Potent Histamine H3 Receptor Antagonist Research Articles

Discovery of New Highly Potent Histamine H3 Receptor Antagonists, Calcium Channel Blockers, and Acetylcholinesterase Inhibitors.

At present, one of the most promising strategies to tackle the complex challenges posed by Alzheimer's disease (AD) involves the development of novel multitarget-directed ligands (MTDLs). To this end, we designed and synthesized nine new MTDLs using a straightforward and cost-efficient one-pot Biginelli three-component reaction. Among these newly developed compounds, one particular small molecule, named 3e has emerged as a promising MTDL. This compound effectively targets critical biological factors associated with AD, including the simultaneous inhibition of cholinesterases (ChEs), selective antagonism of H3 receptors, and blocking voltage-gated calcium channels. Additionally, compound 3e exhibited remarkable neuroprotective activity against H2O2 and Aβ1-40, and effectively restored cognitive function in AD mice treated with scopolamine in the novel object recognition task, confirming that this compound could provide a novel and innovative therapeutic approach for the effective treatment of AD.

Drug–drug interaction potential and clinical pharmacokinetics of enerisant, a novel potent and selective histamine H3 receptor antagonist

We evaluated the in vitro drug–drug interaction (DDI) potential of enerisant (TS-091), a histamine H3 receptor antagonist/inverse agonist, mediated by cytochrome P450 (CYP) and transporters, as well as the pharmacokinetics of enerisant in healthy male subjects. Enerisant did not inhibit CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, or CYP3A4 and did not induce CYP1A2, CYP2B6, or CYP3A4. Enerisant inhibited organic cation transporter 2, multidrug and toxin extrusion protein (MATE) 1, and MATE2-K, but not P-glycoprotein (P-gp), breast cancer resistance protein, organic anion transporting polypeptide (OATP) 1B1, OATP1B3, organic anion transporter (OAT) 1, or OAT3. Enerisant was a substrate for P-gp, but not for eight other transporters. In healthy male subjects, enerisant was rapidly absorbed after oral administration, and the plasma concentration increased dose-dependently. The urinary excretion of enerisant within 48 h after administration was 64.5% to 89.9% of the dose, indicating that most of the absorbed enerisant was excreted in the urine without being metabolized. Based on the plasma concentrations at the estimated clinical dose, enerisant is unlikely to cause CYP-mediated, clinically relevant DDI. Although the possibility of transporter-mediated, clinically relevant DDI cannot be ruled out, there is little or no risk of side effects.

Pharmacokinetics and Dose Proportionality of Betahistine in Healthy Individuals

Betahistine dihydrochloride is widely used to reduce the severity and frequency of vertigo attacks associated with Ménière’s disease. Betahistine is an analogue of histamine, and is a weak histamine H1 receptor agonist and potent histamine H3 receptor antagonist. The recommended therapeutic dose for adults ranges from 24 to 48 mg given in doses divided throughout the day. Betahistine undergoes extensive first-pass metabolism to the major inactive metabolite 2-pyridyl acetic acid (2PAA), which can be considered a surrogate index for quantitation of the parent drug due to extremely low plasma levels of betahistine. The aim of the present investigation was to assess the pharmacokinetics and dose proportionality of betahistine in Arabic healthy adult male subjects under fasting conditions. A single dose of betahistine in the form of a 8, 16, or 24 mg tablet was administered to 36 subjects in randomized, cross-over, three-period, three-sequence design separated by a one week washout period between dosing. The pharmacokinetic parameters Cmax, AUC0–t, AUC0–∞, Tmax, and Thalf were calculated for each subject from concentrations of 2-PAA in plasma, applying non-compartmental analysis. The current study demonstrated that betahistine showed linear pharmacokinetics (dose proportionality) in an Arabic population over the investigated therapeutic dose range of 8–24 mg.

Coumarins from the roots of Angelica dahurica cause anti-allergic inflammation.

