Efficacy and safety of Montelukast-Levocetirizine Combination Therapy in Combined Allergic Rhinitis and Asthma Syndrome: A Systematic Review and Meta-Analysis.

OBJECTIVE: This meta-analysis aims to evaluate the efficacy and safety of montelukast combined with levocetirizine in the treatment of allergic rhinitis with asthma, and to provide objective and effective evidence-based medical evidence for clinical use. DATA SOURCES: Pubmed, Web of Science, Cochrane Library, WANFANG DATA, CNKI, and Chinese BioMedical Literature Database were retrieved to identify records related to Montelukast combined with levocetirizine in the treatment of allergic rhinitis with asthma. STUDY SELECTIONS: First, the eligibility criteria were employed to screen search results. Then, two investigators independently assessed titles, abstracts, and the full text of all retrieved references to identify potentially eligible studies. RESULTS: As of 2024-02-03, a total of 6 articles were included in this meta-analysis, covering 2950 patients with allergic rhinitis with asthma. The meta-analysis results exhibited a pooled NSS of -1.28 (95%CI: -1.64 to -0.92), suggesting that the combination of montelukast and levocetirizine was effective in the treatment of nasal symptoms of allergic rhinitis complicated with asthma. The meta-analysis of controlled trials showed that the SMD of NSS in the group of Montelukast combined with levocetirizine was -2.56 (95%CI: -2.77 to -2.35). The result indicated that compared with the control group, the combination of montelukast with levocetirizine significantly improved the symptoms of allergic rhinitis. CONCLUSION: In summary, this meta-analysis demonstrated the efficacy of montelukast combined with levocetirizine in the treatment of nasal symptoms in AR with asthma, indicating that the combination of montelukast with levocetirizine is more effective in improving symptoms of allergic rhinitis than monotherapy and has good safety.

Montelukast treatment response according to eosinophil-derived neurotoxin level in children with allergic rhinitis.

BACKGROUND: Eosinophil-derived neurotoxin (EDN) is an important biomarker of eosinophilic inflammation. METHODS: This study evaluated Montelukast treatment response according to EDN concentration in children with perennial allergic rhinitis (PAR). Fifty-two children with PAR were recruited and took a combination of Montelukast (5mg) and Levocetirizine (5mg) "Mont/Levo Group" or only Montelukast (5mg) "Mont Group" for 4 weeks. All caregivers were instructed to record rhinitis symptoms for 4 weeks. EDN was measured before and after treatment. RESULTS: Daytime nasal symptom scores (DNSS) significantly decreased in both the Mont/Levo (p = 0.0001; n = 20) and Mont Group (p < 0.0001; n = 20), but there were no significant differences between the two groups. EDN concentration also significantly decreased after treatment in both groups (p < 0.0001 and p < 0.001, respectively). For secondary analysis, children with a high initial EDN concentration (EDN ≥ 53 ng/mL) were placed in the "High EDN Group", while those with a lower initial EDN concentration (EDN < 53 ng/mL) were put in the "Low EDN Group". Both groups experienced significant reductions in DNSS after either treatment regimen (p < 0.0001 and p = 0.0027, respectively) but the High EDN Group had greater reductions. EDN concentrations in the High EDN Group decreased significantly from either treatment (p < 0.0001). CONCLUSION: We found that children with AR and a high serum EDN concentration may respond well to Montelukast treatment. A therapeutic strategy using EDN concentrations in patients with AR to evaluate therapeutic response may help improve quality of care.

Efficacy of levocetirizine in isolated rat tracheal smooth muscle.

Histamine receptor-1 (H1) antagonists like levocetirizine are frequently used nowadays to treat rhinitis patients who experience rhinorrhea and sneezing. The trachea may be affected by the H1 antagonist when it is used to treat nasal symptoms, either orally or through inhalation. The purpose of this study was to ascertain in vitro effects of levocetirizine on isolated tracheal smooth muscle. As a parasympathetic mimetic, methacholine (10-6 M) causes contractions in tracheal smooth muscle, which is how we tested effectiveness of levocetirizine on isolated rat tracheal smooth muscle. We also tested the drug's impact on electrically induced tracheal smooth muscle contractions. The impact of menthol (either before or after) on the contraction brought on by 10-6 M methacholine was also investigated. According to the results, the addition of levocetirizine at concentrations of 10-5 M or more caused a slight relaxation in response to methacholine's 10-6 M contraction. Levocetirizine could prevent spike contraction brought on by electrical field stimulation (EFS). As the concentration rose, it alone had a neglect effect on the trachea's basal tension. Before menthol was applied, levocetirizine might have also inhibited the function of the cold receptor. According to this study, levocetirizine might potentially impede the parasympathetic function of the trachea. If levocetirizine was used prior to menthol addition, it also reduced the function of cold receptors.

