Clinical expression of bronchial hyperreactivity in children.

Airway hyperreactivity is a consistent finding in most children with asthma and is responsible for many clinical manifestations of asthma. BH in children has been elicited by bronchial challenge with methacholine and histamine, cold air (isocapnic hyperventilation), and exercise. Pharmacologic agents employed in therapy of childhood asthma, which may modulate both the late asthmatic reaction and bronchial hyperreactivity, include cromolyn sodium, glucocorticoids, and possibly ketotifen. Beta adrenergic agonists, though effectively blocking the early asthmatic response, had no effect on the late response and did not alter bronchial hyperreactivity. Theophylline, in both children and adults, and enprophylline (not yet studied in children) may modify both the early and late responses, but do not appear to have an effect on bronchial hyperreactivity. New drugs that may have potential value in reducing bronchial hyperreactivity include calcium channel blockers and PAF antagonists.