For frequent, persistent coughs, Robitussin Cough & Chest Congestion DM thins mucus to relieve chest congestion and gets your cough under control. Robitussin acts to suppress coughs and thin mucus so your cough is more productive, all with a non-drowsy formula that works even at the height of your cold. Provides soothing action, it suppresses cough plus it helps loosen phlegm and thins bronchial secretions to make cough more productive.