Levocetirizine-Loaded Electrospun Fibers from Water-Soluble Polymers: Encapsulation and Drug Release.

Electrospun fibers containing levocetirizine, a BCS III drug, were prepared from three water-soluble polymers, hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA). Fiber-spinning technology was optimized for each polymer separately. The polymers contained 10 wt% of the active component. An amorphous drug was homogeneously distributed within the fibers. The solubility of the drug in the polymers used was limited, with a maximum of 2.0 wt%, but it was very large in most of the solvents used for fiber spinning and in the dissolution media. The thickness of the fibers was uniform and the presence of the drug basically did not influence it at all. The fiber diameters were in the same range, although somewhat thinner fibers could be prepared from PVA than from the other two polymers. The results showed that the drug was amorphous in the fibers. Most of the drug was located within the fibers, probably as a separate phase; the encapsulation efficiency proved to be 80-90%. The kinetics of the drug release were evaluated quantitatively by the Noyes-Whitney model. The released drug was approximately the same for all the polymers under all conditions (pH), and it changed somewhere between 80 and 100%. The release rate depended both on the type of polymer and pH and varied between 0.1 and 0.9 min-1. Consequently, the selection of the carrier polymer allowed for the adjustment of the release rate according to the requirements, thus justifying the use of electrospun fibers as carrier materials for levocetirizine.

Enantioselective Intramolecular α-Arylation of Benzylamine Derivatives: Synthesis of a Precursor to Levocetirizine.

A practical, transition metal-free method allows the enantioselective synthesis of α,α-diarylmethylamines by asymmetric α-arylation of benzylamines. Enantioselective lithiation of N'-aryl-N-benzyl-N-isopropyl ureas using a chiral lithium amide base generates a benzyllithium that undergoes an unactivated stereospecific intramolecular nucleophilic aromatic substitution to generate an α,α-diarylmethylamine in the form of its urea derivative, in up to >99 % ee. Treatment with acid induces an "azatropic shift" with retention of configuration, the product of which may be hydrolysed to the target amine.

The Elusive Structure of Levocetirizine Dihydrochloride Determined by Electron Diffraction.

Levocetirizine is an orally administrated, second-generation antihistaminic active pharmaceutical ingredient that has been used to treat symptoms of allergy and long-term hives for over 25 years. Despite the wide use of this compound, its crystal structure has remained unknown. Here we report the application of 3D electron diffraction (3D ED)/Micro-crystal electron diffraction (MicroED) to determine the crystal structure of Levocetirizine dihydrochloride directly from crystalline powders that were extracted from commercially available tablets containing the compound. We also showcase the utility of dynamical refinement to unambiguously assign absolute configuration. The results highlight the immense potential of 3D ED/MicroED for structure elucidation of components of microcrystalline mixtures that obviates the need to grow large-size single crystals and the use of complementary analytical techniques, which could be important for identification as well as for primary structural characterization.

Effectiveness, safety, and tolerability of bilastine 20 mg vs levocetirizine 5 mg for the treatment of chronic spontaneous urticaria: A double-blind, parallel group, randomized controlled trial.

