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

Chiral Switch: Between Therapeutical Benefit and Marketing Strategy

Chirality of pharmaceutical substances is an important aspect in drug research because it determines how enantiomers will interact with chiral biological targets. Enantiomers of a chiral drug can have different pharmacokinetic and pharmacological profiles; consequently, using a single pure enantiomer instead of a racemate can enhance the effectiveness and/or safety of the treatment. The tendencies of modern pharmaceutical industry regarding the current market of chiral drugs are divided between the chiral switch of previously used racemates and the development of new enantiopure drugs. The term chiral switch refers to the replacement on the market of a previously approved racemate with its single enantiomer version. The potential advantages of chiral switch can be related to a higher therapeutic index due to better potency, selectivity and fewer adverse effects, faster onset of action and exposure of the patient to lower drug dosages. However, chiral switch is also a strategy that permits manufacturers to keep market exclusivity for chiral pharmaceuticals that have lost their patent protection, even if the pure enantiomers have not demonstrated higher effectiveness or safety profile compared with the racemates.

Levocetirizine and montelukast in the COVID-19 treatment paradigm

Levocetirizine, a third-generation antihistamine, and montelukast, a leukotriene receptor antagonist, exhibit remarkable synergistic anti-inflammatory activity across a spectrum of signaling proteins, cell adhesion molecules, and leukocytes. By targeting cellular protein activity, they are uniquely positioned to treat the symptoms of COVID-19. Clinical data to date with an associated six-month follow-up, suggests the combination therapy may prevent the progression of the disease from mild to moderate to severe, as well as prevent/treat many of the aspects of ‘Long COVID,’ thereby cost effectively reducing both morbidity and mortality. To investigate patient outcomes, 53 consecutive COVID-19 test (+) cases (ages 3–90) from a well-established, single-center practice in Boston, Massachusetts, between March – November 2020, were treated with levocetirizine and montelukast in addition to then existing protocols [2]. The data set was retrospectively reviewed. Thirty-four cases were considered mild (64%), 17 moderate (32%), and 2 (4%) severe. Several patients presented with significant comorbidities (obesity: n = 22, 41%; diabetes: n = 10, 19%; hypertension: n = 24, 45%). Among the cohort there were no exclusions, no intubations, and no deaths. The pilot study in Massachusetts encompassed the first COVID-19 wave which peaked on April 23, 2020 as well as the ascending portion of the second wave in the fall. During this period the average weekly COVID-19 case mortality rate (confirmed deaths/confirmed cases) varied considerably between 1 and 7.5% [37]. FDA has approved a multicenter, randomized, placebo-controlled, Phase 2 clinical trial design, replete with electronic diaries and laboratory metrics to explore scientific questions not addressed herein.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Sensitive Detection of Levocetirizine as a new Generation Antihistamine by Stripping Square Wave Voltammetry

Background::

new and selective electrochemical sensor was developed for the determination of levocetirizine dihydrochloride, which is an antihistaminic drug.

Method::

The investigation was performed by using cyclic, differential pulse and square wave voltammetric methods on the β-cyclodextrin modified glassy carbon electrode. It is thereby planned to obtain information about levocetirizine determination and its mechanism.

Result::

The efficiency of experimental parameters including pH, scan rate, and accumulation potential and time on the anodic response of levocetirizine dihydrochloride was studied. By employing the developed method and under optimized conditions, the current showed linear dependence with a concentration in the range between 2 × 10-8 M and 6 × 10-6 M in pH 2.0 Britton Robinson (BR) buffer.

Conclusion::

The achieved limits of detection and quantification were found as 3.73 × 10-10 M and 1.24 × 10-9 M, respectively. In addition, the possibility of applying the developed sensor for real sample analysis was investigated, so β-cyclodextrin modified glassy carbon electrode was used to determine levocetirizine dihydrochloride in Xyzal® tablet dosage form. Finally, this sensor was successfully applied to the real sample as a selective, simple, reproducible, repeatable electrochemical sensor.

