Psychedex is in open beta. We are still fine-tuning the generation and review process. Please double-check sources.
ketamine, PCP, nitrous oxide +1 moreketamine, PCP, nitrous oxide, memantine show less
Dextromethorphan
(+)-3-methoxy-17-methylmorphinan
DXM (dextromethorphan) is a synthetic dissociative of the morphinan class. It is the non-opioid mirror image of levomethorphan, retaining cough-suppressing activity without meaningful opioid effects.[1] It blocks glutamate signaling in the brain[2] and inhibits serotonin reuptake,[3] producing its characteristic dissociation and euphoria.
DXM (dextromethorphan) is a synthetic dissociative of the morphinan class. It is the mirror-image enantiomer of the opioid levomethorphan, retaining cough-suppressing activity without meaningful opioid effects.[1] DXM is an NMDA receptor antagonist and sigma-1 receptor agonist,[2] producing its effects by blocking glutamate-driven signaling in cortical and thalamic circuits while also inhibiting serotonin reuptake.[3]
Psychedex is in open beta. We are still fine-tuning the generation and review process. Please double-check sources.
ketamine, PCP, nitrous oxide +1 moreketamine, PCP, nitrous oxide, memantine show less
DXM was first tested as a cough suppressant in 1954 and FDA-approved in 1958 as the first non-opioid antitussive.[1] Recreational misuse was documented by the 1960s, and a surge in teenage abuse prompted over 20 US states to restrict sales to adults.[4] It is now also an ingredient in two FDA-approved psychiatric medications — one for a neurological condition that causes uncontrollable emotional outbursts,[5] and one for depression.[6]
Subjective effects include dissociation, euphoria, time alteration, derealization, and vivid hallucinations at higher amounts. The experience escalates through dose-dependent stages — from mild stimulation to a profound mind-body separation — with a warmer, more euphoric character than ketamine. Nausea, dizziness, confusion, and motor impairment are common unwanted effects.
Both physical and psychological dependence develop with chronic use,[7][4] and no human lethal dose has been established. The primary acute danger is combining DXM with serotonergic drugs — MAOIs in particular can trigger a life-threatening overheating and seizure response;[8] genetic variation in liver metabolism means identical doses affect people very differently.[9] Decades of clinical use and multiple FDA approvals provide a strong evidence base, but no controlled studies of recreational-dose effects have been published.
History[edit]
Discovery
The morphinan chemical family was explored at Hoffmann-La Roche in the mid-1940s, with a US patent granted in 1950.[10] The two mirror-image forms of methorphan had completely different effects: the levorotatory form was a potent opioid; the dextrorotatory form suppressed coughs without opioid activity. DXM was tested as an antitussive in 1954 — partly funded by the US Navy and CIA — and FDA-approved in 1958 as the first non-narcotic cough suppressant.[1]
Clinical adoption and misuse
DXM rapidly displaced codeine as the dominant over-the-counter cough suppressant worldwide.[1] Recreational misuse appeared in medical literature by the 1960s and escalated sharply among teenagers by the 2000s.[4] Over 20 US states have since passed laws restricting DXM sales to individuals 18 or older.[11]
Therapeutic renaissance
DXM's multiple receptor targets — initially a pharmacological inconvenience — became therapeutically useful once its pharmacology was understood. The FDA approved Nuedexta in 2010 for pseudobulbar affect, a neurological condition causing uncontrollable laughing or crying.[5] In 2022, Auvelity was approved for major depression in adults.[6]
The name dextromethorphan combines Latin dexter (right) — referring to the molecule's dextrorotatory optical rotation — with methorphan, the morphinan-class parent compound. The abbreviation DXM is universal in both clinical and recreational contexts. In recreational culture, DXM's dose-dependent effects are traditionally organized into four plateaus, a framework originating in online user communities in the late 1990s that maps escalating dissociative intensity from mild stimulation to complete hallucinogenic dissociation.
Chemistry[edit]
Structural class
DXM belongs to the morphinan chemical class — the same family as codeine and morphine, though DXM has no meaningful opioid activity. Its molecular formula is C₁₈H₂₅NO.
The liver enzyme CYP2D6 converts DXM into an active metabolite called dextrorphan, which binds the same brain receptors with roughly eightfold greater potency and is largely responsible for the dissociative effects at higher doses.[12]
Pharmacology[edit]
Mechanism of action
DXM blocks glutamate signaling in the brain by occupying a channel inside NMDA receptors — the same channel targeted by ketamine and PCP.[2] Its liver metabolite dextrorphan does this with roughly eightfold greater potency,[2] and dextrorphan accumulation at higher doses drives the characteristic disconnection from reality.[7]
DXM also activates sigma-1 receptors,[2] which are involved in emotional regulation and likely contribute to its antidepressant effects. It inhibits serotonin reuptake,[3] which adds a warm, euphoric quality to the experience — and is the reason combining DXM with serotonergic drugs is dangerous.
Pharmacokinetics
The liver enzyme CYP2D6 converts DXM to dextrorphan.[12] In the roughly 90% of people who metabolize DXM quickly, blood levels stay low and the drug clears fast; in the roughly 8–10% who metabolize it slowly, the same dose produces far higher blood levels and lasts far longer.[9] Drugs that block CYP2D6 produce the same effect pharmacologically — bupropion raises DXM exposure more than 100-fold,[13] and quinidine extends DXM's half-life from 2–3 hours to over 16 hours.[9]
Neuroscience[edit]
Where it acts
DXM's dissociative effects arise from blocking NMDA receptors in the cortex and thalamus.[2] These receptors maintain the coherent neural activity that underlies waking consciousness; blocking them disrupts the brain's sense of self and spatial reality, producing depersonalization and derealization. The blockade is use-dependent — circuits that are more active get disrupted more.[14]
Why it matters
DXM also activates sigma-1 receptors[2] in brain areas involved in emotion and memory. This increases levels of BDNF — a protein that promotes neuron growth and survival[15] — which is believed to drive the rapid antidepressant effects seen with NMDA antagonists like ketamine. The FDA approval of DXM/bupropion for depression[16] validates this mechanism clinically.