Chronic spontaneous urticaria (CSU) is a debilitating condition, adversely affecting the patient's quality of life. Bilastine is a recently introduced, non-sedative H1-antihistamine for its treatment. We wanted to compare the effectiveness, safety, and tolerability of bilastine 20 mg vs levocetirizine 5 mg in moderate-to-severe CSU. We conducted a double-blind, randomized controlled trial with two groups: bilastine 20 mg (n = 31) and levocetirizine 5 mg (n = 27), once daily for 42 days. We included patients (18-65 years), with moderate-to-severe CSU. UAS7, VAS, and DLQI were used to assess severity of urticaria, global urticaria-induced discomfort and quality of life, respectively. DLQI was assessed at baseline (D0) and end-of-treatment (D42), while UAS7 and VAS were noted at baseline and all follow-up visits. Assessment of UAS7 alteration was our primary objective, while changes in DLQI and VAS were the secondary outcomes. Safety was assessed by recording drug-related adverse events, biochemical investigations, and electrocardiogram, along with tolerability and compliance. Both drugs significantly improved UAS7, DLQI, and VAS at end-of-treatment (D42) compared with baseline (intra-group). At the end-of-treatment, all parameters showed greater improvement with bilastine, but only UAS7 reduction was significant (bilastine > levocetirizine, P = .03). In both the groups, UAS7 and VAS improved significantly D14 onwards, and was maintained throughout the study. Sedation was significantly less with bilastine (P = .04), while neither drug showed any serious adverse-effect. Tolerability of both drugs was similar. Therefore, bilastine was found to be a more effective and less-sedative novel therapy for CSU compared to levocetirizine, with similar effect on quality of life.

Levocetirizine for the treatment of itch in psoriasis patients: An open-label pilot study in a real-world setting.

Itch is the most bothersome symptom in psoriasis, often leading to impaired quality of life. Treatment of psoriasis-induced itch is frequently unsatisfactory as the various therapies employed have a delayed onset of effect. Histamine-1 receptor (H1) antihistamines are not recommended in treatment guidelines as histamine is not considered a key mediator in psoriasis. However, patients using H1 antihistamines frequently report benefits in questionnaire-based studies. To address these contradictions, we examined the short-term effects of levocetirizine, a nonsedating H1 antihistamine, on psoriasis-related itch and itch-related quality of life. In this pilot study, patients with psoriasis-related itch received levocetirizine 5-10 mg daily as a concomitant treatment for 5 days. Change of itch intensity as measured by hourly itch ratings and the change of itch-related quality of life were measured at different time points. A total of 29 of 30 patients (96%) reported a decline in itch within 5 days. Mean itch reduction was 23% after Day 1 (p = .005), 40% after Day 3 (p < .001), and 41% after Day 5 (p < .001). Furthermore, itch-related quality of life also significantly improved after 5 days (p < .001). Only 2 of 30 patients (6.7%) reported mild sleepiness. Levocetirizine 5-10 mg daily as an add-on therapy seems to be an effective treatment to improve itch and itch-related quality of life within only a few days.

Semi-solid extrusion 3D printing ODFs: an individual drug delivery system for small scale pharmacy.

Orodispersible films (ODFs) are promising drug delivery systems for customized medicines as it provide an alternative approach to increase consumer acceptance by advantages of rapid dissolution and administration without water. The aim of this study was to develop a platform to support the realization of tailored treatments suitable for the extemporaneous production of ODFs by semi-solid extrusion (SSE) 3D printing (3DP). Hydroxypropyl methyl cellulose (HPMC) was used as the polymer of ODFs, and levocetirizine hydrochloride was used as the model drug. The optimal formulation was HPMC:API:PS:maltitol:sucralose at a ratio of 64:10:10:15:1. Seventeen percent HPMC solution and optimal formulation were used to prepare film precursors. The impact of dynamic viscosities and fluid mechanics difference on printing applicability was discussed. The ODFs of cube designs with aimed dose of 1.25 mg, 2.5 mg, and 5 mg were printed by SSE 3DP. Good linear relationship between theoretical model volume and drug content (R2 = 0.999) and good dose accuracy indicate that 3DP is a suitable method for preparing individualized ODFs.

The effect of levocetirizine and montelukast on clinical symptoms, serum level and skin expression of COX-1 and COX-2 enzymes in patients suffering from chronic autoimmune urticaria - a pilot study.