Racemisation in Chemistry and Biology

The two enantiomers of a compound often have profoundly different biological properties and thus their liability to racemisation in aqueous solutions is an important piece of information. The authors reviewed the available data concerning the process of racemisation in vivo, in the presence of biological molecules (e.g., racemase enzymes, serum albumin, cofactors and derivatives) and under purely chemical but aqueous conditions (acid, base and other aqueous systems). Mechanistic studies are described critically in light of reported kinetic data. The types of experimental measurement that can be used to effectively determine rate constants of racemisation in various conditions are discussed and the data they provide is summarised. The proposed origins of enzymatic racemisation are presented and suggest ways to promote the process that are different from processes taking place in bulk water. Experimental and computational studies that provide understanding and quantitative predictions of racemisation risk are also presented.

Focus on the cetirizine use in clinical practice: a reappraisal 30 years later

Antihistamines are currently one of the most commonly administered categories of drugs. They are used to treat symptoms that are secondary to histamine release, which is typical of certain allergic conditions, including rhinitis, conjunctivitis, asthma, urticaria, and anaphylaxis. Cetirizine belongs to the second-generation family, so, it is very selective for peripheral H1 receptors, is potent and quickly relieves symptoms, exerts additional anti-allergic/anti-inflammatory effects, and is usually well-tolerated. It has been marketed 30 years ago. In these years, a remarkable body of evidence has been built. The current review provides a practical update on the use of cetirizine in clinical practice.

Structural and clinical impact of anti-allergy agents: An overview

Allergic disorders are markedly rising in industrialized countries. The identification of compounds that trigger the immunoglobulin E (IgE)-dependent allergic reaction remain the means to improve the quality of life by limiting patient's exposure to critical allergens. Information concerning the treatment and onset of allergic disorders including atopic dermatitis, allergic rhinitis, and bronchial asthma has been provided by the research over the past decade. Recent studies also indicated that allergic inflammation is associated closely with their exacerbation and progression and indeed is the basic pathophysiology of allergic diseases. As a result of immunological and molecular biological studies our understanding of the mechanism of allergic inflammation with regard to therapeutic agents has improved. While much effort has been paid to developing a new anti-allergic agent, the allergic disease has yet to be completely conquered. The more extensive research will allow the development of new therapeutics to combat allergic diseases. Currently, with respect to mechanism of action anti-allergy drugs are classified into five types including histamine H₁ antagonists, leukotriene antagonists, Th₂ cytokine inhibitors, thromboxane A₂ inhibitors and mediator-release inhibitors. The use of two or more anti-allergy agents together is not acknowledged at present, but this will be the subject of research in the future because with different mechanisms of action anti-allergy agents used at the same time will theoretically increase their effects. This review article focuses on anti-allergy agents highlighting their applications, clinical trials and recent advancement on drugs.

Stereoisomeric profiling of chiral pharmaceutically active compounds in wastewaters and the receiving environment - A catchment-scale and a laboratory study

Chiral pharmaceutically active compounds (cPACs) are not currently governed by environmental regulation yet are expected to be in the future. As cPACs can exert stereospecific toxicity in the aquatic environment, it is essential to better understand their stereoselective behaviour here. Therefore, this study aims to provide a new perspective towards comprehensive evaluation of cPACs at a river catchment level, including their stereochemistry as a chemical phenomenon driving fate of chiral molecules in the environment. A large spatial and temporal monitoring program was performed in Southwest England. It included 5 sewage treatment works and the receiving waters of the largest river catchment in Southwest England. Simultaneously, lab-scale microcosm studies in simulated activated sludge bioreactors and river water microcosm were performed to evaluate stereoselective degradation of cPACs. A multi-residue enantioselective method allowed the analysis of a total of 18 pairs of enantiomers and 3 single enantiomers in wastewater and river water samples. Our monitoring program revealed: (1) spatial and temporal variations of cPACs in influent wastewaters resulting from different patterns of usage as well as an (2) enantiomeric enrichment of cPACs, likely due to human metabolism, despite their commercialization as racemic mixtures. A similar chiral signature was observed in effluent and receiving waters. Stereoselective degradation was observed in trickling filters (TF) for naproxen, ketoprofen, cetirizine and 10,11-dihydroxy-10-hydroxycarbamazepine, in sequencing batch reactors (SBR) for ifosfamide and in activated sludge (AS) for cetirizine. The extent of enantiomer-specific fate was wastewater treatment dependent in the case of naproxen (TF showed higher stereoselectivity than AS and SBR) and cetirizine (TF and AS showed higher stereoselectivity than SBR) due to differing microbial population. Furthermore, stereoselective degradation of naproxen was highly variable among STWs using similar treatments (TF) and operating in the same region. Microbial stereoselective degradation was also confirmed by both activated and river water simulated microcosm for chloramphenicol, ketoprofen, indoprofen, naproxen and 10,11-dihydroxy-10-hydroxycarbamazepine. Results from our large scale river catchment monitoring study and lab simulated microcosm show wide-ranging implications of enantiomerism of cPACs on environmental risk assessment (ERA). As two enantiomers of the same compound show different biological effects (e.g. toxicity), their non-racemic presence in the environment might lead to inaccurate ERA. This is because current ERA approaches do not require analysis at enantiomeric level.

