Theophylline in chronic obstructive pulmonary disease.

Although prolonged use of maintenance theophylline therapy in chronic obstructive lung disease remains controversial, evidence from well-designed studies indicates that it produces patient improvement as gauged by both objective and subjective measurements. An important reason to use sustained-release theophylline is to prevent episodes of bronchospasm by providing a smooth around-the-clock bronchodilator effect and thus reducing the need for periodic aerosolized beta agonists. Theophylline also increases diaphragmatic contractility and endurance, although there is disagreement concerning the practical clinical significance of this effect. The drug improves cardiovascular function by increasing myocardial contractility and by reducing pulmonary and systemic vascular resistances. The increased central respiratory drive produced by theophylline may be important in reducing the ventilatory depressant effects of oxygen therapy. The drug also acts to inhibit mediator release and improves several aspects of mucociliary function, although, again, the clinical significance of these actions has not been established.