Poor metabolizers accumulate mostly parent DXM (sigma-1 and serotonin-dominant) while extensive metabolizers produce mostly dextrorphan (NMDA-dominant) — these populations may experience qualitatively different states from identical doses, but no controlled comparison exists.
Subjective Effects[edit]
DXM's character is shaped by two unusual variables: how much was taken, and how the individual's liver processes it. Genetic variation in a liver enzyme means two people taking the same dose may experience qualitatively different states. The experience escalates through distinct stages as dose increases, from mild stimulation to complete disconnection from the self.
Compared to ketamine, DXM's dissociation arrives more slowly and lasts much longer. Where ketamine can feel cold and anesthetic at dissociative depths, DXM tends toward warmth and euphoria — reflecting its additional activity on serotonin pathways layered onto the core glutamate blockade.
First tested as a cough suppressant in 1954 and FDA-approved in 1958 as the first non-narcotic alternative to codeine,[1] DXM's complex receptor profile later proved therapeutically valuable — FDA approval of dextromethorphan/quinidine for pseudobulbar affect in 2010[4] and dextromethorphan/bupropion for major depressive disorder in 2022[5] established it as a validated psychiatric agent. Recreational misuse, predominantly among adolescents, has prompted age-restriction legislation in over 20 US states.
Subjective effects include dissociation, euphoria, time alteration, derealization, and hallucinosis. The experience unfolds through dose-dependent stages — from mild stimulation at low doses to profound disconnection between mind and body at high doses — with a warmer, more euphoric character than ketamine at comparable dissociative depths, reflecting DXM's serotonergic and sigma-1 receptor activity. Nausea, dizziness, confusion, and motor impairment are common unsought effects.
Physical and psychological dependence develop with chronic use,[6][7] and no human lethal dose has been established. The principal acute danger is serotonin syndrome when combined with serotonergic medications — MAOIs are an absolute contraindication[8] — while CYP2D6 genetic variation means identical doses produce vastly different plasma levels across individuals.[9] Decades of clinical use and multiple FDA-approved formulations provide a strong pharmacological evidence base, though no controlled studies of recreational-dose effects have been published.
History[edit]
Discovery
The morphinan scaffold from which DXM derives was explored at Hoffmann-La Roche laboratories in the mid-1940s, with a US patent granted in 1950.[10] Resolution of the two enantiomers revealed that the levorotatory form (levomethorphan) was a potent opioid analgesic while the dextrorotatory form (dextromethorphan) retained cough-suppressing efficacy without meaningful opioid effects. In 1954, DXM was successfully tested as an antitussive in research partially funded by the US Navy and the CIA, part of a broader program to identify non-addictive codeine replacements.[1]
Clinical adoption and misuse
The FDA approved DXM in 1958 as the first non-opioid, non-narcotic cough suppressant available without prescription,[1] and it rapidly displaced codeine as the dominant OTC antitussive worldwide.[1] Recreational misuse was documented in medical literature by the 1960s, and by the 2000s an alarming increase in abuse cases was noted among teenagers.[7] Over 20 US states subsequently enacted minimum purchase age laws restricting DXM sales to individuals 18 or older.[11]
Therapeutic renaissance
DXM's multi-receptor profile — initially an inconvenience for a cough suppressant — became therapeutically valuable as its pharmacology was characterized in detail. In 2010, the FDA approved Nuedexta (dextromethorphan/quinidine) as the first treatment for pseudobulbar affect,[4] and in 2022 Auvelity (dextromethorphan/bupropion) received approval for major depressive disorder in adults.[5] Both formulations exploit CYP2D6 inhibition to raise DXM bioavailability.[9][12]
The name dextromethorphan combines Latin dexter (right) — referring to the molecule's dextrorotatory optical rotation — with methorphan, the morphinan-class parent compound. The abbreviation DXM is universal in both clinical and recreational contexts. In recreational culture, DXM's dose-dependent effects are traditionally organized into four plateaus, a framework originating in online user communities in the late 1990s that maps escalating dissociative intensity from mild stimulation to complete hallucinogenic dissociation.
Chemistry[edit]
Structural class
DXM belongs to the morphinan chemical class, sharing the tetracyclic morphinan scaffold with opioids such as morphine, codeine, and levorphanol. The skeleton consists of a phenanthrene core fused to a piperidine ring. DXM is distinguished from classical opioids by its dextrorotatory stereochemistry and by a methoxy group replacing the 3-hydroxyl group, which abolishes meaningful μ-opioid binding.
Molecular properties
| Molecular formula | C₁₈H₂₅NO |
| Molecular weight | 271.4 g/mol |
The methoxy group at position 3 is a key pharmacophoric feature: its removal by a liver enzyme (CYP2D6) yields the active metabolite dextrorphan, which carries substantially greater NMDA affinity.[13] DXM is marketed predominantly as the hydrobromide salt for improved water solubility. Dose values in this article refer to the hydrobromide salt unless otherwise specified.
Stereochemistry
DXM is the (+)-enantiomer of methorphan. Its mirror image, levomethorphan, is a potent mu-opioid agonist and a controlled substance.[1] This enantiomeric pair is a striking case of stereospecific pharmacology: identical atomic composition, but the spatial arrangement of atoms determines whether the molecule engages opioid receptors (levorotatory) or NMDA and sigma receptors (dextrorotatory).
Physical properties
DXM free base is a white crystalline powder with a melting point of 106–108 °C.[14] The compound is lipophilic (LogP 3.6–4.1),[14][15] consistent with rapid penetration into the central nervous system.
