Hydrocodone suppresses the cough reflex by depressing the medullary cough center. The precise mechanism of action of hydrocodone and other opiates is not known, although it is believed to relate to the existence of opiate receptors in the central nervous system. Pseudoephedrine hydrochloride is an orally effective nasal decongestant that acts on alpha-adrenergic receptors in the mucosa of the respiratory tract producing vasoconstriction. Pseudoephedrine shrinks swollen nasal mucous membranes, reduces tissue hyperemia, edema and nasal congestion and increases nasal airway patency. Drainage of sinus secretions is increased and obstructed Eustachian ostia may be opened.
Pseudoephedrine produces little if any rebound congestion.
Guaifenesin is an expectorant which enhances the flow of respiratory tract secretions. The enhanced flow of less viscid secretions lubricates irritated respiratory tract membranes, promotes cilliary action and facilitates the removal of inspissated mucus. As a result, sinus and bronchial drainage is improved and nonproductive coughs become more productive and less frequent.