Robitussin Cough & Chest Congestion provides symptomatic relief from congested chests and coughs. Robitussin liquid coats and soothes the throat. It contains the expectorant Guaifenesin, which increases the flow of natural secretions along the lower respiratory tract. This liquefying effect helps break up a cough and loosen congestion so you can cough it up and get it off your chest. It also contains the cough suppressant Dextromethorphan which helps quieten the cough for up to 8 hours on a single dose –lets you rest all night without that sleep robbing cough.