Theophylline and Mucociliary Clearance

¹ Chief of Medicine, Olive View Medical Center; Professor of Medicine, UCLA School of Medicine, Los Angeles.

Multiple sites of action and several different mechanisms appear to be involved in the improved mucociliary clearance seen after giving a variety of drugs. It can be concluded that theophylline enhances clearance through a similar multiplicity of mechanisms involving improvement in the quality and quantity of mucus produced, the increased transfer of fluid across the respiratory epithelium, the stimulation of ciliary activity, and the reduction of bronchospastic or inflammatory airway obstruction. It is still uncertain whether theophylline has a more profound effect on mucociliary clearance than do other agents that are of value in the treatment of asthma, but the evidence suggests that this drug may be more effective than the sympathomimetic bronchodilators. It is unknown whether theophylline affects mucociliary transport throughout the respiratory tract, and whether this effect is also seen in the nose. Studies on ciliary transport have failed to resolve whether the noted improvement in mucous clearance can be attributed mainly to an effect on the cilia or depends, at least in part, on altered mucus viscosity and increased airway patency. However, some of the research suggests that increased ciliary transport can occur without evidence of other significant changes. More careful studies will be required to focus on the response of the cilia in patients with obstructive airway disease. Additional efforts to evaluate the response to theophylline in patients with impaired mucokinesis of the lungs, nose and sinuses can be justified, since the evidence suggests that theophylline's potential value as a major mucokinetic agent has not been adequately recognized.