DXM: interactions

Alcohol and other CNS depressants. High-dose DXM combined with alcohol or other central nervous system depressants is particularly dangerous — deaths have been reported from this combination [1].

Antidepressants and other serotonergic drugs. DXM should not be taken with antidepressants because of the risk of a life-threatening serotonin syndrome [1]. DXM is reported to have agonist effects at serotonin receptors, and serotonin syndrome has also been described as arising from interactions between DXM and other serotonergic drugs [2].

Cardiac and adrenergic load. DXM is reported to produce dose-related adrenergic effects — high blood pressure and sweating — described as resulting from inhibition of catecholamine reuptake [2]. Combination cold products containing pseudoephedrine carry their own risk of increased blood pressure [1].

Combination products. DXM is found alone and in many over-the-counter combination products alongside other active ingredients [1][3], and abuse of these products causes harm from those ingredients directly: raised blood pressure from pseudoephedrine and potential delayed liver damage from acetaminophen [1]. Acetaminophen levels should be obtained when DXM toxicity with possible concomitant ingestion is suspected [2].

Metabolism varies. Roughly 5–10% of people are poor metabolizers of DXM, and this raises their risk of overdose and death [1].

References

1. DEXTROMETHORPHAN — Drug Enforcement Administration (DEA) Diversion Control Division
2. Dextromethorphan abuse — Canadian Medical Association Journal (CMAJ)
3. DXM (Dextromethorphan) — National Drug Intelligence Center (NDIC), U.S. Department of Justice