>>9496168Dextromethorphan (also known as robo, dex, DM, and DXM) is a dissociative substance of the morphinan class. DXM is the primary active ingredients in many common over-the-counter (OTC) cold and cough medicines. When exceeding approved doses, DXM produces dissociative effects similar to those of ketamine and phencyclidine (PCP). The pharmacology of DXM is not completely understood, but it is thought to act primarily by blocking NMDA receptors in the brain.