What is the mechanism of action for expectorants?

Expectorants work by decreasing the thickness of mucus in the airways, which makes it easier for patients to cough up phlegm and clear their respiratory passages. This action helps to alleviate congestion and promote a productive cough rather than a dry cough. By thinining the mucus, expectorants enhance mucociliary clearance, allowing for better respiratory function and providing relief from conditions like bronchitis and other respiratory infections.

The other options do not effectively describe the role of expectorants. Increasing mucus thickness would lead to more congestion and discomfort, while suppression of coughing is associated with antitussives, which serve a different purpose. Constriction of blood vessels pertains to a different category of medications, usually related to vasoconstrictors, and does not pertain to the function of expectorants at all.