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), although dextromethorphan is a synthetic combination drug not found in the opium poppy itself directly (i.e. a derivative of morphine by chemical dialysis). 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 sigma-1 receptor agonist. DXM and its major metabolite, dextrorphan, also block glutamate receptors at high doses, which produces effets similar to, yet distinict from, the dissociative states created by other dissociative anesthetics such as ketamine, nitrous oxide, and phencyclidine. It was patented in 1949 and approved for medical use in 1953.