Effects of methylxanthines on airway mucociliary function.

Mucociliary interaction and hence mucus clearance in the airways is governed by ciliary activity and the depth and rheologic properties of periciliary fluid and mucus. Therefore, a defect in one or more of these component functions must be responsible for the impairment of mucociliary clearance in patients with a variety of airway diseases. Methylxanthines stimulate ciliary beat frequency, augment net ion secretion with a substantial increase in water flux toward the lumen, and promote mucus secretion in the lower airways. The net result is an enhancement of mucociliary clearance. This beneficial action of methylxanthines on mucociliary function may complement their effects on bronchoconstriction and respiratory muscle dysfunction in patients with chronic bronchitis, cystic fibrosis, and bronchial asthma.