Disruption of normal mucociliary clearance in the airways is undesirab
le due to the associated risk of increased respiratory disease. Accord
ingly, pharmaceutical formulations delivered via the respiratory tract
should not cause irreversible damage to the mucociliary clearance app
aratus. On the other hand, mucociliary clearance reduces the amount of
time a formulation is in contact with its absorbing membrane with imp
ortant 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 com
ponents of mucociliary clearance are detailed as well as efforts that
have been made to overcome the effect of mucociliary clearance on drug
absorption.