit efflux, with a ratio of 10. Gradient conditions of pH (6/7.4) increased efflux of terfenadine and desloratadine to over 31 and 38 fold respectively, yet this increased efflux was not associated with P-gp. Altering functional P-gp in the gut is likely to influence absorption of some sedating antihistamines such as dimenhydrinate and hydroxyzine and most less-sedating antihistamines except loratadine. In addition, desloratadine exhibits pH dependent efflux which could further induce variable absorption of this antihistamine.

The anti-inflammatory effects of levocetirizine--are they clinically relevant or just an interesting additional effect?

Levocetirizine, the R-enantiomer of cetirizine dihydrochloride has pharmacodynamically and pharmacokinetically favourable characteristics, including rapid onset of action, high bioavailability, high affinity for and occupancy of the H1-receptor, limited distribution, minimal hepatic metabolism together with minimal untoward effects. Several well conducted randomised clinical trials have demonstrated the effectiveness of levocetirizine for the treatment of allergic rhinitis and chronic idiopathic urticaria in adults and children. In addition to the treatment for the immediate short-term manifestations of allergic disease, there appears to be a growing trend for the use of levocetirizine as long-term therapy. In addition to its being a potent antihistamine, levocetirizine has several documented anti-inflammatory effects that are observed at clinically relevant concentrations that may enhance its therapeutic benefit. This review will consider the potential or otherwise of the reported anti-inflammatory effects of levocetirizine to enhance its effectiveness in the treatment of allergic disease.

Levocetirizine in the treatment of allergic diseases

BACKGROUND

Levocetirizine, the R-enantiomer of cetirizine dihydrochloride, is a new molecule with a potent and selective antihistamine activity.

OBJECTIVE

To investigate the evidence that levocetirizine is an effective therapy for allergic disease.

METHODS

Evaluation of published articles in English, or having an English abstract.

RESULTS

Clinical trials indicate that levocetirizine is safe and effective for the treatment of allergic rhinitis and chronic idiopathic urticaria. The compound shows a rapid onset of action, high bioavailability and affinity for the H1 receptor. Moreover, this molecule demonstrates many anti-inflammatory effects that enhance the clinical therapeutic benefit not only in short-term but also in long-term treatments, as reported in recent trials utilizing levocetirizine for several months.

CONCLUSION

Levocetirizine confirms its safe effective activity for treatment of allergic disease in both adults and children.

Synthesis, structure-affinity relationships, and modeling of AMDA analogs at 5-HT2A and H1 receptors: structural factors contributing to selectivity

Histamine H(1) and serotonin 5-HT(2A) receptors present in the CNS have been implicated in various neuropsychiatric disorders. 9-Aminomethyl-9,10-dihydroanthracene (AMDA), a conformationally constrained diarylalkyl amine derivative, has affinity for both of these receptors. A structure-affinity relationship (SAFIR) study was carried out studying the effects of N-methylation, varying the linker chain length and constraint of the aromatic rings on the binding affinities of the compounds with the 5-HT(2A) and H(1) receptors. Homology modeling of the 5-HT(2A) and H(1) receptors suggests that AMDA and its analogs, the parent of which is a 5-HT(2A) antagonist, can bind in a fashion analogous to that of classical H(1) antagonists whose ring systems are oriented toward the fifth and sixth transmembrane helices. The modeled orientation of the ligands are consistent with the reported site-directed mutagenesis data for 5-HT(2A) and H(1) receptors and provide a potential explanation for the selectivity of ligands acting at both receptors.

Disposition of loratadine in healthy volunteers

The absorption, metabolism and excretion of carbon-14-labeled loratadine (LOR, SCH 29851, Claritin) administered orally to healthy male volunteers were evaluated. Following a single oral 10-mg dose of [(14)C]LOR ( approximately 102 microCi), concentrations of LOR and desloratadine (DL; a pharmacologically active descarboethoxy metabolite of LOR) were determined in plasma. Metabolites in plasma, urine and feces were characterized using a liquid chromatography-mass spectrometry system (LC-MS) connected in line with a flow scintillation analyzer (FSA). Maximum plasma LOR and DL concentrations were achieved at 1.5 h and 1.6 h, respectively; thus, LOR was rapidly absorbed but also rapidly metabolized as indicated by these similar t(max) values. Metabolite profiles of plasma showed that LOR was extensively metabolized via descarboethoxylation, oxidation and glucuronidation. Major circulating metabolites included 3-hydroxy-desloratadine glucuonide (3-OH-DL-Glu), dihydroxy-DL-glucuronides, and several metabolites resulting from descarboethoxylation and oxidation of the piperidine ring. LOR was completely metabolized by 6 h post-dose. LOR-derived radiocarbon was excreted almost equally in the urine (41%) and feces (43%). About 13% of the dose was eliminated in the urine as 3-OH-DL-Glu. DL accounted for less than 2% of the dose recovered in the urine and only trace amounts of LOR were detected. 3-OH-DL was the major fecal metabolite ( approximately 17% of the dose). The combined amount of 5- and 6-hydroxy-DL contributed to an additional 10.7% of the dose in feces. Approximately 5.4% and 2.7% of the dose were excreted in the feces as unchanged drug and DL, respectively.

