Treatment for allergic rhinitis and chronic idiopathic urticaria: Focus on oral antihistamines

OBJECTIVE: To review the efficacy and safety of first- and newer-generation antihistamines for the management of allergic rhinitis and chronic idiopathic urticaria (CIU), with a focus on management in the pharmacy. DATA SOURCES: A literature review was performed using MEDLINE (1966-October 2005), with no time or language restrictions. Key words or phrases used were histamine, antihistamine(s), first- and second-generation, allergic rhinitis, chronic idiopathic urticaria, quality of life, impairment, sedation, cost-effectiveness, astemizole, cetirizine, desloratadine, diphenhydramine, fexofenadine, loratadine, hydroxyzine, ketotifen, and mizolastine. Additional references were found in the bibliographies of the articles cited. STUDY SELECTION AND DATA EXTRACTION: Clinical trials and other experimental studies of the use of antihistamines for the management of allergic rhinitis and CIU were selected. Review papers and guidelines were also included. DATA SYNTHESIS: First-generation antihistamines are effective at ameliorating the symptoms of allergic rhinitis and CIU; however, they are associated with adverse effects due to a lack of selectivity for the histamine H₁-receptor and an ability to bind to cerebral H₁-receptors. Newer-generation agents, in general, possess high H₁-receptor selectivity and a low tendency to cross the blood-brain barrier, while maintaining efficacy. In general, safety at elevated doses has been demonstrated for the newer antihistamines, although higher rates of sedation and impairment have been reported with increasing doses for some agents. CONCLUSIONS: Pharmacists can play an important role in the management of allergic rhinitis and CIU by considering the relative advantages of newer-generation agents when reviewing treatment options.