Methylxanthine therapy and reversible airway obstruction.

Theophylline is a medium-potency bronchodilator that is useful in the treatment of reversible airway obstruction from any cause. It also improves contraction of the diaphragm, accelerates mucociliary transport, lowers pulmonary artery pressures, and limits the release of the mediators of immediate hypersensitivity from mast cells. The pharmacologic effects correlate closely with the plasma concentration of this drug, and within the defined therapeutic limits, only minor adverse effects occur. The dose of theophylline required to achieve therapeutic plasma levels varies considerably between subjects, mainly because of differences in clearance. The latter varies with age, smoking, alterations in hepatic function, cardiac failure, viral infections, and concurrent administration of other drugs. For the treatment of acute symptoms, either intravenous administration or a rapidly absorbed compound such as uncoated tablets or liquids is required. For the long-term management of reversible airway obstruction, sustained-release theophyllines are available. These formulations maintain therapeutic serum theophylline concentrations for prolonged periods, permitting longer dosing intervals and improved patient compliance.