Dextromethorphan (DXM)
Antitussive found in OTC cough syrups. At therapeutic doses acts as a sigma-1 agonist and weak serotonin reuptake inhibitor. At high recreational doses (>300 mg) becomes a potent NMDA antagonist via its metabolite dextrorphan, producing dissociative effects across four dose-dependent "plateaus." Exhibits highly polymorphic CYP2D6-dependent metabolism: extensive metabolizers have ~4h half-life, poor metabolizers ~20-30h. Serotonergic at all doses, dangerous with SSRIs/MAOIs.
Projected serum levels — 30 mg, as needed (shown daily)
Maintenance schedule: 30 mg as needed (shown daily) (oral).
Modeled steady state after ~1 days: peak ≈ 2.9 mg, trough ≈ 0.024 mg body load. Population-based estimate over 15 days for a 30 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.
Key facts
- Category
- Dissociative
- Route modeled
- Oral
- Model confidence
- inferred
- Half-life
- 3 h
- Common dose
- 30 mg
- Reference dose range
- 15–60 mg (single dose)
- Suggested cadence
- as needed (shown daily)
- Validated against
- 30 mg oral — Cmax 0.003 mg/L at 2 h
Documented interactions
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danger
1P-LSD (1-Propionyl-LSD) + Dextromethorphan (DXM)
1P-LSD (1-Propionyl-LSD) and Dextromethorphan (DXM) both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).
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danger
25I-NBOMe + Dextromethorphan (DXM)
25I-NBOMe and Dextromethorphan (DXM) both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).
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danger
2C-I (2,5-Dimethoxy-4-iodophenethylamine) + Dextromethorphan (DXM)
2C-I (2,5-Dimethoxy-4-iodophenethylamine) and Dextromethorphan (DXM) both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).
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danger
2C-B (4-Bromo-2,5-dimethoxyphenethylamine) + Dextromethorphan (DXM)
2C-B (4-Bromo-2,5-dimethoxyphenethylamine) and Dextromethorphan (DXM) both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental…
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danger
3-MeO-PCP (3-Methoxyphencyclidine) + Dextromethorphan (DXM)
3-MeO-PCP (3-Methoxyphencyclidine) and Dextromethorphan (DXM) both push the SERT, nmda, and sigma 1 in the same direction.
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danger
4-AcO-DMT (Psilacetin) + Dextromethorphan (DXM)
4-AcO-DMT (Psilacetin) and Dextromethorphan (DXM) both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).
Serum checks 159 modeled interaction pairings for dextromethorphan (dxm) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.
Research behind this entry
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Pharmacokinetics of dextromethorphan and metabolites in humans: influence of the CYP2D6 phenotype and quinidine inhibition
Characterized DXM and dextrorphan pharmacokinetics across CYP2D6 phenotypes, showing extensive metabolizer half-life of ~2-4h vs poor metabolizer half-life of ~20h, with quinidine converting extensive to poor…
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Pharmacokinetics and pharmacodynamics of dextromethorphan: clinical and forensic aspects
Comprehensive review of DXM clinical pharmacology including dose-dependent NMDA antagonism, serotonergic activity, CYP2D6 polymorphism effects on PK, and forensic detection windows.
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Physiologically based pharmacokinetic (PBPK) modeling of the role of CYP2D6 polymorphism for metabolic phenotyping with dextromethorphan
PBPK model predicting DXM/dextrorphan metabolic ratios across CYP2D6 genotypes, validating half-life estimates of 1.4h (EM) to 29.5h (PM) and drug interaction predictions.
3 published studies referenced in the app, each with a plain-language summary.