Treatment of urticaria and angioedema: low-sedating H1-type antihistamines.

H1-type antihistamines are considered the therapeutic agents of choice for treating urticaria and angioedema. The use of traditional H1 antihistamines is limited by their side effects. In recent years low-sedating H1 antihistamines with reduced sedative and anticholinergic side effects have become popular choices for the treatment of urticaria and angioedema. Terfenadine and astemizole are currently available in the United States, and cetirizine and loratadine, currently under review at the Food and Drug Administration, are available in other countries. Terfenadine, cetirizine, and loratadine achieve rapid peak plasma concentrations in 1 to 2 hours, whereas astemizole has a slow onset of action. In double-blind, placebo-controlled studies of chronic idiopathic urticaria, low-sedating H1 antihistamines were more effective than placebo. The choice of a particular low-sedating H1 antihistamine depends on pharmacokinetic considerations and frequency of administration.