Mucocilliary clearance and drug delivery via the respiratory tract

Disruption of normal mucociliary clearance in the airways is undesirable due to the associated risk of increased respiratory disease. Accordingly, pharmaceutical formulations delivered via the respiratory tract should not cause irreversible damage to the mucociliary clearance apparatus. On the other hand, mucociliary clearance reduces the amount of time a formulation is in contact with its absorbing membrane with important consequences for the bioavailability of the delivered drug. In this review the components of the mucociliary apparatus are described and methods of measuring ciliary beat frequency, mucociliary transport and mucociliary clearance are reviewed. Substances known to alter components of mucociliary clearance are detailed as well as efforts that have been made to overcome the effect of mucociliary clearance on drug absorption.