Pharmacology[edit]
Mechanism of action
DXM produces its effects through an unusually broad receptor profile. The primary dissociative mechanism is uncompetitive NMDA receptor antagonism — DXM blocks the ion channel pore at the same site targeted by PCP and ketamine.[2] Its metabolite dextrorphan binds the same site with roughly eightfold greater potency,[2] and dextrorphan accumulation at supratherapeutic doses drives the characteristic dissociative effects.[6]
DXM is also a potent sigma-1 receptor agonist,[2] engaging limbic circuits involved in emotional regulation. This target is considered the most probable mechanism behind DXM's efficacy in pseudobulbar affect[16] and a likely contributor to its antidepressant activity.[3]
A third major action is serotonin transporter inhibition,[3] which contributes to antidepressant-like effects[17] and, critically, the risk of serotonin syndrome when DXM is combined with other serotonergic drugs. Additional targets include nicotinic acetylcholine receptor antagonism[18][8] and voltage-gated calcium channel blockade.[19]
DXM has minimal μ-opioid activity at therapeutic or typical recreational doses.[8] Weak interactions have been reported at high concentrations,[17] but DXM was developed specifically as a non-narcotic antitussive and should not be classified as an opioid.
Pharmacokinetics
DXM undergoes extensive first-pass metabolism in the liver, primarily via CYP2D6.[13] The major pathway converts DXM to dextrorphan, the active metabolite with greater NMDA affinity. A secondary pathway produces 3-methoxymorphinan. Both metabolites are processed further before renal excretion; less than 1% of parent DXM appears unchanged in urine.
CYP2D6 genetic variation is the single most important factor shaping DXM's effects. In the roughly 90% of people who are extensive metabolizers, oral bioavailability is only 1–2% with a half-life of 2–3 hours.[9][20] In poor metabolizers (~8–10% of Caucasians), bioavailability rises to 60–80% and the half-life extends to 15–20 hours.[9]
CYP2D6 inhibitors produce the same effect pharmacologically: quinidine extends DXM's half-life from 2–3 hours to over 16 hours,[9] and bupropion raises DXM exposure more than 100-fold.[21] This means identical doses can produce vastly different experiences — and vastly different risk levels — depending on genetics or concurrent medications.
Neuroscience[edit]
Where it acts
DXM's dissociative effects arise from NMDA blockade disrupting communication between the cortex and deeper brain structures. NMDA receptors on cortical and thalamic neurons maintain the coherent activity underlying waking consciousness; blocking them produces the dose-dependent disconnection — depersonalization, derealization, mind-body separation — that defines dissociative states.
At higher doses, dextrorphan accumulation at the NMDA channel[2] disrupts thalamic gating more profoundly, progressing from selective disruption of self-referential processing to global impairment of awareness. The blockade is use-dependent, meaning highly active neural circuits experience disproportionate antagonism.[22]
Why it matters
DXM's sigma-1 receptor activity[2] engages limbic regions — hippocampus, amygdala, prefrontal cortex — implicated in emotional regulation and neuroplasticity. Clinical evidence shows DXM increases BDNF (a key growth factor for neurons) in bipolar disorder patients,[23] and preclinical models demonstrate neuroprotective effects against traumatic brain injury.[24]
The FDA approval of dextromethorphan/bupropion for depression[25] validates the hypothesis that NMDA antagonism triggers rapid antidepressant effects through a cascade distinct from traditional antidepressants — the same pathway attributed to ketamine, though DXM's sigma-1 agonism adds a mechanistic dimension absent from the ketamine model.
What is the relative contribution of parent DXM versus dextrorphan to the dissociative experience? Poor metabolizers accumulate mostly parent DXM (sigma-1/serotonin-dominant) while extensive metabolizers produce mostly dextrorphan (NMDA-dominant) — these populations may experience qualitatively different states from identical doses, but no controlled comparison exists.
Subjective Effects[edit]
DXM's subjective character is shaped by an unusual pharmacological variable: CYP2D6 metabolizer status determines whether the dominant psychoactive species is dextrorphan (NMDA-driven dissociation) or parent DXM (sigma-1 receptor and serotonin-driven). Two people taking the same dose may experience qualitatively different states — a degree of pharmacogenomic variability unmatched by other dissociatives. Effects emerge in dose-dependent stages traditionally described as four plateaus, progressing from mild stimulation and euphoria through increasingly profound dissociation to full hallucinosis. Set and setting influence emotional tone, but metabolizer phenotype is the primary modulator.
Compared to ketamine, DXM's dissociation develops more gradually, lasts substantially longer, and carries a serotonergic warmth that ketamine lacks. The experience is often described as more euphoric and emotionally textured at comparable dissociative depths, likely reflecting sigma-1 agonism and serotonin reuptake inhibitor layered onto the core NMDA blockade.
Effect Grid
At common doses (200–400 mg oral DXM HBr), the dissociative character of the experience becomes unmistakable. Euphoria intensifies, often accompanied by a sense of bodily dissociation — the feeling of separation between mind and physical form. Music distortion and enhancement become prominent. Visual distortions emerge: drifting of surfaces, closed-eye visuals with geometric or abstract imagery, and altered color perception. Time distortion is marked, with subjective time typically feeling stretched. Thought disorganization increases, with dream-like or surreal cognitive patterns.