The problem of racemization in drug discovery and tools to predict it

INTRODUCTION

Racemization has long been an ignored risk in drug development, probably because of a lack of convenient access to good tools for its detection and an absence of methods to predict racemization risk. As a result, the potential effects of racemization have been systematically underestimated. Areas covered: Herein, the potential effects of racemization are discussed through a review of drugs for which activity and side effects for both enantiomers are known. Subsequently, drugs known to racemize are discussed and the authors review methods to predict racemization risk. Application of a method quantitatively predicting racemization risk to databases of compounds from the medicinal chemistry literature shows that success in clinical trials is negatively correlated with racemization risk. Expert opinion: It is envisioned that a quantitative method of predicting racemization risk will remove a blind spot from the drug development pipeline. Removal of the blind spot will make drug development more efficient and result in less late-stage attrition of the drug pipeline.

Differential Regulation of Thermodynamic Binding Forces of Levocetirizine and (S)-Cetirizine by Lys191 in Human Histamine H₁ Receptors

Cetirizine is a zwitterionic second-generation antihistamine containing R- and S-enantiomers, levocetirizine, and (S)-cetirizine. Levocetirizine is known to have a higher affinity for the histamine H₁ receptors than (S)-cetirizine; ligand-receptor docking simulations have suggested the importance of the formation of a salt bridge (electrostatic interaction) between the carboxylic group of levocetirizine and the Lys191 residue at the fifth transmembrane domain of human histamine H₁ receptors. In this study, we evaluated the roles of Lys191 in the regulation of the thermodynamic binding forces of levocetirizine in comparison with (S)-cetirizine. The binding enthalpy and entropy of these compounds were estimated from the van 't Hoff equation, by using the dissociation constants obtained from their displacement curves against the binding of [³H]mepyramine to the membrane preparations of Chinese hamster ovary cells expressing wild-type human H₁ receptors and their Lys191 mutants to alanine at various temperatures. We found that the higher binding affinity of wild-type H₁ receptors for levocetirizine than (S)-cetirizine was achieved by stronger forces of entropy-dependent hydrophobic binding of levocetirizine. The mutation of Lys191 to alanine reduced the affinities for levocetirizine and (S)-cetirizine, through a reduction in the entropy-dependent hydrophobic binding forces of levocetirizine and the enthalpy-dependent electrostatic binding forces of (S)-cetirizine. These results suggested that Lys191 differentially regulates the binding enthalpy and entropy of these enantiomers, and that Lys191 negatively regulates the enthalpy-dependent electrostatic binding forces of levocetirizine, contrary to the predictions derived from the ligand-receptor docking simulations.

In vitro drug interaction of levocetirizine and diclofenac: Theoretical and spectroscopic studies

Levocetirizine dihydrochloride is known to interact with some anti-inflammatory drugs. We report here a comprehensive integrated theoretical and experimental study for the in vitro drug interaction between levocetirizine dihydrochloride (LEV) and diclofenac sodium (DIC). The interaction of the two drugs was confirmed by the molecular ion peak obtained from the mass spectrum of the product. Moreover, FTIR and ¹HNMR spectra of the individual drugs and their interaction product were inspected to allocate the possible sites of interaction. In addition, quantum mechanical DFT calculations were performed to search for the interaction sites and to verify the types of interactions deduced from the spectroscopic studies such as charge-transfer and non-bonding π-π interactions. It was found that the studied drugs interact with each other in aqueous solution via four types of interactions, namely, ion-pair formation, three weak hydrogen bonds, non-bonding π-π interactions and charge-transfer from DIC to LEV.

