Effect of theophylline on improvement of the pulmonary function in the treatment of acute episodes of asthma: the influence of the severity of acute asthma.

The bronchodilating effect of theophylline was studied from the perspective of its influence on the severity of acute asthmatic attack and where its acting site is located on bronchi. Pulmonary function including maximal expiratory flow-volume curve breathing of room air and of a gas mixture containing 80% helium and 20% oxygen (He-O2) was measured at each incremental plasma theophylline concentration plateau (5, 10, and 15 micrograms/mL) in 12 acutely ill asthmatic patients. Before starting the administration of theophylline, clinical findings were used to classify the severity of the asthmatic attack into mild, moderate, or severe groups. Our data suggested that theophylline acts on both the central and peripheral airways and that theophylline improves the airway obstruction in a dose-dependent fashion when the severity of acute attack is mild.