Physically, pronounced nystagmus, ataxia, and motor incoordination are typical. Nausea and vomiting occur in a significant minority. Tachycardia and mild hypertension are common. Speech becomes slurred. Sleep is impossible for 6–8 hours. Functional impairment is substantial — driving or operating machinery is unsafe.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Perspective distortion · Tracers · Visual haze / noise · Visual drifting · Auditory distortion · Music enhancement · Proprioceptive distortion · After-images · Visual morphing · Touch suppression · Auditory enhancement · Color enhancement · Auditory misinterpretation · Brightness alteration · Holotropic state · Sensory deprivation · Sleep-transition hallucinations · Visual magnification · Dreaming enhancement · Synesthesia · Color alteration · Geometry · Peripheral vision distortion · Sound sensitivity · Visual breathing · Auditory suppression · Environmental patterning · Light sensitivity · Tinnitus · Touch enhancement · Visual diffraction · Visual melting · Visual processing acceleration · Visual processing suppression · Internal hallucinations · Auditory hallucinations · Environmental orbism / cubism · Visual scenery slicing · External hallucinations · Object transformations · Visual recursion · Gustatory hallucination
Auditory distortion · Music enhancement · Proprioceptive distortion · After-images · Visual morphing · Touch suppression · Auditory enhancement · Color enhancement · Auditory misinterpretation · Brightness alteration · Holotropic state · Sensory deprivation · Sleep-transition hallucinations · Visual magnification · Dreaming enhancement · Synesthesia · Color alteration · Geometry · Peripheral vision distortion · Sound sensitivity · Visual breathing · Auditory suppression · Environmental patterning · Light sensitivity · Tinnitus · Touch enhancement · Visual diffraction · Visual melting · Visual processing acceleration · Visual processing suppression · Internal hallucinations · Auditory hallucinations · Environmental orbism / cubism · Visual scenery slicing · External hallucinations · Object transformations · Visual recursion · Gustatory hallucination
Body high · Body schema distortion · Nausea · Pain suppression · Pupil dilation · Stimulation · Bodily lightness · Spontaneous body sensations · Involuntary body movements · Muscle relaxation · Appetite suppression · Bodily heaviness · Laughter fits · Physical fatigue · Tingling / electric sensations · Vibrations / buzzing · Sexual arousal suppression · Excessive sweating · Dry mouth · Heart rate perception changes · Insomnia · Tactile euphoria · Vomiting · Sexual arousal enhancement · Abnormal heartbeat · Respiratory depression · Restlessness · Trembling · Wakefulness · Increased urination · Bodily dissociation · Tactile hallucination
Pain suppression · Pupil dilation · Stimulation · Bodily lightness · Spontaneous body sensations · Involuntary body movements · Muscle relaxation · Appetite suppression · Bodily heaviness · Laughter fits · Physical fatigue · Tingling / electric sensations · Vibrations / buzzing · Sexual arousal suppression · Excessive sweating · Dry mouth · Heart rate perception changes · Insomnia · Tactile euphoria · Vomiting · Sexual arousal enhancement · Respiratory depression · Restlessness · Trembling · Wakefulness · Increased urination · Bodily dissociation · Tactile hallucination
Memory suppression · Focus suppression · Information processing suppression · Thought disorganization · Cognitive fatigue · Immersion enhancement · Motivation suppression · Cognitive euphoria · Thought deceleration · Pattern recognition suppression · Humor enhancement · Novelty enhancement · Aesthetic enhancement · Introspection enhancement · Memory fragmentation · Conceptual thinking · Compulsive redosing urge · Language suppression · Openness enhancement · Thought connectivity · Thought loops · Creativity enhancement · Cognitive dysphoria · Delusions of sobriety · Amnesia · Delusions · Delirium
Thought disorganization · Cognitive fatigue · Immersion enhancement · Motivation suppression · Cognitive euphoria · Thought deceleration · Pattern recognition suppression · Humor enhancement · Novelty enhancement · Aesthetic enhancement · Introspection enhancement · Memory fragmentation · Conceptual thinking · Language suppression · Openness enhancement · Thought connectivity · Thought loops · Creativity enhancement · Cognitive dysphoria · Delusions of sobriety · Amnesia · Delusions · Delirium
Anxiety · Emotional lability · Emotional suppression · Dysphoria · Simultaneous emotions
Simultaneous emotions
Communication suppression · Sociability suppression · Social disconnection · Automaticity · Emotional susceptibility · Ego inflation · Craving · Flow state · Sociability enhancement · Cognitive disconnection · Boundary dissolution · Ego dissolution · Identity alteration
Emotional susceptibility · Ego inflation · Craving · Flow state · Sociability enhancement · Cognitive disconnection · Boundary dissolution · Ego dissolution · Identity alteration
Near-death experience · Non-dual awareness · Voidness · Cessation
Timeline
First alerts emerge as mild warmth, slight mood shift, or faint nausea. The wide onset window (30–120 minutes) reflects CYP2D6-dependent absorption and first-pass metabolism variability.
Effects build steadily: mood elevation, growing body dissociation, and emerging perceptual shifts. Nausea peaks during this phase for many users. A sense of physical heaviness or floating develops.
Maximum dissociative intensity. Euphoria, depersonalization, perceptual distortions, and thought disorganization reach their zenith. Music distortion and enhancement are most pronounced.
Dissociative effects sustain at reduced intensity. Cognitive cloudiness and motor impairment persist. The dreamy, floating quality of the experience stabilizes.
Gradual return of normal body awareness and environmental connection. Cognitive fog lifts slowly. Mild residual euphoria or emotional flatness.
Residual cognitive cloudiness, mild mood changes, and subtle dissociative aftereffects may persist for 4–24 hours. Duration is strongly CYP2D6-dependent — poor metabolizers experience substantially longer aftereffects.
⚠ Do not drive or operate machinery until at least 24 hours after ingestion, or longer if residual impairment is felt.
Safety[edit]
- Acute toxicity
- Moderate
- Chronic toxicity
- Moderate
- Withdrawal
- Mild
- Tolerance buildup
- moderate
- Tolerance reset
- 10 days
- Physical
- Low
- Psychological
- Moderate
- Compulsive redosing
- Low
- Dose escalation
- Moderate
- Cross-tol.