A Novel Two-Step Liquid-Liquid Extraction Procedure Combined with Stationary Phase Immobilized Human Serum Albumin for the Chiral Separation of Cetirizine Enantiomers along with M and P Parabens

The research into the separation of drug enantiomers is closely related to the safety and efficiency of the drugs. The aim of this study was to develop a simple and validated HPLC method to analyze cetirizine enantiomers. In the case of liquid dosage forms, besides the active substance in large amounts there are usually also inactive ingredients such as methyl- and propylparaben. Unfortunately, these compounds can interfere with the analyte, inter alia during chiral separation of the analyte enantiomers. The proposed innovative two-step liquid-liquid extraction procedure allowed for the determination of cetirizine enantiomers (along with M and P parabens) also in liquid dosage forms. The main focus of this study was the chromatographic activity of cetirizine dihydrochloride on the proteinate-based chiral stationary phase. The chromatographic separation of cetirizine enantiomers was performed on an immobilized human serum albumin (HSA) column for the first time. Measurements were performed at a wavelength of 227 nm. Under optimal conditions, baseline separation of two enantiomers was obtained with 1.43 enantioseparation factor (α) and 1.82 resolution (R_s). Finally, the proposed method was successfully applied to the selected pharmaceutical formulations.

Crystal structure of equine serum albumin in complex with cetirizine reveals a novel drug binding site

Serum albumin (SA) is the main transporter of drugs in mammalian blood plasma. Here, we report the first crystal structure of equine serum albumin (ESA) in complex with antihistamine drug cetirizine at a resolution of 2.1Å. Cetirizine is bound in two sites--a novel drug binding site (CBS1) and the fatty acid binding site 6 (CBS2). Both sites differ from those that have been proposed in multiple reports based on equilibrium dialysis and fluorescence studies for mammalian albumins as cetirizine binding sites. We show that the residues forming the binding pockets in ESA are highly conserved in human serum albumin (HSA), and suggest that binding of cetirizine to HSA will be similar. In support of that hypothesis, we show that the dissociation constants for cetirizine binding to CBS2 in ESA and HSA are identical using tryptophan fluorescence quenching. Presence of lysine and arginine residues that have been previously reported to undergo nonenzymatic glycosylation in CBS1 and CBS2 suggests that cetirizine transport in patients with diabetes could be altered. A review of all available SA structures from the PDB shows that in addition to the novel drug binding site we present here (CBS1), there are two pockets on SA capable of binding drugs that do not overlap with fatty acid binding sites and have not been discussed in published reviews.

Chiral Switch Drugs for Asthma and Allergies: True Benefit or Marketing Hype

Enantiomers are one of several possible molecular configurations present in a drug that has at least 1 chiral center. A drug containing 2 or more enatiomers is called a racemic mixture. Enatiomers are being developed from racemic mixtures as drugs in their own right often to extend patent protection of highly popular drugs. However, the therapeutic advantages of single enantiomer drugs developed for respiratory use such as levalbuterol, arformoterol, and levocetirizine over their racemate has been disappointing. In addition, single enantiomer drugs may be several fold more expensive than the racemic drug. New single enantiomer drugs, which are stable (no interconversion back to the racemate) and have fewer adverse effects and a more predictable pharmacodynamic or pharmacokinetic profile would confer a therapeutic advantage and thus would be beneficial for clinical use.

The clinical use of cetirizine in the treatment of allergic rhinitis

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Formulation and evaluation of fast dissolving films of levocitirizine di hydrochloride

Introduction:

Levocetirizine dihydrochloride is an orally active, third-generation non-sedative antihistamine used in the symptomatic relief of seasonal and perennial allergic rhinitis. The present work aimed at preparing quick release films of levocetirizine with the purpose of developing a dosage form for a very quick onset of action, which is beneficial in managing severe conditions of allergies, aiding in the enhancement of bioavailability, and is very convenient for administration, without the problem of swallowing and using water.

Materials and Methods:

The films of levocetirizine dihydrochloride were prepared by using polymers such as hydroxypropyl methylcellulose (HPMC) and polyvinyl alcohol (PVA), as either single polymer or in combination of two, by a solvent casting method. They were evaluated for physical characteristics such as uniformity of weight, thickness, folding endurance, drug content uniformity, surface pH, percentage elongation, and tensile strength, and gave satisfactory results. The formulations were subjected to disintegration, in vitro drug release tests, and in vivo studies on rats.