A review of the role of levocetirizine as an effective therapy for allergic disease

BACKGROUND

Levocetirizine is the R-enantiomer of cetirizine dihydrochloride with pharmacodynamically and pharmacokinetically favourable characteristics.

OBJECTIVE

To review the evidence that levocetirizine is an effective therapy for allergic disease.

METHODOLOGY

Relevant articles in English or with English abstracts were identified from systematic PubMed searches.

RESULTS

Levocetirizine has high bioavailability, high affinity for and occupancy of the H1 receptor, rapid onset of action, limited distribution and minimal hepatic metabolism. Clinical trials indicate that it is safe and effective for the treatment of allergic rhinitis and chronic idiopathic urticaria in adults and children with a minimal number of untoward effects. It is also becoming clearer that, in addition to its being a potent antihistamine, levocetirizine has several anti-inflammatory effects that are observed at clinically relevant concentrations that may enhance its therapeutic benefit. Furthermore, there appears to be a growing trend for the use of levocetirizine as long-term therapy in addition to it being used as a treatment for the immediate short-term manifestations of allergic disease.

CONCLUSION

Levocetirizine is an effective and safe treatment for use in adults and children with allergic disease.

Histamine directly and synergistically with lipopolysaccharide stimulates cyclooxygenase-2 expression and prostaglandin I(2) and E(2) production in human coronary artery endothelial cells

Although histamine plays an essential role in inflammation, its influence on cyclooxygenases (COX) and prostanoid homeostasis is not well understood. In this study, we investigated the effects of histamine on the expression of COX-1 and COX-2 and determined their contribution to the production of PGE(2), prostacyclin (PGI(2)), and thromboxane A(2) in human coronary artery endothelial cells (HCAEC). Incubation of HCAEC monolayers with histamine resulted in marked increases in the expression of COX-2 and production of PGI(2) and PGE(2) with no significant change in the expression of COX-1. Histamine-induced increases in PGI(2) and PGE(2) production were due to increased expression and function of COX-2 because gene silencing by small interfering RNA or inhibition of the catalytic activity by a COX-2 inhibitor blocked prostanoid production. The effects of histamine on COX-2 expression and prostanoid production were mediated through H(1) receptors. In addition to the direct effect, histamine was found to amplify LPS-stimulated COX-2 expression and PGE(2) and PGI(2) production. In contrast, histamine did not stimulate thromboxane A(2) production in resting or LPS-activated HCAEC. Histamine-induced increases in the production of PGE(2) and PGI(2) were associated with increased expression of mRNA encoding PGE(2) and PGI(2) synthases. The physiological role of histamine on the regulation of COX-2 expression in the vasculature is indicated by the findings that the expression of COX-2 mRNA, but not COX-1 mRNA, was markedly reduced in the aortic tissues of histidine decarboxylase null mice. Thus, histamine plays an important role in the regulation of COX-2 expression and prostanoid homeostasis in vascular endothelium.

In Vitro Pharmacology of Clinically Used Central Nervous System-Active Drugs as Inverse H1 Receptor Agonists

The human histamine H(1) receptor (H(1)R) is a prototypical G protein-coupled receptor and an important, well characterized target for the development of antagonists to treat allergic conditions. Many neuropsychiatric drugs are also known to potently antagonize this receptor, underlying aspects of their side effect profiles. We have used the cell-based receptor selection and amplification technology assay to further define the clinical pharmacology of the human H(1)R by evaluating >130 therapeutic and reference drugs for functional receptor activity. Based on this screen, we have reported on the identification of 8R-lisuride as a potent stereospecific partial H(1)R agonist (Mol Pharmacol 65:538-549, 2004). In contrast, herein we report on a large number of varied clinical and chemical classes of drugs that are active in the central nervous system that display potent H(1)R inverse agonist activity. Absolute and rank order of functional potency of these clinically relevant brain-penetrating drugs may possibly be used to predict aspects of their clinical profiles, including propensity for sedation.