Allergic inflammation is induced by allergens and leads to various allergic diseases, including rhinitis, asthma and conjunctivitis. Histamine is important in the pathogenesis of an immunoglobulin E-dependent allergic reaction and results in the secretion of cytokines associated with inflammation. Angelica dahurica (A. dahurica) is a medicinal plant widely used in China for the treatment of symptoms related to allergic inflammation. The present study investigated the chemical constituents from A. dahurica and evaluated their reductive effect on allergic inflammation. As a result, 15 compounds including 13 coumarins have been identified as isoimperatorin (1), imperatorin (2), oxypeucedanin (3), oxypeucedanin hydrate (4), bergapten (5), byakangelicin (6), phellopterin (7), byakangelicol (8), isopimpinellin (9), xanthotoxol (10), xanthotoxin (11), pimpinellin (12), scopoletin (13), β-sitosterol (14) and daucosterol (15). Compounds 1-13 were able to reduce the release of histamine, with compounds 4-6 exhibiting the most potent activity. Furthermore, compounds 1-12 were able to inhibit the secretion of tumor necrosis factor-α, interleukin (IL)-1β and IL-4, with compounds 5 and 7 exhibiting the strongest inhibitory effects. These compounds implemented the inhibitory effects on the expression of inflammatory cytokine genes through the inhibition of nuclear factor-κB activation. Virtual screening by a docking program indicated that compound 3 is a potent histamine H1 receptor antagonist. Additionally, the calculated physicochemical properties of these compounds support most furanocoumarins to be delivered to binding sites and permeate the cell membrane. The present findings contribute to understanding how A. dahurica attenuates allergic inflammation.

Screening of process variables to enhance the solubility of famotidine with 2-HydroxyPropyl–β-Cyclodextrin & PVP K-30 by using Plackett–Burman design approach

In the present work, inclusion complex of famotidine (FMT) was prepared with (2-HydroxyPropyl)–β-Cyclodextrin (HP-β-CyD) and polyvinylpyrrolidone K-30 (PVP K-30) by spray drying technique to enhance the solubility of famotidine. FMT is a potent histamine H2-receptor antagonist having low solubility as well as oral bioavailability. In order to enhance the solubility of FMT, a quality by design (QbD) approach has been used by employing Plackett–Burman design (PBD). With the application of PBD, seven independent process variables were investigated and optimized for maximum solubility. The developed inclusion complex was characterized for solubility, encapsulation efficiency, FTIR, FESEM, XRD. In-vitro drug release study was also performed by preparing fast dissolving tablets of inclusion complex. Solubility of FMT in prepared complex was found 38 fold higher than pure FMT while %EE was found 92.10%. Statistical analysis of the data (ANOVA) indicates an adequate model fitting predicting the effect of process parameters affecting the solubility. In conclusion, spray dried inclusion complex can effectively increases the solubility as well as dissolution rate of the FMT and other active pharmaceutical ingredients in combination of the fast dissolving tablets.

Desloratadine citrate disodium injection, a potent histamine H1 receptor antagonist, inhibits chemokine production in ovalbumin-induced allergic rhinitis guinea pig model and histamine-induced human nasal epithelial cells via inhibiting the ERK1/2 and NF-kappa B signal cascades

Chemokines have chemotactic properties on leukocyte subsets whose modulation plays a pivotal role in allergic inflammatory processes. Our present study was designed to investigate the anti-allergic and anti-inflammatory properties of desloratadine citrate disodium injection (DLC) and elucidate the molecular mechanisms of its anti-inflammatory properties. The anti-allergic effects of DLC were evaluated based on allergic symptoms, serological marker production and histological changes of the nasal mucosa in guinea pigs model of allergic rhinitis. The anti-inflammatory properties and molecular mechanisms of DLC were explored by studying the regulation of a set of chemokines and extracellular signal-regulated kinase (ERK)1/2 and nuclear factor-kappa B (NF-κB) pathways, after DLC treatment in guinea pigs model of allergic rhinitis in vivo and histamine-activated human nasal epithelial cells (HNECs) in vitro. In vivo model in guinea pigs, DLC alleviated the rhinitis symptoms, inhibited inflammatory cells infiltration in nasal lavage fluid (NLF) and histamine, monocyte chemotactic protein (MCP)-1, regulated on activation normal T cell expressed, and presumably secreted (RANTEs) and interleukin (IL)-8 release in sera and P-ERK1/2 and NF-κB activation in nasal mucosa. In vitro, DLC markedly inhibited histamine-induced production of MCP-1, RANTEs and IL-8 and suppressed c-Raf, mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) and ERK1/2 activation in HNECs. These results provide evidence that DLC possesses potent anti-allergic and anti-inflammatory properties. The mechanism of action underlying DLC in allergic inflammation appears to be inhibition of the phosphorylation of ERK1/2, in addition to blocking of the NF-κB pathway.