- ketamine · PCP · nitrous oxide
Toxicity
No human lethal dose has been established for DXM. The margin between a therapeutic antitussive dose (15–30 mg) and serious toxicity is relatively wide, though it narrows substantially with concurrent medications or poor metabolizer status.
Toxicity thresholds
Evidence-based guidelines establish the following clinical thresholds for DXM ingestion[17]:
- Above 4 mg/kg: Up to 64% of people experience psychoactive effects
- 5–7.5 mg/kg: Increased monitoring recommended
- Above 7.5 mg/kg: Emergency department referral recommended
Common effects at doses above 4 mg/kg include euphoria, nausea and vomiting, involuntary eye movement, and dizziness.[8]
Severe overdose
At high doses, DXM toxicity combines dissociative, serotonergic, and sedative features.[8] Serotonin syndrome — a life-threatening overheating and seizure response — is the most dangerous acute risk, especially when combined with serotonergic medications. Other severe outcomes include respiratory depression (especially with sedative combinations), dangerous overheating, and muscle breakdown from prolonged seizures.
Published cases document survival from massive ingestions — including 5,600 mg causing prolonged seizures with full recovery by day 9,[18] and over 100 tablets causing shock and convulsions requiring intensive care[19] — though these required aggressive hospital intervention.
CYP2D6 and toxicity
Poor metabolizers and people taking CYP2D6-inhibiting medications (paroxetine, fluoxetine, bupropion, quinidine) accumulate far higher DXM blood levels from the same dose. A dose tolerated by most people may produce life-threatening toxicity in a poor metabolizer.
Psychological risks
High doses can produce paranoia, hallucinations, severe agitation, and disorientation.[8] Chronic misuse is associated with sustained psychosis, depression, and cognitive impairment.[7] The risk is amplified in people with pre-existing psychiatric conditions, particularly psychotic spectrum disorders.
Tolerance & dependence
Tolerance develops with repeated use. Cross-tolerance occurs with other NMDA antagonist dissociatives — ketamine and PCP. Community-reported timelines — buildup with prolonged use, roughly 5-day half-life, approximately 1.5-week full reset — have not been validated in controlled studies.citation needed
Physical and psychological dependence with chronic DXM use is documented, with withdrawal syndromes consistent with NMDA antagonist discontinuation.[7][4] In animal models, DXM also modulates opioid and nicotine dependence behaviors.[20]
Drug Interactions
DXM's multiple receptor targets create interaction risks through both additive drug effects and altered metabolism.
Serotonergic interactions
MAOIs are an absolute contraindication — combining them with DXM causes catastrophic serotonin accumulation with documented fatalities, requiring a minimum 14-day washout.[8][17] SSRIs and SNRIs carry significant serotonin syndrome risk, compounded when the SSRI also inhibits CYP2D6 — paroxetine and fluoxetine create both pharmacological and metabolic amplification.[7][21] Tramadol and MDMA also pose serious serotonin syndrome risk.
CNS depressant interactions
Alcohol, GHB/GBL, benzodiazepines, and opioids produce additive sedation and respiratory depression with DXM. Dissociative impairment of protective reflexes also increases aspiration risk during sedation.
Pharmacokinetic interactions
Strong CYP2D6 inhibitors dramatically increase DXM blood levels. Bupropion raises DXM exposure more than 100-fold;[13] quinidine extends DXM's half-life from 2–3 hours to over 16 hours.[9] These interactions are therapeutically exploited in approved formulations but are dangerous at recreational doses.
Dissociative synergy
PCP acts at the same brain receptor site as DXM. Combined use produces extreme, unpredictable dissociation with additive effects throughout the central nervous system.
Drug testing note
DXM is not detected by standard opioid drug screens. Some immunoassay panels may misidentify it as PCP due to structural similarities.[1]
Contraindications
7 known- MAOI use (absolute): Any current or recent (within 14 days) MAOI use is an absolute contraindication due to fatal serotonin syndrome risk.[8]
- Serotonergic medication use (relative to absolute): SSRIs, SNRIs, tramadol, and other serotonergic drugs substantially increase serotonin syndrome risk. Agents that also inhibit CYP2D6 (paroxetine, fluoxetine) create compounded risk.
- CYP2D6 poor metabolizer status (relative): Known poor metabolizers face dramatically elevated plasma DXM levels at any dose, increasing all adverse effects.
- Hepatic impairment (relative): Reduced liver metabolism may increase DXM accumulation, though substance-specific data are limited.citation needed
- Psychotic spectrum disorders (relative): NMDA antagonism can precipitate or worsen psychotic symptoms, particularly at high doses.[7]
- Respiratory compromise (relative): High-dose DXM can depress breathing, particularly combined with other sedatives.[8]
Harm Reduction[edit]
Forms & Identification
DXM is available as syrups, capsules, tablets, and powder-filled gelcaps. The critical concern is not DXM itself but the other active ingredients in combination products. Many cough and cold formulations contain acetaminophen (paracetamol), which causes severe liver damage at quantities consumed when DXM is taken at supratherapeutic doses.
Only products listing DXM as the sole active ingredient should be considered if DXM is being used outside its labeled indication. This is the single most important harm reduction measure — more emergency presentations involve co-formulated ingredients than DXM itself.
Guidelines
- Verify the product contains DXM as the sole active ingredient — no acetaminophen, no antihistamines, no guaifenesin
- Start with a low dose and wait at least 2 hours before considering redosing — onset is slow and unpredictable
- CYP2D6 metabolizer status dramatically affects intensity; individuals who have unusually strong reactions to normal doses may be poor metabolizers
- Have a sober companion present, particularly at doses above mild stimulant effects
- Keep the environment physically safe — DXM impairs coordination and spatial awareness at moderate-to-high doses
- Do not drive or operate machinery for the full duration plus recovery time
- Stay hydrated with small sips; do not force fluids during nausea
Set & Setting
DXM's long duration and dose-dependent escalation into deep dissociation make environment and mental preparation especially important. A safe, comfortable indoor space with a sober, trusted companion is strongly advisable — particularly at higher doses, where mobility and spatial awareness are significantly impaired.