INTRODUCTION: Chronic autoimmune urticaria (CAU) lasts over 6 weeks and is characterized by circulating IgE autoantibodies or IgG against IgE or IgE receptor. AIM: To assess the clinical, laboratory and histological effects of 4-week levocetirizine and montelukast therapy in patients suffering from CAU. MATERIAL AND METHODS: Of 296 tested patients with chronic urticaria 40 had a positive ASST test. Only 17 (16 female/1 male; medium age: 44 years) fulfilled all study inclusion/exclusion criteria. The study was designed as an open, randomized trial with two arms: levocetirizine or montelukast treatment for 4 weeks following a 2-week wash-out period. All participants completed urticaria activity score (UAS) and visual analogue scale (VAS) questionnaires before and after both therapies. Blood samples and skin bioptats were obtained before and after treatment to evaluate COX-1 and COX-2 serum concentrations and skin expression. RESULTS: Clinical response to therapy measured with the UAS and VAS was better in the levocetirizine group. Both drugs caused a significant decrease in COX-1 and COX-2 serum level. COX-1 and COX-2 expression in epidermal and dermal inflammatory infiltration did not change significantly in either study group, but a significant decrease of COX-1 expression was observed when the groups were combined for analysis, and the decrease in COX-2 expression in the epidermis was of borderline significance. CONCLUSIONS: The effectiveness of levocetirizine and montelukast in treating CAU may be partly related to the reduction of COX-1 and COX-2 serum level and tissue expression, but further studies on a larger group of patients are needed to support this observation.

Efficacy of Desloratadine and Levocetirizine in Patients with Cedar Pollen-Induced Allergic Rhinitis: A Randomized, Double-Blind Study.

BACKGROUND: No comparative study of antihistamines that differ in structural system has been conducted in allergic rhinitis. OBJECTIVE: This was a randomized, double-blind, crossover comparative study to verify the efficacy of antihistamines that differ in structural system. METHODS: A total of 50 patients with moderate or more severe Japanese cedar pollen-induced allergic rhinitis were randomized to receive either placebo, desloratadine 5 mg (a tricyclic), or levocetirizine 5 mg (a piperazine). One dose of the study drug was orally administered at 9 pm on the day before a pollen exposure test, which was performed for 3 h (9 a.m. to 12 p.m.) to assess symptoms in an environmental challenge chamber (ECC). Nasal and ocular symptoms were compared at an airborne pollen level of 8,000 grains/m3. The primary endpoint was mean total nasal symptom score (TNSS) from 120 to 180 min in the ECC. Subjects with a difference of ≥1 in TNSS between 2 drugs were extracted to the relevant drug-responsive group. RESULTS: The difference in TNSS from placebo was -2.42 (p < 0.0001) with levocetirizine and -1.66 (p < 0.01) with desloratadine, showing that both drugs were significantly more effective than placebo in controlling symptoms, but with no statistically significant difference between the 2 drugs. There were 12 subjects in the desloratadine-responsive group and 24 subjects in the levocetirizine-responsive group, with no contributor to response was detected. CONCLUSION: Levocetirizine tended to control nasal symptoms more effectively than desloratadine. However, the response to each antihistamine varied among individuals and the predictors to the response are unknown. CLINICAL TRIAL REGISTRATION NUMBER: UMIN ID: UMIN000029653.

Simultaneous bioanalysis and pharmacokinetic interaction study of acebrophylline, levocetirizine and pranlukast in Sprague-Dawley rats.

The combination of acebrophylline (ABP), levocetirizine (LCZ) and pranlukast (PRN) is used to treat allergic rhinitis, asthma, hay-fever and other conditions where patients experience difficulty in breathing. This study was carried out with the aim of developing and validating a reverse-phase high-performance liquid chromatographic bioanalytical method to simultaneously quantitate ABP, LCZ and PRN in rat plasma. The objective also includes determination of the pharmacokinetic interaction of these three drugs after administration via the oral route after individual and combination treatment in rat. Optimum resolution between the analytes was observed with a C18 Kinetex column (250 mm × 4.6 mm × 5 µm). The chromatography was performed in a gradient elution mode with a 1 mL/min flow rate. The calibration curves were linear over the concentration range of 100-1600 ng/mL. The intra- and inter-day precision and accuracy were found to be within acceptable limits as specified in US Food and Drug Administration guideline for bioanalytical method validation. The analytes were stable on the bench-top (8 h), after three freeze-thaw cycles, in the autosampler (8 h) and as a dry extract (-80°C for 48 h). The statistical results of the pharmacokinetic study in Sprague-Dawley rats showed a significant change in pharmacokinetic parameters for PRN upon co-administration of the three drugs.