The effect of MP29‐02* is mediated via bitter taste receptors (TAS2R)

Background Dymista (MP29-02*) is a novel intranasal formulation of azelastine hydrochloride (AZE) and fluticasone propionate (FP) in an advanced delivery system with a welldocumented effect on allergic rhinitis. Its somewhat bitter taste is probably derived from AZE, a potent histamineH1-receptor antagonist. The taste is sometimes looked upon as a disadvantage. However, it might be that AZE induces some of its beneficial effect through activation of bitter taste receptors. Recent evidence indicates that bitter taste receptors are present in human upper airway mucosa in regions associated with high airflow and particulate deposition. Consequently the MP29-02* effects might be due not only to its anti-histaminic, mast-cell stabilizing, anti-leukotriene, and anti-inflammatory properties but also as due to activation of bitter taste receptors.

Efficient Synthesis of N-[4-(4-Chlorophenyl)butyl]-S-(3-piperidinopropyl)isothiourea (OUP-186) and Its Analogues Using 2-Nitrophenylacetyl Isothiocyanate: Application to Novel Histamine H3R Antagonists

A potent histamine H3 receptor antagonist OUP-186 with an S-alkyl-N-alkylisothiourea structure was synthesized using 3-phenylpropanoyl isothiocyanate (PPI) as an SCN source. The synthetic route was significantly improved by replacing 3-phenylpropanoyl isothiocyanate with 2-nitrophenylacetyl isothiocyanate (NPAI), giving a 74% overall yield in three steps from 4-(4-chlorophenyl)butylamine. In addition, the 2-nitrophenylacetyl isothiocyanate method successfully yielded two fluorine-containing analogues, and a shorter, C2 homologue of OUP-186.

Anti-allergic and anti-inflammatory properties of a potent histamine H1 receptor antagonist, desloratadine citrate disodium injection, and its anti-inflammatory mechanism on EA.hy926 endothelial cells

The present study, demonstrates that, desloratadine citrate disodium injection (DLC) possesses antihistaminic, anti-allergic and anti-inflammatory properties and elucidates its molecular mechanisms of anti-inflammatory properties. In vitro antihistamine activity of DLC was determined in guinea pig isolated tissues. In vivo antihistamine effects were evaluated after following intravenous administration of DLC in mice with histamine- induced paw edema and in rats with increased capillary permeability. Anti-allergic effects were assessed through passive cutaneous anaphylactic (PCA) reactions in sensitized rodents and ovalbumin-induced allergic rhinitis in rats. Anti-inflammatory properties and molecular mechanisms of DLC were determined on histamine- and lipopolysaccharide (LPS)—induced EA.hy926 endothelial cells. DLC exhibited significant and reversible inhibition of histamine-induced contractions of isolated guinea pig ileum with pA2 value of 8.88. Histamine-induced paw edema and increased capillary permeability were notably inhibited by DLC intravenous administration. In the model of PCA reactions, DLC showed significant activity in a dose-dependent nd potently inhibited both the early-phase and late-phase allergic reaction of ovalbumin-induced allergic rhinitis in rats. DLC alleviated the rhinitis symptoms and inhibited inflammatory cell infiltration, IL-4 and protein leakage in nasal lavage fluid (NLF). In EA.hy926 cells, DLC significantly inhibited the histamine- and LPS- induced IL-6 and IL-8 production and P-selectin and intercellular cell adhesion molecule-1 (ICAM-1) expression. Moreover, DLC reduced translocation of nuclear factor-kappaB (NF-κB) to the nucleus in activated EA.hy926 cells. These results provide evidence that DLC possesses potent antihistaminic, anti-allergic and, anti-inflammatory properties via suppressing IL-6, IL-8, P-selectin and ICAM-1 expression.

Discovery of aryl ureas and aryl amides as potent and selective histamine H3 receptor antagonists for the treatment of obesity (Part I)

A series of structurally novel aryl ureas was derived from optimization of the HTS lead as selective histamine H3 receptor (H3R) antagonists. The SAR was explored and the data obtained set up the starting point and foundation for further optimization. The most potent tool compounds, as exemplified by compounds 2l, 5b, 5d, and 5e, displayed antagonism potencies in the subnanomolar range in in vitro human-H3R FLIPR assays and rhesus monkey H3R binding assays.