Effect of azelastine, montelukast, and their combination on allergen-induced bronchoconstriction in asthma

OBJECTIVES

Histamine and cysteinyl leukotrienes play an important role in early (EAR) and late (LAR) allergen reactions. Although protection by anti-histamines and anti-leukotrienes has been studied extensively, little is known about the effect of their combination. We, therefore, assessed the effect of clinically recommended doses of azelastine and montelukast alone and in combination on EAR and LAR.

METHODS

Seventeen patients (mean age 31 years, 14 m/3 f) with asthma and proven EAR and LAR received an oral dose of 4 mg azelastine twice daily, or 10mg montelukast once daily, or both for 1 week, in a double-blind, double-dummy, cross-over fashion. FEV(1) was measured after single-dose allergen challenges during EAR (0-2h) and LAR (2-9h).

RESULTS

Azelastine, montelukast and their combination protected against both EAR and LAR (p<0.004, each) by 46% and 43%, 76% and 59%, and 89% and 78%, respectively. Azelastine was not as effective during EAR but equally effective to montelukast during LAR. The combination was superior to each drug alone during both EAR and LAR (p<0.05, each).

CONCLUSION

The combination of azelastine and montelukast in clinically recommended doses has a greater effect in suppressing early and late allergen reactions than each drug alone.

Antihistamines and their role as antipruritics

Antihistamines that bind to the histamine 1 receptor (H1) serve as important therapeutic agents to counter the effects of histamine in the skin. Two generations of antihistamines exist; however, second-generation agents are more advantageous because they cause less sedation, have a longer half life and are more selective for the H1 receptor. While H1 antihistamines have proven to be effective at reversing the pruritus and cutaneous lesions of chronic urticaria, their ability to treat pruritus associated with other cutaneous and systemic diseases is unproven.

A new antihistamine levocetirizine inhibits eosinophil adhesion to vascular cell adhesion molecule-1 under flow conditions

BACKGROUND

We previously demonstrated that low concentrations of a new antihistamine levocetirizine inhibited eosinophil transmigration through human microvascular endothelial cells.

OBJECTIVE

Here, the inhibitory effect of levocetirizine on eosinophil adhesion to recombinant human vascular cell adhesion molecule-1 (rhVCAM)-1 was examined under conditions of shear stress using an in vitro model of the post-capillary venules.

METHODS

Eosinophils isolated from normal subjects were pre-incubated with a concentration range of levocetirizine (10(-6)-10(-10) m) or negative dilution control. Resting or granulocyte macrophage-colony stimulating factor (GM-CSF)-stimulated cells were pumped through rhVCAM-1 (10 microg/mL) coated capillary tubes using a microfluidic syringe pump at a precise and constant flow rate (1 dyn/cm(2)). Images of rolling and firmly adherent eosinophils were captured using real-time video microscopy.

RESULTS

Levocetirizine significantly inhibited resting eosinophil adhesion to rhVCAM-1 with maximal effect at 10(-8) M with an EC(50) of 10(-9) m. Levocetirizine almost abolished resting eosinophil adhesion by the 15 min time-point. GM-CSF significantly enhanced eosinophil adhesion and their ability to flatten on rhVCAM-1. Both phenomena were inhibited by levocetirizine in a dose-dependent manner, at both 5 and 15 min (optimal concentration of 10(-8) m with an EC(50) of 10(-9) m). Real-time imaging revealed that the effect of levocetirizine on post-adhesion behaviour (detachment, flatness) contributed to its inhibitory action on eosinophil adhesion to rhVCAM-1. In contrast, very late antigen (VLA)-4 mAb inhibited eosinophil adhesion to rhVCAM-1 from the earliest time-points.

CONCLUSION

Physiologically relevant concentrations of levocetirizine inhibit resting and GM-CSF-stimulated firm eosinophil adhesion to rhVCAM-1 under flow conditions.