Arranging the space to minimize fall hazards and keeping water accessible is practical preparation for a substance that frequently causes nausea and overheating. The extended timeline means planning for an entire day or evening without obligations.
Aftercare & integration. DXM's extended duration means aftereffects can persist well into the following day. Low-demand rest, adequate hydration, and light nutrition support recovery. Cognitive fogginess, emotional flatness, or mild dissociative feelings for 24–48 hours after use are commonly reported and typically resolve without intervention.
For those who experienced intense or unsettling dissociation, grounding techniques help re-establish embodied presence — physical contact with textured objects, cold water on the face, focused breathing, naming objects in the immediate environment. Talking through the experience with a trusted person can aid processing, particularly if the experience involved disturbing content.
Recovery & Support
Chronic DXM use can produce psychological and physical dependence with a recognized withdrawal. Those who find themselves using DXM compulsively, needing escalating doses for the same effect, or experiencing anxiety, insomnia, or low mood when stopping should consider professional support.
SAMHSA's National Helpline (1-800-662-4357) provides free, confidential referrals in the United States. Online peer support communities exist, though professional assessment is recommended for anyone experiencing dependence symptoms.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Mild nausea, dizziness, and confusion at low doses are common and generally self-limiting. Seek immediate help for: seizures, loss of consciousness or inability to be roused, extremely high body temperature (skin hot to the touch), rigid or jerking muscles (possible serotonin syndrome), severely slowed or stopped breathing, or chest pain.
Immediate steps:
- 1. Call emergency services if the person is unconscious, seizing, or showing signs of serotonin syndrome
- 2. Place an unconscious but breathing person on their side (recovery position) to prevent choking
- 3. Do not induce vomiting
- 4. Do not leave the person alone
- 5. Remove excess clothing if overheating; cool with damp cloths if body temperature is dangerously high
- 6. Monitor breathing continuously until help arrives
What to tell the dispatcher: Name the substance (dextromethorphan/DXM), estimated amount, time of ingestion, any other substances or medications involved, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
Legal Status[edit]
Dextromethorphan occupies an unusual regulatory position: widely available as an OTC medication in most jurisdictions and federally unscheduled in the United States, but subject to targeted age-restriction legislation due to its documented recreational misuse potential.
In the United States, DXM is not listed under the Controlled Substances Act and carries no federal age restriction for purchase.[11] Over 20 individual states have enacted laws restricting sale of DXM-containing products to individuals under 18, with some states requiring ID verification for purchasers appearing under 25–27.[11]
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States (federal) | Unscheduled | Not listed in CSA; OTC without federal age restriction[11] |
| United States (20+ states) | Age-restricted OTC | Sale restricted to individuals 18+; ID verification required[11] |
| United Kingdom | General sale | Available OTC without restriction[22] |
| Canada | OTC | Available without prescription[22] |
| Australia | Schedule 2 (Pharmacy Medicine) | Restricted OTC availability under TGA scheduling[22] |
| Russia | Schedule III controlled substance | Controlled; not available OTC[22] |
| Sweden | Unavailable | Not marketed[22] |
| Norway | Unavailable | Not marketed[22] |
| Denmark | Prescription only | Available by prescription[22] |
Safety[edit]
- Acute toxicity
- Moderate
- Chronic toxicity
- Moderate
- Withdrawal
- Mild
- Tolerance buildup
- moderate
- Tolerance reset
- 10 days
- Physical
- Low
- Psychological
- Moderate
- Compulsive redosing
- Low
- Dose escalation
- Moderate
- Cross-tol.
- ketamine · PCP · nitrous oxide
Toxicity
No human lethal dose has been established for DXM. The compound has a relatively wide margin between therapeutic antitussive doses (15–30 mg) and doses producing serious toxicity.
Toxicity thresholds
Evidence-based guidelines establish the following clinical thresholds for DXM ingestion[26]:
- Above 4 mg/kg: Up to 64% of people experience psychoactive effects
- 5–7.5 mg/kg: Increased monitoring recommended
- Above 7.5 mg/kg: Emergency department referral recommended
Common effects at doses above 4 mg/kg include euphoria, nausea and vomiting, involuntary eye movement, and dizziness.[8]
Severe overdose
At high doses, DXM toxicity combines dissociative, serotonergic, and sedative features.[8] Serotonin syndrome is the most dangerous acute risk, particularly with serotonergic co-medications. Other severe outcomes include respiratory depression (especially with sedative combinations), dangerous overheating from agitation, and muscle breakdown from prolonged seizures or agitation.
Published cases document survival from massive ingestions — including 5,600 mg producing prolonged seizures with full recovery by day 9[27] and over 100 tablets causing shock and convulsions requiring intensive care[28] — but these outcomes required aggressive hospital intervention.
CYP2D6 and toxicity
CYP2D6 poor metabolizers and people taking CYP2D6-inhibiting medications (paroxetine, fluoxetine, bupropion, quinidine) accumulate far higher DXM plasma levels from the same dose, dramatically increasing toxicity risk. A dose tolerated by an extensive metabolizer may produce life-threatening toxicity in a poor metabolizer.
Psychological risks
High-dose DXM can produce visual hallucinations, paranoid delusions, severe agitation, and disorientation.[8] Chronic misuse is associated with sustained psychosis, depression, and cognitive impairment.[6] The risk of psychological disturbance is amplified in individuals with pre-existing psychiatric conditions, particularly psychotic spectrum disorders.
