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Concept: Histamine antagonist


Background  Recently, the updated EAACI/GA(2) LEN/EDF/WAO guidelines for urticaria have been published. Objective  To examine how chronic spontaneous urticaria (csU) patients in Germany are diagnosed and treated, and to compare the outcome to the guideline recommendations. Methods  During this cross-sectional survey study, most dermatologists, paediatricians and 5149 general practitioners in private practice in Germany were asked to participate. All physicians who agreed were requested to complete a standardized questionnaire about their diagnostic and therapeutic management of csU. Results  A total of 776 questionnaires were available for analysis. Most physicians (82%) were attempting to identify underlying causes in their csU patients, but with only limited success. More than 70% reported to check for total serum IgE and to do skin prick testing (not suggested in first line by guideline). In contrast, only 10% applied the autologous serum skin test. The most common first-line treatments were non-sedating antihistamines in standard or higher doses (as recommended). However, many physicians reported still using first generation sedating antihistamines (23%) (not recommended) or systemic steroids (18%). Experience with alternative options was low. Less than one-third of the participants reported to be familiar with the guidelines. Those who did, were found to be more likely to check for underlying causes, to be more experienced with antihistamine updosing and to be more reluctant to use sedating antihistamines or systemic steroids. Conclusion  The diagnostic and therapeutic management of csU by private practice physicians does not sufficiently comply with the guidelines. Awareness of the guidelines can lead to improved care.

Concepts: Medicine, Physician, Histamine, General practitioner, Questionnaire, H1 antagonist, Histamine antagonist, Antihistamines


Introduction: Urticaria is a highly prevalent disease among people. First-choice treatment continues to be centred on the second-generation H1 antihistamines, including a wide group of drugs with a better therapeutic index (or risk:benefit ratio) than the classic ones, even in the high, off-label dosage occasionally required in chronic urticaria. Bilastine is a newly registered H1-antihistamine for treatment of allergic rhinoconjunctivitis and urticaria. With established antihistaminic and antiallergic properties, it is widely reviewed in the medical literature; however, to our knowledge, a specific review of bilastine’s role in the treatment of urticaria was lacking. Areas covered: This article reviews the medical literature on the effectiveness and safety of bilastine in urticarial syndromes, either spontaneous or inducible, by means of a Medline search from 1990 to present, completed with some nonpublished data provided by the manufacturer. Expert opinion: Once-daily treatment with bilastine 20 mg is effective in managing symptoms and improving patient’s quality of life in chronic urticaria, with at least comparable efficacy to levocetirizine. As far as studies in healthy volunteers, clinical assays, and recent clinical experience can establish, bilastine’s safety profile is adequate, appearing to be entirely free from cardiovascular effects, and not impairing psychomotor performance or actual driving, even at twice the therapeutic dose.

Concepts: Pharmacology, Medicine, Asthma, Effectiveness, Efficacy, Urticaria, H1 antagonist, Histamine antagonist


OBJECTIVE: Recent evidence indicates that antihistamines can affect movement, which is most likely due to altered neurotransmission in cholinergic and histaminergic pathways. The purpose of this study was to determine if antihistamines with varying anticholinergic properties differentially affect voluntary and involuntary movement control. METHODS: Eleven healthy subjects were enlisted into a human double blind, placebo-controlled, five-way crossover study. Drowsiness, reaction time, and physiological tremor were examined 1-, 2-, and 3-hr post-ingestion of antihistamines with known anticholinergic profiles. These were the first-generation promethazine, and second-generation loratadine, desloratadine, and fexofenadine. Hyoscine butylbromide was used in an additional experiment to determine how a peripheral antimuscarinic drug influenced neuromotor function. RESULTS: Promethazine, desloratadine and fexofenadine increased drowsiness. Promethazine increased simple and choice reaction time and reduced tremor. Desloratadine increased choice reaction time and tremor, while loratadine slowed simple and choice reaction time. CONCLUSION: Central anticholinergic and antihistaminergic properties of antihistamines potentially contribute to movement dysfunction. SIGNIFICANCE: Second-generation antihistamines have provided the consumer with a safer alternative to the first-generation sedating antihistamine. However, the results of this study suggest that loratadine and desloratadine have the potential to affect movement control, and further research is warranted to understand the clinical relevance of these findings.