Effects of levocetirizine and diphenhydramine on regional glucose metabolic changes and hemodynamic responses in the human prefrontal cortex during cognitive tasks.

OBJECTIVE: Antihistamines often have sedative side effects. This was the first study to measure regional cerebral glucose (energy) consumption and hemodynamic responses in young adults during cognitive tests after antihistamine administration. METHODS: In this double-blind, placebo-controlled, three-way crossover study, 18 healthy young Japanese men received single doses of levocetirizine 5 mg and diphenhydramine 50 mg at intervals of at least six days. Subjective feeling, task performances, and brain activity were evaluated during three cognitive tests (word fluency, two-back, and Stroop). Regional cerebral glucose consumption changes were measured using positron emission tomography with [18 F]fluorodeoxyglucose. Regional hemodynamic responses were measured using near-infrared spectroscopy. RESULTS: Energy consumption in prefrontal regions was significantly increased after antihistamine administration, especially diphenhydramine, whereas prefrontal hemodynamic responses, evaluated with oxygenated hemoglobin levels, were significantly lower with diphenhydramine treatment. Stroop test accuracy was significantly impaired by diphenhydramine, but not by levocetirizine. There was no significant difference in subjective sleepiness. CONCLUSIONS: Physiological "coupling" between metabolism and perfusion in the healthy human brain may not be maintained under pharmacological influence due to antihistamines. This uncoupling may be caused by a combination of increased energy demands in the prefrontal regions and suppression of vascular permeability in brain capillaries after antihistamine treatment. Further research is needed to validate this hypothesis.

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.

[Allergic rhinitis: the modern aspects of therapy]. / Allergicheskii rinit: sovremennye aspekty terapii.

The main objectives of the present article were to systematize the modern views of the causes and risk factors of allergic rhinitis, to clarify the manner of its development, to define the leading etiological mechanism underling the pathogenesis of this condition, to consider the methods used for the diagnostics and the treatment of this disease, and to sum up the clinical experience with the use of Levocetirizine (Allerwey) for the management of allergic rhinitis. Special attention is given to the achievement and the maintenance of control of the persistent or intermittent forms of allergic rhinitis and to approaches to its treatment based on the medications registered in the Russian Federation.

Effects of Rupatadine on Platelet- Activating Factor-Induced Human Mast Cell Degranulation Compared With Desloratadine and Levocetirizine (The MASPAF Study).

BACKGROUND AND OBJECTIVE: Platelet-activating factor (PAF) is a lipid mediator involved in the pathophysiology of several allergic diseases, for example, in the amplification of mast cell (MC) activation in anaphylaxis. Rupatadine is an antihistamine with a demonstrated anti-PAF effect, although its capacity to inhibit PAF-induced MC degranulation has not been fully evaluated. Objectives: To compare the ability of rupatadine to inhibit PAF-induced MC degranulation with that of desloratadine and levocetirizine and to confirm the dual anti-H1 and anti-PAF activity of rupatadine. METHODS: The human MC line LAD2 and primary MCs (human lung tissue MCs [hLMCs]) were used. MC mediator release was evaluated using the b-hexosaminidase and histamine release assay. The effects of rupatadine (H1 antagonist + PAF receptor antagonist), desloratadine, and levocetirizine (H1 antagonists) on LAD2 and hLMCs were compared. The PAF receptor antagonists WEB2086, BN52021, and CV6209 were also tested. PAF receptor protein expression was evaluated in both LAD2 and hLMCs. RESULTS: CV6209 and rupatadine inhibited PAF-induced MC degranulation in both LAD2 and hLMCs. In LAD2, rupatadine (5 and 10 µM) and levocetirizine (5 µM), but not desloratadine, inhibited PAF-induced b-hexosaminidase release. Rupatadine (1-10 µM), levocetirizine (1-10 µM), and desloratadine (10 µM) inhibited PAF-induced histamine release. Rupatadine at 10 µM had an inhibitory effect on hLMC degranulation, but levocetirizine and desloratadine did not. CONCLUSIONS: This study shows that rupatadine and, to a lesser extent, levocetirizine, but not desloratadine, inhibit PAF-induced degranulation in both LAD2 and hLMCs. These findings support the dual antihistamine and anti-PAF effect of rupatadine in allergic disorders.