Tolerance & dependence
Tolerance develops with repeated use. Cross-tolerance occurs with other NMDA antagonist dissociatives (ketamine, PCP). Community-reported timelines — buildup with prolonged use, roughly 5-day half-life, approximately 1.5-week full reset — have not been validated in controlled studies.citation needed
Physical and psychological dependence with chronic DXM use is documented, including withdrawal syndromes consistent with NMDA antagonist discontinuation.[6][7] DXM engages reward circuitry and produces tolerance and withdrawal — the hallmarks of abuse liability. In animal models, DXM modulates opioid and nicotine dependence behaviors, suggesting bidirectional interaction with addiction systems.[29]
Drug Interactions
DXM's multi-target pharmacology creates interaction risks through both pharmacodynamic (additive drug effects) and pharmacokinetic (altered metabolism) mechanisms.
Serotonergic interactions
DXM's SERT inhibition makes any serotonergic co-medication a potential trigger for serotonin syndrome. MAOIs are an absolute contraindication — the combination causes catastrophic serotonin accumulation with documented fatalities, requiring a minimum 14-day washout.[8][26]
SSRIs and SNRIs carry significant risk, compounded when the SSRI also inhibits CYP2D6 (paroxetine, fluoxetine), creating both pharmacodynamic and pharmacokinetic amplification.[6][30] Tramadol and MDMA pose serious serotonin syndrome risk through additive serotonergic mechanisms.
CNS depressant interactions
Alcohol, GHB/GBL, benzodiazepines, and opioids produce additive sedation and respiratory depression with DXM. Dissociative impairment of protective reflexes (cough, gag) amplifies aspiration risk during sedation.
Pharmacokinetic interactions
Strong CYP2D6 inhibitors dramatically increase DXM plasma levels. Bupropion raises DXM exposure more than 100-fold;[21] quinidine extends DXM half-life from 2–3 hours to over 16 hours.[9] While these interactions are therapeutically exploited in approved formulations, they are dangerous when DXM is used recreationally at supratherapeutic doses.
Dissociative synergy
PCP acts at the same NMDA binding site as DXM. Combined use produces extreme, unpredictable dissociation with additive CNS effects.
Drug testing note
DXM is not detected by standard opioid drug screens. Some immunoassay panels may misidentify it as PCP due to structural similarities.[1]
Contraindications
7 known- MAOI use (absolute): Any current or recent (within 14 days) MAOI use is an absolute contraindication due to fatal serotonin syndrome risk.[8]
- Serotonergic medication use (relative to absolute): SSRIs, SNRIs, tramadol, and other serotonergic drugs substantially increase serotonin syndrome risk. Agents that also inhibit CYP2D6 (paroxetine, fluoxetine) create compounded risk.
- CYP2D6 poor metabolizer status (relative): Known poor metabolizers face dramatically elevated plasma DXM levels at any dose, increasing all adverse effects.
- Hepatic impairment (relative): Reduced liver metabolism may increase DXM accumulation, though substance-specific data are limited.citation needed
- Psychotic spectrum disorders (relative): NMDA antagonism can precipitate or worsen psychotic symptoms, particularly at high doses.[6]
- Respiratory compromise (relative): High-dose DXM can depress breathing, particularly combined with other sedatives.[8]
Harm Reduction[edit]
Forms & Identification
DXM is available in numerous OTC formulations — syrups, capsules, tablets, and powder-filled gelcaps. The critical identification concern is not the DXM itself but the other active ingredients in combination products. Many cough and cold formulations contain acetaminophen (paracetamol), guaifenesin, antihistamines (chlorpheniramine, doxylamine), or decongestants alongside DXM. Acetaminophen poses severe liver damage risk at the quantities consumed when DXM is taken at supratherapeutic doses.
Only products listing DXM as the sole active ingredient should be considered if DXM is being used outside its labeled indication. This is the single most important harm reduction measure for DXM — more emergency presentations involve co-formulated ingredients than DXM itself.
Guidelines
- Verify the product contains DXM as the sole active ingredient — no acetaminophen, no antihistamines, no guaifenesin
- Start with a low dose and wait at least 2 hours before considering redosing — onset is slow and unpredictable
- CYP2D6 metabolizer status dramatically affects intensity; individuals who have unusually strong reactions to normal doses may be poor metabolizers
- Have a sober companion present, particularly at doses above mild stimulant effects
- Keep the environment physically safe — DXM impairs coordination and spatial awareness at moderate-to-high doses
- Do not drive or operate machinery for the full duration plus recovery time
- Stay hydrated with small sips; do not force fluids during nausea
Set & Setting
DXM's long duration and dose-dependent progression through increasingly profound dissociation make environment and mental preparation particularly important. A safe, comfortable indoor space with a sober, trusted companion present is strongly advisable, especially at higher doses where mobility and spatial awareness are significantly impaired.
Arranging the space to minimize fall hazards and keeping water accessible is practical preparation for a substance that frequently causes nausea and overheating. The extended timeline means planning for an entire day or evening without obligations.
Aftercare & integration. DXM's extended duration means aftereffects can persist well into the following day. A period of low-demand rest, adequate hydration, and light nutrition supports recovery. Cognitive fogginess, emotional flatness, or mild dissociative feelings for 24–48 hours after use are commonly reported and typically resolve without intervention.
For those who experienced intense or unsettling dissociative states, grounding techniques — physical contact with textured objects, cold water on the face, focused breathing, naming objects in the immediate environment — help re-establish embodied presence. Talking through the experience with a trusted person can aid processing, particularly if the experience involved disturbing content.
Recovery & Support
Chronic DXM use can produce psychological and physical dependence with a recognized withdrawal. Individuals who find themselves using DXM compulsively, escalating doses to achieve the same effects, or experiencing withdrawal symptoms (anxiety, insomnia, dysphoria) when stopping should consider professional support.
