Dextromethorphan, or DXM, is an over-the-counter cough suppressant found in the majority of nonprescription allergy, cold, and flu medications. At high doses, DXM acts as a powerful dissociative with effects similar to ketamine and PCP. Like other dissociative anesthetics, DXM is an NMDA antagonist but differs in that it also acts as a sigma receptor agonist and serotonin-norepinephrine reuptake inhibitor. Its effects manifest in a nonlinear fashion that is often described in terms of qualitatively different stages, or “plateaus.” DXM was first synthesized in the late 1940s and tested in a CIA-funded program in the 1950s as an alternative to the opiate cough suppressant codeine. It was approved by the FDA for medical use in 1953 and began to see recreational use by the next decade.
Table of Contents
- Overview
- History
- Legality
- Pharmacology
- Effects
- Uses
- DXM Today
- DXM FAQ
1. Overview
DXM is the main active ingredient found in nearly 90% of over-the-counter cough and cold medicines. Initially, DXM was developed and researched as an alternative to codeine, an opioid cough suppressant. In contrast to codeine, DXM provides effective cough suppression without analgesia, strong sedation, and respiratory depression. At doses many times higher than the therapeutic dose range, DXM is used as a powerful dissociative hallucinogen. When used recreationally, DXM has a complex pharmacological and effect profile that resembles other dissociative drugs such as PCP, ketamine, MXE, and nitrous.
What is DXM?
DXM is a semisynthetic antitussive medication found in hundreds of over-the-counter cold medications around the world. It is best known by its trade name, Robitussin, but is commonly found in other cough medicines such as Nyquil, Benylin DM, Coricidin Cough and Cold, and many more. Among other mechanisms of action, DXM and its major metabolite dextrorphan produce its dissociative effects by antagonizing the glutamatergic NMDA receptor.
It is typically found as dextromethorphan hydrobromide (DXM HBr), a water-soluble salt made by reacting dextromethorphan with hydrobromic acid. However, it can also be found as dextromethorphan polistirex, a time-release formulation that is intended for longer duration cough suppression. The majority of people who use DXM recreationally favor the hydrobromide salt form.
Dextromethorphan (DXM)
Dextromethorphan is a semisynthetic morphine derivative with a chemical formula of C18H25NO. Similar to codeine and morphine, it belongs to a class of psychoactive compounds known as the morphinans. Unlike other morphinans, however, it does not bind to opiate receptors in the brain. DXM is the dextrorotatory enantiomer of methorphan, a synthetic analog of codeine. It is a stereoisomer of levomethorphan, a controlled opioid analgesic.
Street Names
- Robo
- DM
- Dex
- Tussin
- Poor man’s PCP
- Triple C/CCC (Coricidin HBP)
- Skittles (Coricidin HBP)
- Robotripping (the experience)
- Dexing (the experience)
Ways to Consume DXM
DXM can be found over-the-counter at drug stores and in pure form from online chemical suppliers. Users almost always consume it orally. In pure form, DXM is found as a white powder that’s used orally and, rarely, intranasally. In over-the-counter formulations, it can be found in a variety of forms, including:
- Syrups
- Lozenges
- Capsules
- Tablets
- Spray
When used recreationally, DXM should be the only active ingredient in the formulation. This is because many of the cough and cold medicines contain other active ingredients. This includes guaifenesin, acetaminophen, and chlorpheniramine, all of which can be toxic or fatal when taken in large amounts.
2. History
Modern Day Discovery
The modern discovery of DXM originates with the synthesis of the racemic parent compound, racemorphan. The Swiss pharmaceutical company Hoffmann-La Roche patented racemorphan in 1950 and resolved its l- and d-isomers two years later. Research in the early 1950s discovered that the d-isomer (dextromethorphan) in particular showed potent antitussive activity, and demonstrated less analgesia than the l-isomer, levomethorphan. By 1954, the CIA tested dextromethorphan in a program they funded, known as MKPilot, in the hopes of finding a nonaddictive and less sedating alternative to codeine. After this research supported its safety and efficacy in suppressing coughs, the FDA approved it in 1958 as an over-the-counter antitussive.
Starting in the 1960s, DXM became available over-the-counter in tablet form under the trade name Romilar. By the mid-1960s, non-medical use and misuse of DXM began to surface. This eventually led to the commercial removal of Romilar in the early 1970s. Romilar was then replaced by DXM-containing cough syrup, which was thought to reduce the rates of recreational use since users would have to swallow large amounts of the unpleasant-tasting syrup. Still, the recreational use of DXM was popular in the 1980s within certain subcultures, particularly the hardcore punk movement. Due to the accelerating “War on Drugs” within this decade, DXM may have been a legal alternative to lesser-available psychedelics.
Growing Recreational Use
The recreational use of DXM grew in the 1990s when widespread internet access allowed the purchased of pure DXM hydrobromide powder from online retailers in bulk. Around this time, online drug discussion forums became a popular medium where recreational users would describe their DXM experiences. In response to the rising non-medical use, the DEA convened two advisory committee meetings in the early 1990s, but came to no consensus on what actions to take. In 2010, an FDA panel voted against making DXM a scheduled substance, believing that the public health and economic benefits outweighed the abuse potential of the drug.