Novel and highly potent histamine H3 receptor ligands. Part 3: An alcohol function to improve the pharmacokinetic profile

Synthesis and biological evaluation of potent histamine H3 receptor antagonists incorporating a hydroxyl function are described. Compounds in this series exhibited nanomolar binding affinities for human receptor, illustrating a new possible component for the H3 pharmacophore. As demonstrated with compound BP1.4160 (cyclohexanol 19), the introduction of an alcohol function counter-intuitively allowed to reach high in vivo efficiency and favorable pharmacokinetic profile with reduced half-life.

Effects of thioperamide on seizure development and memory impairment induced by pentylenetetrazole-kindling epilepsy in rats

Background Histamine H3 receptor antagonists have been considered as potential drugs to treat central nervous system diseases. However, whether these drugs can inhibit epileptogenesis remains unclear. This study aimed to investigate the effects of thioperamide, a selective and potent histamine H3 receptor antagonist, on the seizure development and memory impairment induced by pentylenetetrazole (PTZ)-kindling epilepsy in rats. Methods Chemical kindling was elicited by repeated intraperitoneal (ip) injections of a subconvulsant dose of PTZ (35 mg/kg) once every 48 hours for 12 times, and seizure activity of kindling was recorded for 30 minutes. Control rats were ip injected with saline instead of PTZ. Morris water maze was used to evaluate the spatial memory. Phosphorylated cyclic adenosine monophosphate response element binding protein (p-CREB) was tested by Western blotting in hippocampus. Results Intracerebroventricular (icv) injections with thioperamide (10 μg, 20 μg) 30 minutes before every PTZ injections, significantly prolonged the onset of PTZ-kindling and inhibited the seizure stages. PTZ-kindling seizures led to the impairment of spatial memory in rats, and thioperamide ameliorated the impairment of spatial learning and memory. Compared to non-kindling rats, there was a significant decrease in p-CREB level in hippocampus of the PTZ-kindling rats, which was reversed by thioperamide. Conclusions Thioperamide plays a protective role in seizure development and cognitive impairment of PTZ-induced kindling in rats. The protection of thioperamide in cognitive impairment is possibly associated with the enhancement of CREB-dependent transcription.

P2-444: A novel potent histamine H3 receptor antagonist produces discrete changes in brain activity during learning and episodic memory: Implications for cognitive enhancement

P2-444: A novel potent histamine H3 receptor antagonist produces discrete changes in brain activity during learning and episodic memory: Implications for cognitive enhancement

1-(3-{4-[(2,4-Dinitroanilino)methyl]phenoxy}propyl)piperidinium chloride

The title compound, C21H27N4O5+·Cl−, is one of the parent compounds for a recently developed series of novel potent histamine H3 receptor antagonists having additional fluorescent properties. The crystal structure is composed of discrete cations and anions connected by classical N—H⋯O and N—H⋯Cl hydrogen bonds. The crystal packing is further stabilized by weak C—H⋯Cl and C—H⋯O contacts.

Molecular mechanisms of G0/G1 cell-cycle arrest and apoptosis induced by terfenadine in human cancer cells.

Terfenadine (TF), a highly potent histamine H1 receptor antagonist, has been shown to exert no significant central nervous system side effects in clinically effective doses. In this study, we demonstrated that TF induced significant growth inhibition of human cancer cells, including Hep G2, HT 29, and COLO 205 cells, through induction of G(0)/G(1) phase cell-cycle arrest. The minimal dose of TF induced significant G(0)/G(1) arrest in these cells was 1-3 microM. The protein levels of p53, p21/Cip1, and p27/Kip1 were significantly elevated, whereas the kinase activities of cyclin-dependent kinase 2 (CDK2) and CDK4 were inhibited simultaneously in the TF-treated cells. On the other hand, significant apoptosis, but not G(0)/G(1) arrest, was induced in the HL 60 (p53-null) or Hep 3B (with deleted p53) cells when treated with TF (3-5 microM). To clarify the roles of p21/Cip1 and p27/Kip1 protein expression, which was involved in G(0)/G(1) arrest and apoptosis induced by TF in human cancer cells, antisense oligodeoxynucleotides (ODNs) specific to p21/Cip1 and p27/Kip1 were used, and the expression of the p21/Cip1 and p27/Kip1 were monitored by immunoblotting analysis. Our data demonstrated that the percentage of the apoptotic cells detected by annexin V/PI analysis in the TF-treated group was clearly attenuated by pretreatment with p27/Kip1-specific ODNs. These results indicated that p27/Kip1 (but not p21/Cip1) protein indeed played a critical role in the TF-induced apoptosis. We also demonstrated that the TF-induced G(0)/G(1) cell-cycle arrest effect was not reversed by TF removal, and this growth inhibition lasted for at least 7 d. Importantly, the occurrence of apoptosis and cell growth arrest was not observed in the TF-treated normal human fibroblast, even at a dose as high as 25 microM. Our study showed the molecular mechanisms for TF-induced cell growth inhibition and the occurrence of apoptosis in human cancer cells.