SAMHSA's National Helpline (1-800-662-4357) provides free, confidential referrals in the United States. Online peer support communities exist, though professional assessment is recommended for anyone experiencing dependence symptoms.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Mild nausea, dizziness, and confusion at low doses are common and generally self-limiting. Seek immediate help for: seizures, loss of consciousness or inability to be roused, extremely high body temperature (skin hot to the touch), rigid or jerking muscles (possible serotonin syndrome), severely slowed or stopped breathing, or chest pain.
Immediate steps:
- 1. Call emergency services if the person is unconscious, seizing, or showing signs of serotonin syndrome
- 2. Place an unconscious but breathing person on their side (recovery position) to prevent choking
- 3. Do not induce vomiting
- 4. Do not leave the person alone
- 5. Remove excess clothing if overheating; cool with damp cloths if body temperature is dangerously high
- 6. Monitor breathing continuously until help arrives
What to tell the dispatcher: Name the substance (dextromethorphan/DXM), estimated amount, time of ingestion, any other substances or medications involved, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
Legal Status[edit]
Dextromethorphan occupies an unusual regulatory position: a widely available OTC medication with documented recreational misuse potential that remains federally unscheduled in most jurisdictions. Regulatory responses have focused on age restriction rather than scheduling, reflecting DXM's legitimate therapeutic utility and its growing role in FDA-approved psychiatric formulations.
In the United States, DXM is not listed under the Controlled Substances Act and carries no federal age restriction for purchase.[11] Over 20 individual states have enacted laws restricting sale of DXM-containing products to individuals under 18, with some states requiring identification verification for any purchaser appearing under 25–27 years old.[11]
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States (federal) | Unscheduled | Not listed in CSA; OTC without federal age restriction[11] |
| United States (20+ states) | Age-restricted OTC | Sale restricted to individuals 18+; ID verification required[11] |
| United Kingdom | General sale | Available OTC without restriction[31] |
| Canada | OTC | Available without prescription[31] |
| Australia | Schedule 2 (Pharmacy Medicine) | Restricted OTC availability under TGA scheduling[31] |
| Russia | Schedule III controlled substance | Controlled; not available OTC[31] |
| Sweden | Unavailable | Not marketed[31] |
| Norway | Unavailable | Not marketed[31] |
| Denmark | Prescription only | Available by prescription[31] |
Frequently asked questions
What is Dextromethorphan?
Dextromethorphan is a morphinan dissociative and OTC antitussive acting as an NMDA antagonist, sigma-1 agonist, and serotonin reuptake inhibitor. First approved by the FDA in 1958, it has since gained approval as a component of treatments for pseudobulbar affect and major depressive disorder.
How long does Dextromethorphan last?
Total duration by route of administration — Oral: 8 – 12 hours. Ranges vary with dose and individual factors; see the duration table for onset, peak, and after-effect phases.
Where can I find dosage information for Dextromethorphan?
Psychedex publishes a dosage table for Dextromethorphan on this page covering these routes of administration: oral. Dose values are presented only in that table, always alongside their route of administration.
What are dangerous combinations with Dextromethorphan?
The highest-severity documented interactions for Dextromethorphan: Benzodiazepines, Barbiturates (Lethal), GHB, Baclofen (Lethal), GHB, GBL (Lethal), Local anesthetics (Lethal), 5-HTP, Tryptophan (Dangerous). See the interactions section for the full list with mechanisms and severity levels.
Is Dextromethorphan addictive?
Psychedex records tolerance and dependence data rather than a yes/no rating. Recorded tolerance indicators for Dextromethorphan: tolerance builds moderate; full reset takes 10 days; cross-tolerance develops with ketamine, PCP, nitrous oxide, memantine. See the article's dependence and safety sections for recorded dependence data.
experience reports
No experience reports yet. Be the first to contribute.
First-person accounts of subjective effects, timing, and outcomes — submitted for harm reduction.
references
- [1]
- [2]
- [3] ^abWerling LL, Keller A, Frank JG, Nuwayhid SJ (2007) A comparison of the binding profiles of dextromethorphan, memantine, fluoxetine and amitriptyline: treatment of involuntary emotional expression disorder — Experimental Neurology PMID:17689532
- [4] ^abcdMutschler J, Koopmann A, Grosshans M, Hermann D, Mann K, Kiefer F (2010) Dextromethorphan withdrawal and dependence syndrome — Deutsches Arzteblatt International doi:10.3238/arztebl.2010.0537
- [5] ^abMuneer MA, Tariq I, Zulfiqar E, et al. (2026) Efficacy and safety of dextromethorphan/quinidine in treating pseudobulbar affect: A systematic review and network meta-analysis — Neurological Sciences doi:10.1007/s10072-025-08640-7
- [6] ^abMcIntyre RS, Jain R (2024) Glutamatergic Modulators for Major Depression from Theory to Clinical Use — CNS Drugs doi:10.1007/s40263-024-01114-y
references
- [1]
- [2]
- [3] ^abcWerling LL, Keller A, Frank JG, Nuwayhid SJ (2007) A comparison of the binding profiles of dextromethorphan, memantine, fluoxetine and amitriptyline: treatment of involuntary emotional expression disorder — Experimental Neurology PMID:17689532
- [4] ^abMuneer MA, Tariq I, Zulfiqar E, et al. (2026) Efficacy and safety of dextromethorphan/quinidine in treating pseudobulbar affect: A systematic review and network meta-analysis — Neurological Sciences doi:10.1007/s10072-025-08640-7
- [5] ^abMcIntyre RS, Jain R (2024) Glutamatergic Modulators for Major Depression from Theory to Clinical Use — CNS Drugs doi:10.1007/s40263-024-01114-y
- [6]