Concepts: Crossover study, Histamine, Anticholinergic, H1 antagonist, Histamine antagonist, Antihistamines, H1 receptor antagonists, Scopolamine


Abstract Background: Levocetirizine and desloratadine are mostly used H1-antihistamines in the treatment of allergic disease in 5 mg and 10 mg doses. Objective: In this study, the efficacy of single oral dosages of 5 mg and 10 mg desloratadine and levocetirizine were compared by using histamine-induced wheal and flare reactions. Methods: Eighty healthy volunteers were randomized for 4 double blinded treatment with desloratadine 5 mg-10 mg, levocetirizine 5 mg-10 mg. Wheal and flare responses were produced by histamine. Measurements were performed just before the ingestion of antihistamines (baseline) and afterwards at 30, 60, 240 minutes and 24 hours. The values obtained for each antihistamine were compared with baseline values. Results: It was found that, except the flare reactions at 30th minute, levocetirizine 5 mg and 10 mg suppressed histamine-induced wheal-flare reactions more than desloratadine 5 mg and 10 mg did. There were not any significant differences between desloratadine 5 mg and 10 mg in all periods. Levocetirizine 10 mg suppressed wheal-flare reactions significantly more than levocetirizine 5 mg only at 24th hour. Conclusion: In this study it was observed that levocetirizin 5 mg and 10 mg has a higher activity than desloratadine’s.

Concepts: Allergy, Dose, Histamine, Harshad number, H1 antagonist, Histamine antagonist, Antihistamines


A slow response to omalizumab (anti-IgE) in CSU patients is strongly correlated with IgG-anti-FcεRI-mediated serum-induced basophil histamine release suggesting that, in these patients, effects on FcεRI are critical for the mechanism of action of omalizumab.

Concepts: Asthma, Mast cell, Histamine, Histamine antagonist


Introduction: Approximately 10 - 15% of women reportedly take an antihistamine during pregnancy for the relief of nausea and vomiting, allergy and asthma symptoms, or indigestion. Antihistamines include histamine H1-receptor and H2-receptor antagonists. Areas covered: This is a systematic evaluation of the peer-reviewed epidemiologic literature published through February 2014 on the association between prenatal exposure to antihistamines and birth defects. Papers addressing histamine H1- or H2-receptor antagonists are included. Papers addressing pyridoxine plus doxylamine (Bendectin in the United States, Debendox in the United Kingdom, Diclectin in Canada, Lenotan and Merbental in other countries) prior to the year 2001 were excluded post hoc because of several previously published meta-analyses and commentaries on this medication. Expert opinion: The literature on the safety of antihistamine use during pregnancy with respect to birth defects is generally reassuring though the positive findings from a few large studies warrant corroboration in other populations. The findings in the literature are considered in light of three critical methodological issues: i) selection of appropriate study population; ii) ascertainment of antihistamine exposures; and iii) ascertainment of birth defect outcomes. Selected antihistamines have been very well studied (e.g., loratadine); others, especially H2-receptor antagonists, require additional study before an assessment of safety with respect to birth defect risk could be made.

Concepts: Epidemiology, Evaluation, United States, United Kingdom, Histamine, Histamine antagonist, Histamine H1 receptor, Daubert v. Merrell Dow Pharmaceuticals


Antivenoms or antitoxins have been effectively used for more than a century. During this time, these products have always proven to be highly effective in the treatment of infections and envenomations. However, antivenoms did not exhibit good safety results in their initial applications. After many improvements, antivenoms have substantially better safety profiles but still have some side effects. Due to the occurrence of adverse reactions, the practice of using premedication with the intent to decrease side effects has become accepted or mandatory in many countries. The drugs used for premedication belong to the histamine H1 antagonist, glucocorticoid and catecholamine groups. Currently, this practice is being questioned due to low or controversial efficacies in clinical assays. In this article, we discuss the causes of adverse reactions, the mechanisms of drugs that block the undesired effects and the results obtained in clinical trials. Although these three families of drugs could have positive effects on reducing adverse reactions, only adrenaline has demonstrated positive results in clinical assays.

