A peripheral mechanism of antitussive activity may
be postulated by invoking the presumed effect of
guaifenesin on airway mucus. The “hydration hypothesis”
proposes that guaifenesin, by increasing
the effective hydration of the respiratory tract, maintains
the sol layer needed for ciliary clearance and
reduces the viscosity of respiratory mucus, thereby
further facilitating its removal by natural clearance
processes.2 Perhaps the findings of the present study
may be explained by increased mucus volume, or
otherwise altered airway mucus, serving as a more
effective barrier shielding cough receptors within the
respiratory epithelium from the tussive stimulus.