Dextromethorphan (DXM or DM) is a drug. It is used to prevent coughs in many over-the-counter cold and cough medicines. Dextromethorphan can also be used for pain relief or for psychological conditions. It is sold in syrup, tablet, and lozenge forms, manufactured under several different brand names and generic labels. In its pure form, dextromethorphan is a white powder.