To elucidate the effects of
corticosteroids on nonspecific bronchial reactivity in asthmatic children, inhaled challenges with
methacholine were conducted in 10 atopic asthmatic subjects (9 to 15 yr of age) before and after consecutive week-long trials of daily orally administered placebo and
prednisone (60 mg/day). Pharmacologic bronchial sensitivity was evaluated as the log dose of
methacholine producing a 20% fall in FEV1 (PD20-FEV1). The week-long trial of placebo had no effect on either baseline lung function or PD20-FEV1. On the other hand, after the 1-wk course of
prednisone: (1) both baseline FEV1 and FEF25-75 systematically improved in the patients who initially had (i.e., before
prednisone) lower values, and (2) PD20-FEV1 significantly increased (p less than 0.001) in all the subjects studied. The magnitude of increase in PD20-FEV1 after
prednisone was significantly inversely related (i.e., inverse hyperbola) to the initial degree of
airway obstruction (i.e., FEV1) obtained prior to
prednisone treatment. Moreover, whereas 6 of 10 patients only minimally changed their baseline FEV1 after
prednisone, collectively for all the subjects, the percent increase in PD20-FEV1 after
prednisone was directly related (correlation coefficient, 0.70; p less than 0.05) to the corresponding percent increase in baseline FEV1 after
prednisone. These findings demonstrate that after a week-long course of high-dose
prednisone therapy: (1) a significant reduction occurs in bronchial sensitivity to inhaled
methacholine in the asthmatic child, and (2) the degree of diminution in airway sensitivity to
methacholine is inversely related to the patient's baseline status of
airway obstruction.