3. Legality
DXM was not included in the 1970 Controlled Substances Act, despite being an analog of the Schedule II opiate levomethorphan. In addition, it had been excluded from the 1961 Single Convention on Narcotic Drugs.
Legality in the United States
In the United States, DXM is unscheduled and is available for purchase over-the-counter in pharmacies. This means DXM is legal to buy, possess, and ingest without a license or prescription. Over-the-counter sales are regulated by the Food and Drug Administration.
However, a number of states and distributors have implemented restrictions on its sale. This includes keeping the drug behind the counter, limiting purchasable quantities, requiring purchaser signatures, and requiring the purchaser to be over the age of 18.
Where is DXM Legal?
Around the world, the legality of DXM is treated similarly as in the United States. The exceptions are a handful of countries that require a prescription, including Singapore, Hong Kong, Greece, Turkey, Switzerland, and Sweden.
In Russia, DXM is a Schedule III controlled substance and is therefore regulated in a similar manner as benzodiazepines and barbiturates. As of 2014, single-component DXM is illegal in Indonesia.
4. Pharmacology
After oral dosing, DXM is absorbed into the bloodstream within the GI tract and readily crosses the blood-brain barrier, reaching peak serum levels a few hours later. The mechanisms of action of DXM aren’t completely understood, but five receptor systems are known to be involved. It is thought to primarily function as an NMDA antagonist. It binds to the same site on the NMDA receptor as PCP and ketamine. The blockade of these glutamate receptors reduces excitatory signaling in the central nervous system, leading to powerful dissociative effects.
Additionally, DXM acts as a nicotinic acetylcholine antagonist, a sigma-1 receptor agonist, and nonselective serotonin-norepinephrine reuptake inhibitor. Agonism of the sigma receptors is responsible for DXM’s antitussive properties, and may contribute in part to its potential antidepressant action.
In the liver, an enzyme known as CYP2D6 processes DXM into a metabolite called dextrorphan, or DXO. DXO is a stronger NMDA antagonist and is therefore responsible for most of the dissociative effects. If DXM is co-administered with grapefruit juice or low doses of quinidine, this inhibits the first-pass metabolism of DXM into DXO, thereby providing greater bioavailability.
Toxicity
Drug toxicity is commonly measured with a value known as the median lethal dose or LD-50. The LD-50 is defined as the dose that is lethal for half of a group of tested animals. For rats, the LD-50 of DXM is approximately 116 mg/kg, while in mice it is 210 mg/kg. The exact LD-50 in humans is unknown, but it is estimated to be in the range of 50–500 mg/kg.
Fatal DXM toxicity is rare when DXM is consumed by itself. A 1988 case report by Rammer and colleagues described two fatal DXM intoxications in Sweden. However, the exact lethal doses were uncertain. Similar to other NMDA antagonists, heavy, chronic use of DXM may be associated with neurotoxicity, though this hasn’t been confirmed in studies.
By far the biggest danger relating to DXM toxicity is the co-ingestion of other active ingredients found in DXM-containing formulations. In particular, acetaminophen at high doses can cause severe liver damage and can result in a fatal overdose. High doses of guaifenesin, an expectorant commonly found in DXM-containing products, can bring on severe nausea and vomiting. The antihistamine chlorpheniramine maleate, a common ingredient in Coricidin Cough and Cold, can result in seizures and loss of consciousness at high doses.
Interactions
DXM is dangerous to combine with other serotonergic substances. This includes monoamine oxidase inhibitors (MAOIs), selective serotonin reuptake inhibitors (SSRIs), and tricyclic antidepressants. DXM may also pose life-threatening reactions when taken with prescription and non-prescription antihistamines such as diphenhydramine and terfenadine. These combinations can lead to a potentially fatal condition known as serotonin syndrome, which is characterized by sweating, tremor, hyperthermia, confusion, anxiety, agitation, and coma. MDMA and 5-HTP may also increase the chance of serotonin syndrome when co-ingested with DXM, so avoid these combinations.
DXM may also dangerously potentiate other CNS depressants. Do not combine it with GHB, alcohol, opioids, tramadol, or benzodiazepines. These combinations can increase the chances of dangerous respiratory depression and unconsciousness.
Common DXM Dose
Light-to-common doses (100–400 mg) are popular for recreational use, while strong-to-heavy doses (300–1500 mg) are well-suited for spiritual work and self-exploration. It’s always best to try a low dose first, then slowly titrate up to gauge one’s individual reaction. Note: a dose above roughly 1700–2000 mg carries a risk of death.
| Oral Dose for DXM HBr (milligrams) | |
| Light | 100–200 mg |
| Common | 200–400 mg |
| Strong | 300–600 mg |
| Heavy | 600–1500 mg |
Overdose
Generally, the risk of a DXM overdose begins to occur at doses equal to or larger than 15 mg/kg. For a 150-pound individual, this amounts to a little over 1000 mg. Overdoses are associated with symptoms such as hypertension, rapid heartbeat, blurred vision, muscle spasms, blackouts, vomiting, hallucinations, acute psychosis, slow breathing, and seizures. There is also a possibility of serotonin syndrome if DXM is used in combination with a serotonergic substance.
