DXM: dosage

The typical antitussive adult dose of DXM is 15 or 30 mg taken three to four times daily [1]. At that dose, the anti-cough effect lasts five to six hours [1], and side effects are rarely reported [1]. Recreational use means deliberately taking more than this to bring on heightened awareness, altered time perception, and visual hallucinations [2]. There is no reliable figure here for where that heightened-effect range begins or ends, or for what separates it from an overdose — nothing in this reference gives a recreational threshold, so treat any dose above the antitussive range as unmapped territory.

Most people using DXM this way take it orally; some snort the pure powdered form [3]. DXM powder sold over the internet carries a risk that's separate from the dose you intend to take: its composition and dose can't be verified with certainty [1]. If you're using a multi-ingredient cough or cold product instead, the other active ingredients carry their own risks, unrelated to DXM's effects and not always immediately obvious — pseudoephedrine can raise blood pressure, and acetaminophen can cause delayed liver damage [1].

Around 5 to 10% of people are poor metabolizers of DXM. This raises their risk of overdose and death [1].

DXM should not be taken with antidepressants, because of the risk of serotonergic syndrome [1]. High doses combined with alcohol or other central nervous system depressants are particularly dangerous — deaths have been reported from this combination [1].

References

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