Comparison of the Risk of Drowsiness and Sedation between Levocetirizine and Desloratadine

BACKGROUND AND OBJECTIVES

Desloratadine and levocetirizine are histamine H(1) receptor antagonists (antihistamines) that were launched in the UK in 2001. Our objective was to compare the frequency with which drowsiness and sedation were reported for desloratadine and levocetirizine within the first 30 days of observation, as monitored using the observational cohort technique of prescription-event monitoring (PEM).

METHODS

Exposure data were derived from dispensed prescriptions written by primary care physicians and outcome data were derived from questionnaires that were posted to prescribers at least 6 months after the date of the first prescription for each patient. The odds ratio (OR) was calculated using unconditional logistic regression modelling. The effect of age, sex, reported prescribing indication (allergic rhinitis with asthma/wheezing, allergic rhinitis without asthma/wheezing, 'other'), pattern of use and reported previous antihistamine use on the OR was examined. A time-to-event analysis was performed.

RESULTS

The cohorts comprised >24,000 patients in total. Cohort demographics were similar (both cohorts: median age 37 years; 60% women); the most frequently reported prescribing indication for both drugs was allergic rhinitis without asthma/wheezing (54%). The incidence of first reports of drowsiness/sedation for levocetirizine or desloratadine was low (46 [0.37%] and 9 [0.08%], respectively) and statistically different (p < 0.0001). These events tended to occur earlier for desloratadine than levocetirizine (50% at 7 or 14 days of observation, respectively; p = 0.6487), but the cumulative time to event differed, with more events observed for levocetirizine than expected (p < 0.0001; 46 vs 28.09). The final estimates of risk were the sex-adjusted ORs for each prescribing indication category: allergic rhinitis with asthma/wheezing (3.51; 95% CI 0.71, 17.43; n = 3357), allergic rhinitis without asthma/wheezing (6.75; 95% CI 2.37, 19.22; n = 12,627) and 'other' (3.11; 95% CI 0.86, 11.31; n = 6725).

DISCUSSION

Although the reporting rates of drowsiness and sedation are low for both drugs, patients prescribed levocetirizine are more likely to experience drowsiness and sedation in the first month of observation (after starting treatment) than patients prescribed desloratadine. For patients with allergic rhinitis without asthma/wheezing, the sex-adjusted odds of drowsiness/sedation were over six times greater in patients using levocetirizine than desloratadine in the first month of observation, with the OR being statistically significant. For the other two indication categories, allergic rhinitis with asthma/wheezing and 'other', the OR was not statistically significant.

CONCLUSIONS

Although the risk of drowsiness/sedation is low, conditions such as allergic rhinitis are common, which makes any impact on patient cognitive function important. Doctors should be aware of this when prescribing these products to patients where daytime sedation is undesirable. However, essential components of the comparative benefit-risk evaluation of these two products include assessment of efficacy and patient preference (neither of which forms part of this study).

Once-daily fexofenadine treatment for chronic idiopathic urticaria: a multicenter, randomized, double-blind, placebo-controlled study

BACKGROUND

Chronic idiopathic urticaria (CIU) can have a profound effect on patients' health and quality of life.

OBJECTIVE

To evaluate the efficacy and safety of once-daily dosing of fexofenadine hydrochloride, 180 mg, on CIU.

METHODS

This randomized, double-blind, parallel-group, placebo-controlled study consisted of a placebo run-in period followed by a 4-week treatment period. Patients 12 years and older with active CIU were randomized 2:1 to receive once-daily fexofenadine, 180 mg, or placebo. The primary end points were change from baseline in mean daily number of wheals (MNW score) and mean daily severity of pruritus during treatment. Secondary efficacy measures included modified total symptom scores and MNW and pruritus severity scores evaluated weekly and instantaneously at trough drug levels.

RESULTS

Patients administered fexofenadine (n = 163) experienced significantly greater improvements in MNW and pruritus severity scores compared with the placebo group (n = 92) (P < .001 for both). Similarly, throughout treatment and at each individual week, the mean reductions in modified total symptom scores were significantly greater in the fexofenadine group (P < or = .005 for all comparisons vs placebo). The mean reductions in instantaneous MNW and pruritus severity scores were greater in patients in the fexofenadine group than in those who received placebo (MNW score: P = .015; pruritus severity score: P < .001). There were no significant differences in the frequency of treatment-emergent adverse events between the 2 treatment groups.

CONCLUSIONS

A once-daily dose of fexofenadine hydrochloride, 180 mg, offered effective, well-tolerated relief for the management of CIU.

Second-generation antihistamines in asthma therapy: is there a protective effect?