Results:

A marked increase in the dissolution rate was exhibited by fast-dissolving films of levocetirizine dihydrochloride containing HPMC as a polymer, when compared to conventional tablets. The haloperidol-induced catalepsy, milk-induced leukocytosis, and nasal provocation in vivo studies in rats proved that the fast-dissolving films of levocetirizine dihydrochloride produced a faster onset of action compared to the conventional tablets.

Conclusions:

Fast dissolving films of levocetirizine dihydrochloride can be considered suitable for clinical use in the treatment of allergic rhinitis and other conditions of allergies, where a quicker onset of action for a dosage form is desirable along with the convenience of administration.

Chitosan-based thermosensitive hydrogel as a promising ocular drug delivery system: Preparation, characterization, and in vivo evaluation

The purpose of this study was to evaluate the feasibility of in situ thermosensitive hydrogel based on chitosan in combination with disodium α-d-Glucose 1-phosphate (DGP) for ocular drug delivery system. Aqueous solution of chitosan/DGP underwent sol–gel transition as temperature increased which was flowing sol at room temperature and then turned into non-flowing hydrogel at physiological temperature. The properties of gels were characterized regarding gelation time, gelation temperature, and morphology. The sol-to-gel phase transition behaviors were affected by the concentrations of chitosan, DGP and the model drug levocetirizine dihydrochloride (LD). The developed hydrogel presented a characteristic of a rapid release at the initial period followed by a sustained release and remarkably enhanced the cornea penetration of LD. The results of ocular irritation demonstrated the excellent ocular tolerance of the hydrogel. The ocular residence time for the hydrogel was significantly prolonged compared with eye drops. The drug-loaded hydrogel produced more effective anti-allergic conjunctivitis effects compared with LD aqueous solution. These results showed that the chitosan/DGP thermosensitive hydrogel could be used as an ideal ocular drug delivery system in terms of the suitable sol–gel transition temperature, mild pH environment in the hydrogel as well as the organic solvent free.

Stereoselective and multiple carrier-mediated transport of cetirizine across Caco-2 cell monolayers with potential drug interaction

The aim of this study was to explore potential transport mechanisms of cetirizine enantiomers across Caco-2 cells. Cetirizine displayed polarized transport at concentrations ranging from 4.0 to 80.0 microM, with the permeability in the secretory direction being 1.4- to 4.0-fold higher than that in the absorptive direction. Cetirizine enantiomers were transported distinctively different from each other. In the presence of inhibitors of P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP), the absorptive transport was enhanced and secretory efflux was diminished. When verapamil, indomethacin, or probenecid were present, the difference in the absorptive permeability of R-cetirizine and S-cetirizine substantially intensified, whereas quinidine could eliminate. R-cetirizine significantly increased the efflux ratio of rhodamine-123 and doxorubicin in a fashion indicative of the upregulation of P-gp and MRP activities. However, S-cetirizine played a role of an inhibitor for P-gp and MRP. Ranitidine modified the absorption of cetirizine enantiomers, suggesting that the potential drug-drug interaction would significantly change the cetirizine pharmacokinetics. In conclusion, the results indicated that there are several efflux transporters including P-gp and MRP participating the absorption and efflux of cetirizine, which showed enantioselectivity in the transmembrane process. In addition, both P-gp and MRP functions could be modulated by cetirizine in chiral discriminative ways.

Drug metabolism and pharmacokinetics

In this article, aspects of absorption, distribution, metabolism, and excretion have been described bearing in mind the pathogenesis of allergic diseases and their possible therapeutic opportunities. The importance of the routes of administration of the different therapeutic groups has been emphasized. The classical aspects of drug metabolism and disposition related to oral administration have been reviewed, but special emphasis has been given to intranasal, cutaneous, transdermal, and ocular administration as well as to the absorption and the subsequent bioavailability of drugs. Drug-metabolizing enzymes and transporters present in extrahepatic tissues, such as nasal mucosa and the respiratory tract, have been particularly discussed. As marketed antiallergic drugs include both racemates and enantiomers, aspects of stereoselective absorption, distribution, metabolism, and excretion have been discussed. Finally, a new and promising methodology, microdosing, has been presented, although it has not yet been applied to drugs used in the treatment of allergic diseases.

