Treating allergic rhinitis with second-generation antihistamines.

Allergic rhinitis afflicts close to 40% of the nation's population and costs more than $1.8 billion a year. The toll exacted by this disorder has been greatly alleviated by nonsedating second-generation antihistamines loratadine, terfenadine, and astemizole. The three agents effectively reduce symptoms without the sometimes intolerable adverse effects of older drugs, but they are not completely equivalent. For example, terfenadine requires twice/day dosing, whereas the others can be given once/day. Astemizole has a slow onset and extremely prolonged duration of action. Both terfenadine and astemizole may have cardiotoxic effects (e.g., torsades de pointes) when serum concentrations rise due to overdosing or drug interactions. Cetirizine, a recently approved second-generation antihistamine, has sedative and anticholinergic effects, although to a lesser degree than the first-generation antihistamines.