Second-generation histamine H(1) receptor antagonists are recognized as being highly effective treatments for allergic-based disease and are among the most frequently prescribed drugs in the world. The newer antihistamines represent a heterogeneous group of compounds with markedly different chemical structures, a spectrum of antihistaminic properties, adverse effects, half-life, tissue distribution, metabolism and varying degrees of anti-inflammatory effects. Histamine is an important mast cell- and basophil-derived mediator that has been implicated in the pathogenesis of asthma, resulting in smooth muscle contraction, mucus hypersecretion, and increased vascular permeability leading to mucosal edema. Antihistamines should never be used as monotherapy for asthma but there is evidence that these drugs give a measure of protection in histamine-induced bronchoconstriction. Furthermore, several studies have demonstrated that the use of second-generation antihistamines, as adjunct therapy, may benefit those patients whose allergic asthma co-exists with allergic rhinitis. Indeed, many patients present with both allergic rhinitis and asthma. The link between the upper and lower respiratory airways is now well established and there is increasing evidence that allergic rhinitis is a risk factor for the development of asthma. More recently, a number of novel antihistamines have been developed which are either metabolites of active drugs or enantiomers and there is emerging evidence that at least one of these drugs, desloratadine, may give significant symptomatic benefit in some types of asthma. It is of interest to note that cetirizine provides a primary pharmacological intervention strategy to prevent the development of asthma in specifically-sensitized high risk groups of infants. Moreover, the documented anti-inflammatory activities of antihistamines may provide a novel mechanism of action for the therapeutic control of virus-induced asthma exacerbations by inhibiting the expression of intercellular adhesion molecule-1 (ICAM-1) by airway epithelial cells. Finally, several well-conducted studies suggest that combination therapy with antihistamines and antileukotrienes may be as effective as corticosteroid use in patients with allergic asthma and seasonal allergic rhinitis.

Role of histamine and platelet-activating factor in allergic rhinitis

This review is focused on the effects of histamine and platelet-activating factor (PAF) in allergic rhinitis and the plausible implications for therapy. Rhinitis is defined as a heterogeneous disorder resulting from an IgE-mediated reaction associated with nasal inflammation of variable intensity. Two phases of response are triggered by an IgE/allergen cross-linking event: the first is the release of preformed mediators such as histamine or interleukins from mast cells and basophils; the second begins when cells start producing lipid-derived mediators. One of these mediators is PAF. Apart from leukotrienes, PAF is perhaps the most potent inflammatory mediator in allergic rhinitis for inducing vascular leakage, a response that may contribute to the appearance of rhinorrhea and nasal congestion.

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.

QT Correction Methods in Children and Adolescents

INTRODUCTION

Accurate determination of the QTc interval has become increasingly important in the assessment of a drug's ability to prolong cardiac repolarization. Previous work suggests the most appropriate correction formula for adults is QTc=QT/RR0.40, but little on correction methods for children and adolescents has been published.

METHODS AND RESULTS

In this study, ECG data were obtained from a meta-analysis of seven clinical trials for attention deficit/hyperactivity disorder (ADHD) involving 2,288 children and adolescents. The most appropriate formula for children and adolescents included in this database was found to be QTc=QT/RR0.38. Adjustments of the correction factor specifically for males and females of different ages also are reported.

CONCLUSION

QT correction methods developed for adults do not apply to children. As accurate QTc determination plays a larger role in assessing a drug's potential to retard repolarization, use of age- and gender-specific correction formulas becomes more important.

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.

Histamine induces Toll-like receptor 2 and 4 expression in endothelial cells and enhances sensitivity to Gram-positive and Gram-negative bacterial cell wall components