Effects of ICI204,448, naloxone methiodide and levocetirizine on the scratching behavior induced by a κ-opioid antagonist, nor-BNI, in ICR mice.

OBJECTIVE: In this study, we aimed to study the effects of ICI204,448, naloxone methiodide and levocetirizine on the scratching behavior induced by intradermal injection of a ?-opioid antagonist, nor-binaltorphimine (nor-BNI), into the rostral back of ICR mice were investigated. MATERIALS AND METHODS: Male ICR mice weighing 30?35 g were used. The number of scratching episodes were counted for 60 min after i.d. injection of nor-BNI. RESULTS: nor-BNI dose dependently increased in the number of scratching episodes in ICR mice. nor-BNI-induced scratching behavior was inhibited by not only nalfurafine but also ICI204,448, a peripherally selective ?-opioid agonist. Naloxone and naloxone methiodide, a peripherally restricted ?-opioid antagonist, also inhibited nor-BNI-induced scratching behavior. Scratching behavior induced by nor-BNI was inhibited by chlorpheniramine as well as levocetirizine, a third-generation H1 antagonist that does not cross into the CNS. CONCLUSION: These results suggest that scratching behavior induced by this ?-opioid antagonist, nor-BNI, is related to not only central but also peripheral opioid and H1 receptors.

CRP, D-dimer, fibrinogen and ESR as predictive markers of response to standard doses of levocetirizine in patients with chronic spontaneous urticaria.

SUMMARY: According to current guidelines, non-sedative H1-antihistamines (nsAH) are the first-line therapy of chronic spontaneous urticaria (CSU). But even up-dosed antihistamines (to four times the standard dose) produce symptom resolution in less than 50% of patients. Biomarkers that can predict the response to nsAH are still unknown. We carried out a prospective study and used discriminant analysis to evaluate the combination of D-dimer, fibrinogen, C-reactive protein and ESR values for predicting the outcome of treatment with levocetirizine in 84 CSU patients. We found that elevation of these parameters is associated with more active disease, low quality of life and lack of response to standard doses of levocetirizine. Thus, evaluation of these markers may be considered useful before starting treatment with nsAH. The mechanisms behind the increase in these parameters in CSU patients need to be elucidated in further studies.

Label-free versus conventional cellular assays: Functional investigations on the human histamine H1 receptor.

A set of histamine H1 receptor (H1R) agonists and antagonists was characterized in functional assays, using dynamic mass redistribution (DMR), electric cell-substrate impedance sensing (ECIS) and various signaling pathway specific readouts (Fura-2 and aequorin calcium assays, arrestin recruitment (luciferase fragment complementation) assay, luciferase gene reporter assay). Data were gained from genetically engineered HEK293T cells and compared with reference data from GTPase assays and radioligand binding. Histamine and the other H1R agonists gave different assay-related pEC50 values, however, the order of potency was maintained. In the luciferase fragment complementation assay, the H1R preferred ß-arrestin2 over ß-arrestin1. The calcium and the impedimetric assay depended on Gq coupling of the H1R, as demonstrated by complete inhibition of the histamine-induced signals in the presence of the Gq inhibitor FR900359 (UBO-QIC). Whereas partial inhibition by FR900359 was observed in DMR and the gene reporter assay, pertussis toxin substantially decreased the response in DMR, but increased the luciferase signal, reflecting the contribution of both, Gq and Gi, to signaling in these assays. For antagonists, the results from DMR were essentially compatible with those from conventional readouts, whereas the impedance-based data revealed a trend towards higher pKb values. ECIS and calcium assays apparently only reflect Gq signaling, whereas DMR and gene reporter assays appear to integrate both, Gq and Gi mediated signaling. The results confirm the value of the label-free methods, DMR and ECIS, for the characterization of H1R ligands. Both noninvasive techniques are complementary to each other, but cannot fully replace reductionist signaling pathway focused assays.