Study on the interaction of levocetirizine dihydrochloride with human serum albumin by molecular spectroscopy

The interaction between cetirizine dihydrochloride and human serum albumin (HSA) has been examined by the spectroscopic techniques first. According to Stern-Volmer equation at different temperatures and the UV-vis spectra examination it was demonstrated that HSA fluorescence quenching initiated by levocetirizine was static. The values of binding constant (K(A)) and the number of binding sites (n) for levocetirizine and HSA were smaller than those for cetirizine and HSA, which meant that the transport of drug was regulated by the stereoselectivity of HSA to the enantiomer. The effect of the non-enzymatic glycosylation (NEG) on the interaction between levocetirizine and HSA signified that the administration of levocetirizine for diabetes should be different from the normal. The positive DeltaS(o) and negative DeltaH(o) indicated that ionic interaction played a major role between levocetirizine and HSA. Circular dichroism (CD) measurement showed that the secondary structure of HSA has changed in the presence of levocetirizine, and alpha-helical content decreased from 63.1% for free HSA to 54.9% for combined HSA, and accordingly the other secondary structure (beta-strand, beta-turns and others) contents increased to some extent. Finally, by the competitive binding experiments it was deduced that levocetirizine specifically bound to HSA in the region of site II, which meant the curative effect of levocetirizine should be reconsidered when it was administrated together with other site II drugs.

The comparison of cetirizine, levocetirizine and placebo for the treatment of childhood perennial allergic rhinitis

Cetirizine (Zyrtec) is a potent and long-acting second-generation histamine H1- receptor antagonist for the treatment of allergic disease, such as allergic rhinitis and chronic idiopathic urticaria, in adult and child. It is a racemic mixture of levocetirizine (Xyzal) and dextrocetirizine. The purpose of this present study was to compare the efficacy of cetirizine, levocetirizine and placebo for the treatment of pediatric perennial allergic rhinitis. 74 perennial allergic rhinitis patients, aged 6 to 12 years old, assigned to 1 of 3 treatment groups for 12 weeks randomly. The effects of the three agents were compared with the Pediatric Rhinoconjunctivitis Quality of Life Questionnaire (PRQLQ) and Total Symptom Score (TSS) by diary. Nasal peak expiratory flow rate (nPEFR) and laboratory examinations including serum immunoglobulin E level, eosinophil cationic protein (ECP), blood eosinophil counts and eosinophil percentage in a nasal smear were evaluated among the three groups. The results revealed that both cetirizine and levocetirizine improved TSS in comparison with the placebo group, and ceterizine appeared to be more efficacious than levocetirizine at week 8 and week 12. The PRQLQ score showed significant decreased both in cetirizine and levocetirizine group, but there was no statistic significant difference between both groups. The eosinophil proportion in a nasal smear significantly decreased among the cetirizine in comparison with the placebo group but there was no statistic significant in levocetirizine groups. Both cetirizine and levocetirizine showed significant improvement in nPEFR in comparison with the placebo group, and ceterizine appeared to be more efficacious than levocetirizine. The 12-week treatment program showed that cetirizine was more effectious than levocetirizine.

Stereoconfiguration of antiallergic and immunologic drugs

OBJECTIVE

To review the concept of chirality and its current role in the pharmacology of antiallergic, antiasthmatic, and immunologic agents.

DATA SOURCES

Ovid MEDLINE and PubMed databases from 1950 to the present time were searched.

STUDY SELECTION

Articles that described the pharmacology of chiral antiallergic, antiasthmatic, and immunologic medications were used for this review.

RESULTS

Stereoselectivity affects the pharmacologic profiles of medications in different ways from class to class and within the classes. This summary illustrates that enantiomers differ not only in potency in receptor binding and physiologic effects but also in pharmacokinetic parameters such as volume of distribution, plasma protein binding, metabolism, and clearance. Different enantiomers may produce unrelated pharmacologic effects as well. This review summarizes the variety of possible effects that different stereoisomers may produce and further underlines the importance of the purification and in-depth analysis of chiral compounds.

CONCLUSION

Chirality plays an important role in pharmacokinetics and pharmacodynamics of various pharmaceutical agents. The importance of stereoisomeric purity in the pharmacologic industry has increased during the past decade as demonstrated by the increased number of studies that examined the in vivo and in vitro effects produced by changes in stereoconfiguration of pharmaceutical agents. This review highlights such effects in certain frequently used medications used in the treatment of asthma and various allergic and immunologic disorders.