Histamine is a major inflammatory molecule released from the mast cell, and is known to activate endothelial cells. However, its ability to modulate endothelial responses to bacterial products has not been evaluated. In this study we determined the ability of histamine to modulate inflammatory responses of endothelial cells to Gram-negative and Gram-positive bacterial cell wall components and assessed the role of Toll-like receptors (TLR) 2 and 4 in the co-operation between histamine and bacterial pathogens. Human umbilical vein endothelial cells (HUVEC) were incubated with lipopolysaccharide (LPS), lipoteichoic acid (LTA), or peptidoglycan (PGN) in the presence or absence of histamine, and the expression and release of interleukin-6 (IL-6), and NF-kappaB translocation were determined. The effect of histamine on the expression of mRNA and proteins for TLR2 and TLR4 was also evaluated. Incubation of HUVEC with LPS, LTA and PGN resulted in marked enhancement of IL-6 mRNA expression and IL-6 secretion. Histamine alone markedly enhanced IL-6 mRNA expression in HUVEC, but it did not stimulate proportional IL-6 release. When HUVEC were incubated with LPS, LTA, or PGN in the presence of histamine marked amplification of both IL-6 production and mRNA expression was noted. HUVEC constitutively expressed TLR2 and TLR4 mRNA and proteins, and these were further enhanced by histamine. The expression of mRNAs encoding MD-2 and MyD88, the accessory molecules associated with TLR signalling, were unchanged by histamine treatment. These results demonstrate that histamine up-regulates the expression of TLR2 and TLR4 and amplifies endothelial cell inflammatory responses to Gram-negative and Gram-positive bacterial components.

Arthropod-derived histamine-binding protein prevents murine allergic asthma

Because histamine receptor type I blockade attenuates allergic asthma, we asked whether complete neutralization of histamine by an arthropod-derived, high affinity histamine-binding protein (EV131) would prevent allergic asthma. Intranasal administration of EV131 given before Ag challenge in immunized mice prevented airway hyperreactivity by 70%, and abrogated peribronchial inflammation, pulmonary eosinophilia, mucus hypersecretion, and IL-4 and IL-5 secretion. Saturation with histamine abrogated the inhibitory effect of EV131 on bronchial hyperreactivity. The inhibitory effect of EV131 on bronchial hyperreactivity was comparable to that of glucocorticosteroids. These results demonstrate that histamine is a critical mediator of allergic asthma. Therefore, complete neutralization of histamine, rather than specific histamine receptor blockade, may have a profound effect on allergic asthma.

Levocetirizine improves nasal obstruction and modulates cytokine pattern in patients with seasonal allergic rhinitis: a pilot study

BACKGROUND

Allergic rhinitis is characterized by an IgE-dependent inflammation. Nasal obstruction is related to allergic inflammation. Some antihistamines have been demonstrated to be capable of improving this nasal symptom.

OBJECTIVE

The aim of this pilot study was to evaluate nasal symptoms, nasal airflow, inflammatory cells, and cytokine pattern in patients with seasonal allergic rhinitis (SAR), before and after treatment with levocetirizine, desloratadine, or placebo.

METHODS

Thirty patients with SAR were evaluated, 27 males and three females (mean age 26.9+/-5.4 years). All of them received levocetirizine (5 mg/day), desloratadine (5 mg/day), or placebo for 2 weeks. The study was double-blind, parallel-group, placebo-controlled, and randomized. Total symptom score (TSS) (including: rhinorrhea, nasal itching, sneezing, and nasal obstruction) was assessed before and after treatment. Rhinomanometry, nasal lavage, and nasal scraping were performed in all subjects before and after treatment. Inflammatory cells were counted by conventional staining; IL-4 and IL-8 were measured by immunoassay on fluids recovered from nasal lavage.

RESULTS

Levocetirizine treatment induced significant symptom relief (P=0.0009) and improved nasal airflow (P=0.038). Desloratadine also relieved TSS (P=0.01), but did not affect nasal airflow. Levocetirizine significantly reduced eosinophils (P=0.029), neutrophils (P=0.005), IL-4 (P=0.041), and IL-8 (P=0.02), whereas desloratadine diminished IL-4 only (P=0.044). Placebo treatment did not significantly affect any evaluated parameters.

CONCLUSIONS

This pilot study demonstrates the effectiveness of levocetirizine in: (i) relieving nasal symptoms, (ii) improving nasal airflow, (iii) reducing leucocyte infiltration, and (iv) diminishing cytokine levels. These findings are the first evidence of the effectiveness of levocetirizine in SAR.

Comparative activity of cetirizine and desloratadine on histamine-induced wheal-and-flare responses during 24 hours

BACKGROUND

Cetirizine and desloratadine are antihistamines active in the treatment of symptoms associated with seasonal allergic rhinitis and chronic urticaria.

OBJECTIVE

To compare the antihistamine activity of desloratadine, the active metabolite of loratadine, with that of cetirizine in the skin wheal-and-flare responses during 24 hours.

