Robitussin DM is dextromethorphan and guaifenesin. Destromethorphan surpresses a cough. Guaifenesin loosens congestion in the chest making it easier to cough and come out. This medication is used to treat cough and congestion caused by colds, allergies, or infections.
Robitussin DM helps by affecting the signals in the brain that triggers the cough reflex. This medications does not treat coughs resulting from asthma, smoking or emphysema. This medication is a very safe medication to use, if it is used correctly.