Dextromethorphan  (DXM or DM)  is a medication most often used as a cough suppressant in over-the-counter cold and cough medicines.  It is sold in syrup,  tablet,  spray,  and lozenge forms.

It is in the morphinan class of medications with sedative,  dissociative,  and stimulant properties  (at lower doses).  In its pure form, dextromethorphan occurs as a white powder.

DXM is also used recreationally.  When exceeding approved dosages,  dextromethorphan acts as a dissociative hallucinogen.  It has multiple mechanisms of action,  including actions as a nonselective serotonin reuptake inhibitor and a sigma-1 receptor agonist.  DXM and its major metabolite,  dextrorphan,  also act as an NMDA receptor antagonist at high doses,  which produces effects similar to,  yet distinct from,  the dissociative states created by other dissociative anesthetics such as ketamine,  nitrous oxide,  and phencyclidine.