Dextromethorphan is a 6-methoxy-11-methyl-1,3,4,9,10,10a-hexahydro-2H-10,4a-(epiminoethano)phenanthrene in which the sterocenters at positions 4a, 10 and 10a have S-configuration. It is a prodrug of dextrorphan and used as an antitussive drug for suppressing cough. It has a role as a NMDA receptor antagonist, a neurotoxin, a xenobiotic, an environmental contaminant, an antitussive, a prodrug and a oneirogen. It is functionally related to a dextrorphan. It is an enantiomer of a levomethorphan.