Cetirizine: antiallergic therapy beyond traditional H1 antihistamines.

For three decades, traditional H1 antihistamines have been used in the treatment of allergic diseases. They are effective in reducing histamine-related symptoms, but the use of such agents has been limited by sedation and anticholinergic side effects. These adverse effects are fewer with the recently introduced H1 antihistamines. One of these, cetirizine, a human metabolite of hydroxyzine, is characterized by its high selectivity for the H1 receptor site and its reliable and consistent inhibition of histamine-induced allergic reactions. It also blocks eosinophil infiltration to the site of allergen-induced cutaneous reactions. Cetirizine has proved effective in the treatment of seasonal and perennial allergic rhinitis and urticaria. It is excreted primarily by renal mechanisms. It is well tolerated by elderly patients. Cetirizine has a low rate of penetration of the blood-brain barrier, and it has minimal central nervous system impairment. Furthermore, it can be given once a day. Cetirizine's low incidence of sedation and anticholinergic side effects contribute to its high profile of safety. In this article the characteristics, pharmacology, pharmacokinetics, and mode of action of cetirizine are reviewed.