Long-term oral bronchodilator therapy of asthma with pirbuterol.

We studied the effects of an oral beta2 selective bronchodilator, pirbuterol, in 12 male asthmatic patients over periods ranging from 6 to 23 months (mean, 13.8). Each patient was evaluated initially by physical examination, urinalysis, blood analysis, and pulmonary function tests. Patients were examined at regular intervals thereafter. Patients remained off all bronchodilator therapy for 12 hr before each visit. Blood analysis, urinalysis, and pulmonary function tests were performed and the pulmonary function tests were repeated approximately 2 hr after an oral dose of pirbuterol. We found no significant changes in the baseline resistance or in the bronchodilator response to pirbuterol during the course of the study, but there was a significant decrease in the functional residual capacity (FRC). The reduction in FRC could be due to the prolonged reduction in airways resistance with continuous therapy. We found no increase in the bronchodilator response to pirbuterol during oral prednisone therapy. There were no significant changes in serum potassium. Side effects attributable to pirbuterol, nervousness and tremor, occurred in only 2 patients and were easily controlled.