Comparison of HPLC and CE methods for the determination of cetirizine dihydrochloride in human plasma samples

Two methods, capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC), for analysis of cetirizine dihydrochloride in small sample volumes of human plasma were compared. The CE and HPLC assays were developed and validated by analyzing a series of plasma samples containing cetirizine dihydrochloride in different concentrations using these two methods. The extraction procedure is simple and no complicated purification steps or derivatization are required. The analysis time in the HPLC method was shorter than that in the CE method, but solvent consumption was considerably lower in the CE method. The calibration curve was linear to at least 10-1000 ng/mL both for CE and HPLC with r(2) = 0.9993 and r(2) = 0.9994, respectively. The detection limits for cetirizine dihydrochloride were 3 and 5 ng/mL with CE and HPLC (a UV detector was applied in the both cases), respectively. Both methods were selective, robust and specific, allowing reliable quantification of cetirizine dihydrochloride, and could be useful for clinical and biomedical investigations.

Levocetirizine: a review of its use in the management of allergic rhinitis and skin allergies

Levocetirizine (Xyzal) is a selective, potent, oral histamine H(1) receptor antagonist of the latest generation that is licensed for the symptomatic treatment of allergic rhinitis (including persistent allergic rhinitis [PER]) and chronic idiopathic urticaria (CIU). Large, well designed trials indicate that levocetirizine is effective and generally well tolerated in the treatment of allergic rhinitis and CIU. Its pharmacological profile offers many positive aspects: a rapid onset and long duration of antihistaminic effect; rapid absorption and high bioavailability; a low potential for drug interactions; a low volume of distribution; and a lack of effect on cognition, psychomotor function and the cardiovascular system. Allergen challenge chamber studies suggest that levocetirizine has better efficacy than desloratadine, loratadine or fexofenadine. Well controlled, long-term studies with other later-generation H(1) receptor antagonists are required to fully define its clinical profile relative to other agents in this class. Overall, levocetirizine is a valuable addition to the oral H(1) receptor antagonists available for the treatment of allergic rhinitis and as first-line therapy in patients with CIU.

Chiral separation of cetirizine by capillary electrophoresis

Chiral separation of cetirizine, a second-generation H(1)-antagonist, was studied by CD-mediated CE. Several parameters, including pH, CD type, buffer concentration, type of co-ion, applied voltage and temperature, were investigated. The best conditions for chiral separation were obtained using a 75 mM triethanolamine-phosphate buffer (pH 2.5) containing 0.4 mg/mL heptakis(2,3-diacetyl-6-sulfato)-beta-CD and 10% ACN. Online UV detection was performed at 214 nm, a voltage of 20 kV was applied and the capillary was temperature controlled at 25 degrees C by liquid cooling. Hydrodynamic injection was performed for 1 s. The method was validated for the quantification of levocetirizine in tablets and for enantiomeric purity testing of the drug substance. Selectivity, linearity, LOD and LOQ, precision and accuracy were evaluated for both methods. The amount of levocetirizine dihydrochloride in the commercially available tablets was quantified and was found to be within the specification limits of the claimed amount (5 mg). The amount of distomer in levocetirizine drug substance was found to be 0.87 +/- 0.09% w/w, which is in agreement with the certificate of analysis supplied by the company.

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.

A Review of the Evidence from Comparative Studies of Levocetirizine and Desloratadine for the Symptoms of Allergic Rhinitis

BACKGROUND

Levocetirizine and desloratadine are newer antihistamines indicated for the treatment of allergic rhinitis and chronic idiopathic urticaria.

OBJECTIVE

This article discusses the pharmacokinetics and pharmacodynamics of levocetirizine and desloratadine and reviews studies that have directly compared the effects of these 2 drugs in allergic rhinitis and urticaria.

METHODS

Relevant articles were identified through a search of MEDLINE from 1999 through 2004 using the main search terms levocetirizine and desloratadine.

RESULTS

Levocetirizine is absorbed rapidly and reaches a steady-state plasma concentration more quickly than does desloratadine. It is also metabolized to a lesser extent than desloratadine, has a lower V(d), and has higher specificity for histamine(1) receptors. Eight well-controlled trials were identified that directly compared the effects of levocetirizine and desloratadine in the skin and nose of healthy individuals and patients with allergic rhinitis. Drug activity was measured in terms of wheal, flare, and itch reactions; nasal symptoms or symptom scores; increases in concentrations of inflammatory markers; or facial thermography. In most of these trials, levocetirizine had a faster onset and greater consistency of effect than desloratadine. The differences in the pharmacokinetic and pharmacodynamic profiles of the 2 drugs may partially explain these clinical findings.

