Efficacy of Second-Generation Antihistamines in Patients with Allergic Rhinitis and Comorbid Asthma

Background and aims. Allergic rhinitis (AR) and asthma share common mediators, cytokines, and chemokines from mast cells and basophils that are central to the complex cascade of events involved in the inflammatory response. Histamine is the salient mediator released after immunologic challenge, initiating multiple pathologic processes of the allergic reaction that result in bronchial smooth muscle contraction, vasodilation, mucus hypersecretion, and edema. The recent identification of a fourth histamine receptor has reinforced clinical interest in the pleiotropic effects of histamine and the relative roles of histamine receptors in mediating immune and inflammatory responses. Material and methods. A comprehensive literature search was conducted for the following terms, alone or in combination: allergic rhinitis, asthma, antihistamines, histamine, and histamine receptors, and for the second-generation antihistamines azelastine, cetirizine, desloratadine, ebastine, fexofenadine, levocetirizine, loratadine, mizolastine, and rupatadine. Clinical trials were included that reported results for patients with AR and comorbid asthma who were treated with second-generation antihistamines. The search dates ranged from 1995 through 2010. Clinical studies that were not placebo controlled or double blinded were excluded from this review. Results. A total of 14 clinical trials of second-generation nonsedating antihistamines were included in this review. Conclusion. H1-antihistamines have been shown to attenuate the symptoms associated with early- and late-phase allergic reactions. Cumulative clinical evidence indicates that H1-antihistamines may have a beneficial effect on asthma symptoms and improve quality of life. Scientific significance. Mechanistic and clinical data suggest that the potential of H1-antihistamines to alleviate comorbid asthma symptoms in AR patients should be further investigated.