Dextromethorphan drug molecule. Molecular model of Dextromethorphan, a cough-suppressant found in many over-the-counter cold and cough medicines. In higher doses than are medically recommended, it will act as a dissociative hallucinogen. It has also been shown that, in combination with quinidine, it can alleviate the emotional lability (laughing or crying uncontrollably) associated with amyotrophic lateral sclerosis and multiple sclerosis. Atoms are colour-coded: carbon (grey), hydrogen (white), nitrogen (purple) and oxygen (red).