DXM: chemistry

DXM is synthetic and chemically related to codeine [1][2]. It is not itself an opioid [3], though it is reported to belong to the morphinan class of medications [4]. It's the dextro isomer of levomethorphan, a semisynthetic morphine derivative, with molecular formula C18H25NO [5]. DXM does not act as a significant mu-opioid receptor agonist [5][4]. It binds to sigma opioid binding sites [5] and acts as an NMDA receptor antagonist, an action thought to underlie its efficacy in treating cough [3].

Supratherapeutic doses of DXM mimic the activity of dissociative hallucinogens such as phencyclidine and ketamine [3], producing PCP-like behavioral effects [5]. DXM and its metabolite dextrorphan act as NMDA receptor antagonists [5].

Approximately 5-10% of people are poor DXM metabolizers, which increases their risk for overdose and death [5].

References

1. DXM (Dextromethorphan) — National Drug Intelligence Center (NDIC), U.S. Department of Justice
2. Dextromethorphan | Cough Suppressant, Antitussive, DM — Encyclopædia Britannica
3. Classics in Chemical Neuroscience: Dextromethorphan (DXM) — PubMed
4. Dextromethorphan — Wikipedia
5. DEXTROMETHORPHAN — Drug Enforcement Administration (DEA) Diversion Control Division