Vivian P Hernandez TrujiUo md and Phil Lieberman md

Contents

Histamine

Classical, First-Generation Antihistamines Second-Generation Antihistamines Suggested Reading summary

Histamine is widely distributed throughout the body, with the highest concentrations in the lung, skin, and gastrointestinal tract. H1 receptors are the most important in producing allergic symptoms. Most first-generation antihistamines have a structural resemblance to histamine. The most important side effect of first-generation antihistamines is sedation. As a consequence, increasing numbers of second-generation antihistamines have become available. The activities of second-generation antihistamines are probably related to the fact that each of these mediators act through a G proteincoupled receptor that is analogous in structure to the receptor for histamine. The advantages of second-generation antihistamines include lack of sedation and ease of use (i.e., once-daily dosing). Antihistamines are important in the treatment of various allergic diseases. Antihistamines are the first-line therapy in the treatment of allergic rhinitis. Antihistamines are also becoming increasingly important in the treatment of urticaria, atopic dermatitis, and asthma. The use of antihistamines will likely expand as research into their use continues.

Key Words: Antihistamines; second generation, nonsedating; allergic rhinitis; allergies; treatment.

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