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.