Nonsedating H1 antihistamines in chronic urticaria.

Histamine type 1 (H1) receptor antagonists are the principal therapy for chronic urticaria. Their usefulness, however, is sometimes compromised by undesirable central nervous system (CNS) side effects such as daytime sedation and anticholinergic side effects such as dry mouth. Second-generation, nonsedating antihistamines (terfenadine, astemizole, loratadine, and cetirizine hydrochloride) are just as effective as the potent first-generation antihistamines such as hydroxyzine. Yet they do not cause the CNS and anticholinergic side effects seen with the older agents. Cardiovascular side effects, which have been recently reported with terfenadine and astemizole, are dose related and rare, generally occurring in patients who overdose or who take concomitant medications that increase serum antihistamine levels. The second-generation antihistamines also offer twice daily and once daily dosage schedules, which are more convenient than the two- to four-times daily schedules of the older agents. They should therefore be considered first-line agents for the treatment of chronic urticaria. This article is a review of the role of the nonsedating antihistamines in the treatment of chronic urticaria.