METHODS

This was a double-blind, randomized, placebo-controlled, single oral dose, crossover study. Skin reaction to histamine (100 mg/mL), administered by prick tests, was measured by the wheal and flare surface areas for 24 hours (before treatment and at 0.5, 1, 2, 3, 4, 6, 8, 10, 12, and 24 hours). Eighteen healthy volunteers (mean age, 33.9 years; 13 women) participated in this study. The areas under the curves of the wheal-and-flare responses as a function of time (primary efficacy variables) were compared using analysis of variance.

RESULTS

A highly significant overall treatment effect (P < .001) was detected for wheal and flare inhibition, with the activity of cetirizine and desloratadine significantly superior to that of placebo (P < .001). In addition, the activity of cetirizine was significantly superior to that of desloratadine (P < .001). With desloratadine, only 3 of the 18 subjects achieved a wheal inhibition of at least 70%, occurring between 2 and 4 hours, whereas all subjects using cetirizine reached a wheal inhibition of at least 70% between 0.5 and 3 hours (median time, 1.7 hours). The difference between the 2 active drugs was highly significant (P < .001). The median duration of wheal inhibition of at least 70% was zero with placebo and desloratadine and was 21.9 hours with cetirizine (P < .001). No serious adverse events were reported, and no subject withdrew from the study due to an adverse event.

CONCLUSION

Cetirizine was associated with significantly greater suppression of skin reactivity to histamine compared with desloratadine during 24 hours after a single dose, with a consistent duration of action for cetirizine, as previously reported.

Treatment of nonallergic perennial rhinitis

Nonallergic perennial rhinitis (also commonly referred to as vasomotor rhinitis) is a chronic non-IgE-mediated condition that is characterized by symptoms which are similar to those seen in allergic rhinitis, but which persist for over nine months each year. Although treatment of vasomotor rhinitis involves the use of either intranasal corticosteroids or antihistamines, the corticosteroids are generally not effective in treatment of all the symptoms of vasomotor rhinitis and have generally been shown to be effective in patients with eosinophilia. With the exception of azelastine, the only topical antihistamine to be approved by the FDA for the treatment of nonallergic rhinitis, the antihistamines have also produced inconsistent results. While clinical studies of azelastine have demonstrated that this drug is highly efficacious in the treatment of all the symptoms of vasomotor rhinitis, mechanistic studies have demonstrated that azelastine has potent anti-inflammatory effects (in particular attenuation of the expression and synthesis of pro-inflammatory cytokines, leukotrienes, and cell adhesion molecules), which are likely to contribute to its clinical efficacy. Furthermore, pharamacokinetic studies have suggested that since azelastine has a more rapid onset of action, compared to most other antihistamines and intranasal corticosteroids, then azelastine nasal spray may be considered as primary therapy for patients with symptoms of both allergic and/or vasomotor (nonallergic perennial) rhinitis.

Levocetirizine better protects than desloratadine in a nasal provocation with allergen

BACKGROUND

Direct comparisons of antihistamines are rare but very much needed. Newly available antihistamine preparations, levocetirizine, the R-enantiomer of racemate cetirizine, and desloratadine, an active metabolite of loratadine, have been recently released for allergic rhinitis.

OBJECTIVE

We sought to compare levocetirizine and desloratadine in a nasal provocation test (NPT) with grass pollen.

METHODS

Twenty-four volunteers with grass pollen allergy and a history of rhinitis were enrolled in a double-blind, placebo-controlled, crossover study. Three NPTs were performed in a dose-escalating manner during the out-of-season period 4 hours after a single dose of levocetirizine (5 mg), desloratadine (5 mg), or placebo.

RESULTS

CONCLUSIONS

This study demonstrates a better overall protection of a single dose of levocetirizine compared with desloratadine in an NPT with grass pollen allergen. In contrast to late-phase inflammatory markers, which were unaffected, extravascular leakage of the early-phase marker albumin was significantly limited by levocetirizine.

Fexofenadine hydrochloride, 180 mg, exhibits equivalent efficacy to cetirizine, 10 mg, with less drowsiness in patients with moderate-to-severe seasonal allergic rhinitis

BACKGROUND

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

OBJECTIVE

To compare the effects of fexofenadine hydrochloride, 180 mg, and cetirizine, 10 mg, on symptoms, drowsiness, and motivation in patients with moderate-to-severe SAR.