Ketoconazole potentiates terfenadine-induced apoptosis in human Hep G2 cells through inhibition of cytochrome p450 3A4 activity.

Terfenadine (TF) is a highly potent histamine H1 receptor antagonist that in clinically effective doses is free of significant central nervous system side effects. Ketoconazole (KT) is a worldwide used oral antifungal agent with a broad spectrum of activity against both superficial and systemic mycosis. Simultaneously administration of KT and TF has been reported to induce several potent symptoms including cardiotoxicity, excitotoxicity, inhibition of blood mononuclear cells proliferation, and cardiovascular toxicity. However, the intracellular molecular mechanisms of TF-KT interactions in cells were still uncertain. In this study, we first demonstrated that TF (5-30 microM) induced apoptosis in several types of human cancer cell lines including human hepatoma (Hep G2), colorectal cancer (COLO 205), and fibroblast (CCD 922SK) cells for 24 h. The cellular responses to TF-induced apoptosis were demonstrated to be associated with the p53-signaling pathway, including induction of p53, p21/Cip1, p27/Kip1, bax protein expression and inhibition of bcl-2 protein expression. To realized the role of H1 receptor involved in TF-induced apoptosis, different H1 receptor antagonists including promethazine, mequitazine, and chlorpheniramin (50-100 microM) were administered and demonstrated that these chemicals cannot induced apoptosis through the H1 receptor signaling pathway. Interestingly, we found that the apoptotic effect of TF (2.5 microM) was significantly potentiated by KT (1 microM) treatment in Hep G2 cells through inhibition of the cytochrome p450 3A4 (CYP 3A4) activity. Such results were demonstrated by decreased of the TF activity with recombinant CYP 3A4, which prepared from baculovirus-infected insect cells. Our results provide the molecular basis of TF-KT interaction and this information should allow more rational forecasting of the risk for TF therapy during co-administration of KT.

Cetirizine Decreases Interleukin-4, Interleukin-5, and Interferon-γ Gene Expressions in Nasal-Associated Lymphoid Tissue of Sensitized Mice

Although the action of cetirizine dihydrochloride (cetirizine), a potent histamine H1 receptor antagonist, has been well known, its effect on the cytokine profiles in the nasal immune inductive site has not been elucidated yet. We studied the effect of cetirizine on the cytokine profiles in the nasal-associated lymphoid tissue (NALT), which is a principal mucosal lymphoid tissue of the respiratory tract in rodents. Two different doses of cetirizine were given intraorally for 5 days before the nasal challenge of ovalbumin in sensitized mice. The sensitized group was given normal saline instead of cetirizine, and the nonsensitized group had no sensitization or medication. The cytokine gene expressions in the NALT taken from the mice were investigated with real-time quantitative reverse-transcription polymerase chain reaction. The effect of cetirizine on the allergic symptom score, histamine threshold, and the eosinophil count in the nasal septal mucosa were examined also. Compared with the normal mice, the sensitized mice showed significantly increased levels of interleukin (IL)-4 and IL-5 gene expression although the increase of interferon (INF)-gamma gene expression was not significant. In the cetirizine groups, the levels of expression of IL-4, IL-5, and INF-gamma in the NALT were significantly decreased compared with the sensitized group. The cetirizine groups also showed decreased allergic symptom score, histamine threshold, and eosinophil count in the nasal septal mucosa compared with the sensitized group. In conclusion, cetirizine reduced the levels of expression of IL-4, IL-5, and INF-gamma in the NALT of ovalbumin-sensitized mice. Cetirizine also reduced the acute allergic symptom, histamine sensitivity, and eosinophil count in the nasal septal mucosa.

