Cetirizine: a unique second-generation antihistamine for treatment of rhinitis and chronic urticaria.

The recent development of selective H1-antagonists that minimally cross the blood-brain barrier has greatly improved the management of allergic rhinitis and chronic urticaria. These new agents have much reduced anticholinergic and sedative side effects, which were the major drawbacks of the classic H1-antihistamines. Cetirizine, a new second-generation H1-antagonist, offers several properties that may further improve the treatment of allergic rhinitis and chronic urticaria. Cetirizine is the only antihistamine known to possess activity against both the histamine-mediated early phase of the allergic response and the late-phase response of immediate hypersensitivity characterized by migration of inflammatory cells to the site of the reaction. Its efficacy has been demonstrated in clinical trials of patients with seasonal rhinitis and urticaria. The most common side effects associated with cetirizine, such as sedation, are similar to those of other second-generation antihistamines. These properties, combined with a once-daily dosage regimen, should help improve patient compliance and optimize antihistamine therapy.