Antihistamine- and decongestant-induced performance decrements.

Among the most common of health problems, allergies afflict more than one of every six Americans. In the allergic reaction, mast cells degranulate, releasing inflammatory mediators such as histamine. These mediators in turn cause smooth muscle contraction, itch, mucus secretion, and vascular leakage. A number of pharmacologic agents, including the H1 receptor antihistamines and the sympathomimetic decongestants, have been developed in an attempt to minimize such effects. Antihistamines were first used clinically 50 years ago. Currently taken by approximately 30 million Americans each year, they are grouped by structure into six classes. Until recently, all of the classes, or first-generation antihistamines, were thought to be relatively equal in efficacy and, because of their ability to cross the blood-brain barrier, they all caused varying degrees of sedation. The effects of antihistamines on psychomotor reflexes and driving skills, antihistamine-induced drowsiness, and the interaction of antihistamines with alcohol and tranquilizers are reviewed. The centrally acting first-generation agents, and the performance decrements these agents commonly induce, are compared with the newer, nonsedating, second-generation antihistamines (eg, terfenadine, astemizole, cetirizine, and loratadine). Although decongestants do not appear to cause impaired performance, this needs to be evaluated further, particularly with regard to decongestant-induced insomnia.