Concepts: Immune system, Pharmacology, Clinical trial, Effectiveness, Efficacy, Norepinephrine, Histamine antagonist, Histamine receptor


Research indicates that first-generation antihistamine usage may impair pilot performance by increasing the likelihood of vestibular illusions, spatial disorientation, and/or cognitive impairment. Second- and third-generation antihistamines generally have fewer impairing side effects and are approved for pilot use. We hypothesized that toxicological findings positive for second- and third-generation antihistamines are less likely to be associated with pilots involved in fatal mishaps than first-generation antihistamines.

Concepts: Regression analysis, Econometrics, Histamine, Poisson regression, H1 antagonist, Histamine antagonist, Aviator, Antihistamines


In a recent high throughput analysis to identify drugs that alter hepatic apolipoprotein A-I (apo A-I) expression, histamine receptor one (H1) antagonists emerged as potential apo A-1 inducing drugs. Thus the present study was undertaken to identify some of the underlying molecular mechanisms of the effect of antihistaminic drugs on apo AI production. Apo A-I levels were measured by enzyme immunoassay and Western blots. Apo A-I mRNA levels were measured by reverse transcription real-time PCR using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA as the internal control. The effects of histamine and antihistamines on apo A-I gene were determined by transient transfection of plasmids containing the apo A-I gene promoter. Histamine repressed while (H1) receptor antagonist azelastine increased apo A-I protein and mRNA levels within 48h in a dose-dependent manner. Azelastine and histamine increased and suppressed, respectively, apo A-I gene promoter activity through a peroxisome proliferator activated receptor α response element. Treatment of HepG2 cells with other H1 receptor antagonists including fexofenadine, cetirizine, and diphenhydramine increased apo A-I levels in a dose-dependent manner while treatment with H2 receptor antagonists including cimetidine, famotidine, and ranitidine had no effect. We conclude that H1 receptor signaling is a novel pathway of apo A1 gene expression and therefore could be an important therapeutic target for enhancing de-novo apo A-1 synthesis.

Concepts: DNA, Gene, Gene expression, Transcription, Molecular biology, RNA polymerase, Histamine, Histamine antagonist


The humoral IgA is an immunoglobulin which plays a defensive role for organisms on mucosal surfaces. Today, intranasal antihistamines are effectively used in the treatment of allergic rhinitis. In our study, the effect of azelastine hydrochloride-a nasal antihistaminic-on humoral IgA of the nasal mucosa has been reviewed empirically. Twenty-four female Sprague-Dawley rats were included in our study. The rats were divided into three groups randomly. Group 1(azelastine hydrochloride): rats in this group had nasal azelastine hydrochloride (0.05%) applied for 30 days at 10 µl/nostril dosage. Group 2 (saline): saline (0.09%) was applied to the rats in this group for 30 days at 10 µl/nostril dosage. Group 3 (control): no application was made throughout the study. The chemicals applied in Groups 1 and 2 were applied to both nostrils by mounting a flexible micropipette to the end of an insulin injector. At the beginning of the study, nasal lavage was performed to both nostrils of the rats in every group on the 15th and 30th day to aspirate irrigation solution (distilled water). The aspirated liquids were kept at - 80° temperature and reviewed together at the end of study. Within-group comparisons: in Group 1 (azelastine hydrochloride), the humoral IgA value on the 15th day was significantly higher than the basal value (p = 0.037). There is a significant difference between humoral IgA value on the 30th day and humoral IgA value on the 15th day (p = 0.045). In Group 2 (saline), no significant difference is available between basal, 15th day and 30th day humoral IgA values (p = 0.265). In Group 3 (control), no significant difference is available between basal, 15th day and 30th day humoral IgA values (p = 0.374). Between-group comparison: there is no significant difference in between-group humoral IgA basal values (p = 0.714). On days 15 and 30, Humoral IgA value of Group 1 was significantly higher than that of Groups 2 and 3 (p = 0.013, p = 0.024, respectively). According to the results we achieved in our study, nasal antihistaminic (azelastine hydrochloride) significantly increases the level of humoral IgA. Our study is the first one in the literature to reveal a relation between nasal antihistaminic and humoral IgA and there is a further need for clinical, randomized and prospective studies.

Concepts: Immune system, Immunoglobulin A, Touring car racing, Histamine, Mucus, Rhinitis, Histamine antagonist, Antihistamines