Mucinex DM controls cough relieves chest congestion 4 hour dosing. Mucinex pantented bi-layer tablet contains an immediate-release layer on one side and extended-release layer on the other side which allows extended relief for up to 12 hours. Mucinex DM powerful symptom relief: Mucinex DM 12 hour controls cough, relieves chest congestion and thins & loosens mucus.