Isoproterenol challenge during placebo and oral theophylline therapy in chronic obstructive pulmonary disease.

Because it is common to perform a bronchodilator challenge while a patient continues oral methylxanthines, we wanted to determine if this procedure might be misleading for subsequent therapy. Thirty-eight men with a long smoking history and a clinical diagnosis of chronic obstructive pulmonary disease (COPD) were given placebo and oral theophylline (each for one month) in a double-blind, single-crossover manner. Pulmonary functional tests were performed before and after isoproterenol nebulization on the final day of each 4-wk period. There were significantly larger increases in FVC (p less than 0.001) and FEV1 (p less than 0.01) after isoproterenol challenge when receiving placebo than when receiving theophylline. According to the intermountain Area rating criteria, only the results after isoproterenol challenge during placebo therapy would indicate improvement. These results suggested that isoproterenol inhalation challenge be performed after methylxanthines have been discontinued if used to predict which patients with COPD may respond to oral theophylline therapy.