Each 20 mL dose contains 20 milligrams of dextromethorphan HBr and 200 milligrams of guaifenesin USP Dextromethorphan suppresses coughs while guaifenesin breaks up the phlegm that causes coughing With Robitussin Cough + Chest Congestion, coughs are controlled, chest congestion is relieved and mucus is thinned and loosened Bottle contains 4 ounces of raspberry flavor, nondrowsy cough medicine.