CONCLUSIONS

Levocetirizine may be preferred to desloratadine as a treatment option for allergic rhinitis because of its faster onset of action and greater consistency of effect. Although comparative studies in chronic idiopathic urticaria are not available, data from histamine-induced wheal and flare studies in healthy volunteers suggest that levocetirizine may be more effective in preventing itching than desloratadine.

Roles of histamine and its receptors in allergic and inflammatory bowel diseases

Mast cell has a long history of being recognized as an important mediator-secreting cell in allergic diseases, and has been discovered to be involved in IBD in last two decades. Histamine is a major mediator in allergic diseases, and has multiple effects that are mediated by specific surface receptors on target cells. Four types of histamine receptors have now been recognized pharmacologically and the first three are located in the gut. The ability of histamine receptor antagonists to inhibit mast cell degranulation suggests that they might be developed as a group of mast cell stabilizers. Recently, a series of experiments with dispersed colon mast cells suggested that there should be at least two pathways in man for mast cells to amplify their own activation-degranulation signals in an autocrine or paracrine manner. In a word, histamine is an important mediator in allergic diseases and IBD, its antagonists may be developed as a group of mast cell stabilizers to treat these diseases.

Levocetirizine: the allergist’s arsenal grows larger

Antihistamines are the cornerstone of treatment for many allergic diseases, such as allergic rhinitis and chronic urticaria. Since the discovery of their beneficial effects in the 1940s, scientists have found molecules with greater selectivity to block specific histamine receptors without some of the detrimental side effects that are seen if antihistamines cross the blood-brain barrier. Levocetirizine is the active enantiomer of cetirizine and a selective H(1)-histamine blocker. It exhibits many favourable characteristics of an ideal antihistamine, both pharmacodynamically and pharmacokinetically, including high bioavailability, rapid onset of action, limited distribution and low degree of metabolism. Furthermore, clinical trials indicate that it is safe and effective for the treatment of allergic rhinitis and chronic urticaria with a minimal amount of untoward effects.

Comparison of pharmacokinetics and metabolism of desloratadine, fexofenadine, levocetirizine and mizolastine in humans

Abstract Absorption, distribution, metabolism and excretion of desloratadine, fexofenadine, levocetirizine, and mizolastine in humans have been compared. The time required to reach peak plasma levels (tmax) is shortest for levocetirizine (0.9 h) and longest for desloratadine (> or =3 h). Steady-state plasma levels are attained after about 6 days for desloratadine, 3 days for fexofenadine, 2-3 days for mizolastine and by the second day for levocetirizine. The apparent volume of distribution is limited for levocetirizine (0.4 L/kg) and mizolastine (1-1.2 L/kg), larger for fexofenadine (5.4-5.8 L/kg) and particularly large for desloratadine (approximately 49 l/kg). Fexofenadine and levocetirizine appear to be very poorly metabolized (approximately 5 and 14% of the total oral dose, respectively). Desloratadine and mizolastine are extensively metabolized. After administration of 14C-levocetirizine to healthy volunteers, 85 and 13% of the radioactivity are recovered in urine and faeces, respectively. In contrast, faeces are the preferential route of excretion for 14C-fexofenadine (80% vs. 11% of the radioactive dose in urine). The corresponding values are 41% (urine) and 47% (faeces) for 14C-desloratadine, 84-95% (faeces) and 8-15% (urine) for 14C-mizolastine. The absolute bioavailability is 50-65% for mizolastine; it is high for levocetirizine as the percentage of the drug eliminated unchanged in the 48 h urine is 77% of the oral dose; the estimation for fexofenadine is at least 33%; no estimation was found for desloratadine. Fexofenadine is a P-glycoprotein (P-gp) substrate and P-gp is certainly involved both in the poor brain penetration by the compound and, at least partially, in a number of observed drug interactions. An interaction of desloratadine with P-gp has been suggested in mice, whereas the information on mizolastine is very poor. The fact that levocetirizine is a substrate of P-gp, although weak in an in vitro model, could contribute to prevent drug penetration into the brain, whereas it is unlikely to be of any clinical relevance for P-gp-mediated drug interactions.