Use of Antihistamines in Allergic Rhinitis

Abstract

Allergic rhinitis is a common immun-mediated inflammatory condition of the nasal mucosa. AR occurs because of the cross linking of IgE by allergens within the upper respiratory tract. Allergy is now understood to be a systemic inflammatory disease. The symptoms caused by this allergic inflammation include sneezing, rhinorrhea, nasal pruritus, and nasal congestion; allergic conjunctivitis often accompanies AR. The interaction of histamine with the histamine H1 receptor, mediates a diversity of classical pathophysiological effects, including nasal blockage, sneezing, itching and rinorrhoea in allergic disease. Antihistamines are very important to the management of allergic disease. They can be classified in three groups. First Generation antihistamines: Promethazine, ketotifen, hydroxyzine, chlorpheniramine, deschlorpheniramine, tripelennamine, oxatomide, cyproheptadine, diphenhydramine. The use of the first-generation antihistamines is considerably limited by their sedative and anticholinergic effects.Second Generation antihistamines: Cetirizine, Loratadine, Mizolastine, ebastine, terfenadine, astemizole, acrivastine, azelastine. The second-generation antihistamines have significantly fewer undesirable CNS and anticholinergic effects than first-generation. New Generation antihistamines: Fexofenadine, levocetirizine, desloratadine, rupatadine. Because of reported cardiac toxicity related to terfenadine and astemizole, new generation antihistamines have been developed. Second and new generation antihistamines are a highly efficacious, fast-acting, and safe therapy for AR in the light of the results of the controlled clinical trials.

Why are second-generation H1-antihistamines minimally sedating?

“…H 1 -antihistamines are the mainstays in the treatment of allergic disorders, particularly seasonal rhinitis, conjunctivitis, urticaria, dermatitis, and asthma Holgate et al, 2008;Pata et al, 2008). Classical (first-generation) H 1 -antihistamines have much stronger sedative effects, e.g., drowsiness, somnolence, fatigue, impairment of cognitive function, memory, and psychomotor performance than second-generation H 1 -antihistamines (Church et al, 2010).…”