METHODS

In this 2-week multicenter, double-blind, randomized study, 495 subjects with moderate-to-severe SAR received once-daily fexofenadine hydrochloride, 180 mg, or cetirizine, 10 mg, without regard to food intake. Daily 12-hour reflective (AM, PM) and instantaneous (AM) individual symptoms and total symptom score (TSS) were evaluated. Drowsiness and motivation were recorded daily using visual analog scale at 7 AM, 10 AM, and 3 PM.

RESULTS

Between-treatment differences in reduction from baseline in AM instantaneous and 24-hour reflective TSS were -0.18 [95% confidence interval (CI), -0.55 to 0.20) and -0.22 (95% CI, -0.59 to 0.15), respectively. Since CIs for reduction in TSS between treatments fell within a 0.7 margin (defined a priori), treatments were considered statistically equivalent. Patients receiving fexofenadine experienced significantly less overall drowsiness vs baseline than those receiving cetirizine [-2.33 (95% CI, -3.80 to 0.86) vs 0.37 (95% CI, -1.10 to 1.84), P = .0110]. There was a trend toward greater improvements in overall motivation with fexofenadine compared with cetirizine [-2.36 (95% CI, -3.83 to 0.90) vs -0.30 (95% CI, -1.76 to 1.17), P = .0504].

CONCLUSIONS

Once-daily fexofenadine hydrochloride, 180 mg, given for 2 weeks caused statistically and clinically equivalent improvement in symptoms and significantly less drowsiness va baseline, compared with cetirizine, 10 mg, in patients with moderate-to-severe SAR.

Compared pharmacological characteristics in humans of racemic cetirizine and levocetirizine, two histamine H1-receptor antagonists

The potent histamine H(1)-receptor antagonist cetirizine (Zyrtec) is a racemic mixture of levocetirizine (now available under the trademark Xyzal and dextrocetirizine. In this Commentary, we examine some biological properties of cetirizine and levocetirizine, namely enantioselectivity in pharmacological activity and pharmacokinetic properties, with emphasis on the possibility of racemization, the compared behavior of the two enantiomers, and the potential for interactions with other drugs. Recent data demonstrate that the antihistaminergic activity of the racemate is primarily due to levocetirizine. Levocetirizine is rapidly and extensively absorbed, poorly metabolized, and not subject to racemization. Its pharmacokinetic characteristics are comparable after administration alone or in the racemate. Its apparent volume of distribution is smaller than that of dextrocetirizine (0.41 L kg(-1) vs. 0.60 L kg(-1)). Moreover, the non-renal (mostly hepatic) clearance of levocetirizine is also significantly lower than that of dextrocetirizine (11.8 mL min(-1) vs. 29.2 mL min(-1)). Our conclusion is that levocetirizine is indeed the eutomer of cetirizine. The evidence reviewed here confirms preclinical findings and offers a rationale for the chiral switch from the racemate to levocetirizine.

Relative potency of fexofenadine HCl 180 mg, loratadine 10 mg, and placebo using a skin test model of wheal-and-flare suppression

BACKGROUND

H1-receptor antagonists differ in their ability to produce peripheral H1-blockade. Suppression of histamine-induced flares and wheals is a useful objective test for measuring these differences.

OBJECTIVE

To evaluate the relative potency of fexofenadine HCI 180 mg, loratadine 10 mg, and placebo (PBO) in suppressing histamine-induced flares and wheals and compare the onset, duration, and maximum suppression of histamine achieved with each agent.

METHODS

Thirty healthy volunteers were enrolled in this randomized, double-blind, single-dose, crossover study. Flares and wheals induced by skin-prick testing with histamine 1.8 mg/mL were measured before treatment, every 20 minutes during the first hour after dosing, and thereafter hourly between 2 and 12 hours and between 23 and 25 hours postdose.

RESULTS

Fexofenadine was significantly more effective than loratadine in suppressing the histamine-induced flare response at hours 2 through 7 and 10 through 12 and produced greater flare suppression than did PBO at hours 2 through 25. Onset of flare suppression occurred 2 hours after dosing with fexofenadine and 4 hours after dosing with loratadine. Likewise, fexofenadine was superior to loratadine in suppressing the wheal response from hours 1 through 12 and was more effective than PBO at hours 1 through 12, 24, and 25. Throughout the 25-hour measurement interval, the magnitude of difference in both wheal and flare suppression consistently favored fexofenadine over loratadine.

CONCLUSIONS

In a skin test model of wheal-and-flare suppression, fexofenadine showed rapid distribution into the skin compartment with faster onset of action and greater potency vs loratadine.