Benzophenone derivatives and related compounds as potent histamine H3-receptor antagonists and potential PET/SPECT ligands.

Para-substituted aromatic ethers with benzophenone or related structural elements and a 3-(1H-imidazol-4-yl)propyloxy moiety were prepared by Mitsunobu-type ether synthesis or SNAr reaction. Most of the title compounds possess high antagonist potency in histamine H3-receptor assays in vitro as well as in vivo in mouse CNS following oral administration. After defining 4-(3-(1H-imidazol-4-yl)propyloxy)phenyl phenyl methanone as a new lead, structure-activity relationships were investigated for this new class of compounds. Substitution of the meta'-position of the benzophenone moiety with halogen atoms (e.g., iodine, fluorine) led to compounds with high antagonist potency in vitro as well as in vivo (Ki = 9.3 and 4.3 nM, ED50 = 0.7 and 0.47 mg/kg p.o., 18 and 12, respectively). A receptor profile of several functional in vitro assays for several biogenic amine receptors for the meta'-iodinated derivative demonstrated high selectivity toward the histamine H3 receptor.

Effect of Cimetidine on the Pharmacokinetics of Oral Gemifloxacin in Healthy Volunteers

imetidine is a potent histamine H2-receptor antagonist that is used for its ability to inhibit gastric acid secretion. This study investigated the effect of cimetidine on the pharmacokinetics of gemifloxacin, a novel fluoroquinolone antimicrobial agent. This double-blind, randomised, placebo-controlled, two-period crossover study included 12 female and 10 male healthy volunteers who received a single oral dose of gemifloxacin 320mg orally on day 5 of 7 days of administration with either cimetidine 400mg or placebo four times daily. All 22 participants received both drug regimens in a randomised order, with at least a 7-day washout period between regimens. Plasma samples were collected up to 48 hours after drug administration of gemifloxacin and were assayed for gemifloxacin content in order to determine pharmacokinetic parameters. Urine samples were also collected up to 72 hours after drug administration and were assayed for gemifloxacin content. Administration of cimetidine with gemifloxacin increased the area under the plasma concentration-time curve of gemifloxacin from time zero extrapolated to infinity (AUC0-∞) by, on average, 10% [95% confidence interval (CI) —4 to 25%] and increased the maximal plasma concentration (Cmax), by, on average, 6% (95% CI —6 to 20%) relative to results obtained on coadministration of gemifloxacin with placebo. Renal clearance of gemifloxacin was decreased by 28% (95% CI —35 to 19%) when administered with cimetidine, presumably due to inhibition of organic cationic renal transport. This finding is unlikely to be of any clinical relevance. Gemifloxacin was well tolerated by all participants when coadministered with cimetidine or placebo. This study indicated that cimetidine had only minimal effects on the pharmacokinetics of gemifloxacin, which are unlikely to be of any clinical relevance. Gemifloxacin 320mg (as a single dose) was well tolerated by healthy volunteers when coadministered with cimetidine or placebo. The results of this study support the lack of need for dose adjustment of gemifloxacin when coadministered with cimetidine.

Pharmacological and clinical properties of cetirizine hydrochloride

A number of reports have characterized cetirizine as a potent histamine H1-receptor antagonist possessing inhibitory effects on eosinophil chemotaxis. In clinical pharmacological tests, cetirizine markedly reduced wheal and flare responses induced by histamines. The inhibition was fast onset, potent and long-lasting. A single clinical dose of cetirizine was more potent in inhibiting wheal response than other antihistamines such as terfenadine, loratadine, epinastine and ebastine. Cetirizine also inhibited eosinophil chemotaxis in vitro at a concentration easily attained after a clinical dose of 10 mg. Eosinophil infiltration into a site challenged with allergen in vivo was also inhibited. Potent antihistaminic effects of cetirizine afforded fast and strong relief from histamine-induced symptoms such as sneezing and rhinorrhoea in allergic rhinitis and itchy sensation in idiopathic chronic urticaria. Inhibitory effect of cetirizine on eosinophil chemotaxis may alleviate minimal persistent inflammation due to faintly but repeated intake of allergen. Such anti-inflammatory properties of cetirizine may be beneficial in reducing hypersensitivity to normalize the upper respiratory tract and eosinophil-related skin inflammation.