DXM overdoses are not usually life-threatening, but they are medical emergencies. In most cases, intravenous naloxone, an opioid antagonist, is used to treat an overdose.
Safety
DXM is known for its high margin of safety when it’s used by itself in moderation and under optimal set and setting. In general, a rule of thumb for recreational use is to wait at least two weeks before another DXM trip. High doses carry the most psychological and physiological risk, so users should never exceed 15 mg/kg. Heavy, frequent use carries the possibility of neurotoxicity as well as the development of tolerance and psychological dependence. In users who are dependent, stopping DXM abruptly can result in withdrawal symptoms such as fatigue, apathy, flashbacks, constipation, insomnia, and anhedonia.
When using recreationally, avoid products that contain DXM with other active ingredients, including expectorants, antihistamines, analgesics, and decongestants. High doses of these ingredients, particularly acetaminophen, can be life-threatening. Never combine DXM with other serotonergic drugs and antihistamines, as these combinations can result in serotonin syndrome.
DXM is known to produce highly variable reactions from person to person. It’s always best to start with a low dose and gauge one’s individual reaction. Adverse reactions to DXM, either from allergic or sensitive responses, have also been reported by many recreational users. DXM should not be used by those with a history of mental illness, epilepsy, seizures, liver/kidney disorders, hypertension, heart ailments, and ulcers. Dissociatives can pose dangers to developing fetuses, so DXM should be avoided by women who are pregnant or nursing.
5. Effects
At low doses, the DXM high is comparable to alcohol, while high doses can produce effects that resemble a high dose of ketamine. In general, the DXM experience varies greatly from individual to individual. Approximately a third of individuals enjoy the DXM trip enough to repeat the experience.
DXM’s effects typically begin between 20 minutes and 1 hour after ingestion. The experience peaks 1.5–3 hours after onset, and lasts between 4–8 hours. Some users report a DXM hangover the next day, while others describe a positive afterglow that can last up to a few days.
The effect profile of a DXM trip is not linearly dose-dependent, but instead manifests in distinct stages or “plateaus.” Each of the plateaus consists of a different set of effects brought on within defined dose ranges. The following sections overview the physiological and psychological effects of DXM hydrobromide, the most commonly consumed form in recreational settings.
Psychological Effects
Plateau 1 occurs at approximately 100–200 mg (1.5–2.5 mg/kg). Many users overshoot plateau 1 and end up in the next plateau or higher. Psychological effects generally resemble alcohol intoxication, and can include:
- Euphoria
- Mood elevation
- Stimulation
- Increased sociability
- Disinhibition
- Increased music appreciation
- Emotion amplification
- Time distortion
- Depth perception impairment
Plateau 2 is attained at doses between 200–400 mg (2.5–7.5 mg/kg). This plateau is perhaps the most common recreational dose range. Psychological effects may include:
- Euphoria
- Closed-eye hallucinations
- Music enhancement
- Dream-like detachment
- Visual frame rate suppression
- Increased introspection
- Vivid imagination
In Plateau 3, the effects of DXM closely resemble a ketamine trip and may produce profoundly spiritual and introspective experiences. This plateau is reached at doses between 400–600 mg (7.5–15 mg/kg). The psychological effects here can include:
- Dissociation
- Internal hallucinations
- Auditory hallucinations
- Slow reaction
- Profound introspective experiences
- Visual flanging
- Ego death
- Short-term memory impairment
- Spontaneous recall of memories
- Cognitive dysphoria
Plateau 4 occurs at doses between 600–1500 mg (roughly 15–20 mg/kg). It is likened to the effects of a high dose of ketamine and carries the greatest psychological risk. In addition to the effects at plateau 3, plateau 4 can psychologically consist of:
- Profound dissociation
- Extreme sedation
- External hallucinations
- Out of Body Experiences (OBEs)
- Amnesia
- Contact with entities
- Delusions
- Delirium
Physiological Effects
In the lower plateaus (1 and 2), physiological effects can include:
- Pupil dilation
- Body load
- Spontaneous bodily sensations
- Feelings of bodily lightness
- Balance disturbances
- Robotic gait (“robo-walking”)
- Fine motor coordination difficulties
- Skin sensitivity
- Nausea
The upper plateaus (3 and 4) can produce more incapacitating physical effects, including:
- Incoordination
- Loss of body control
- Dizziness
- Disconnection from tactile and internal sensations
- Feelings of physical alteration (merging with objects)
Common Side Effects
DXM can dose-dependently bring on a wide array of side effects. These side effects depend on a number of factors, such as the dose consumed, user body weight, idiosyncratic reactions, and tolerance levels. Common side effects may include:
- Increased body temperature
- Increased heart rate
- Increased blood pressure
- Urinary retention
- Appetite suppression
- Fever
- Nausea
- Vomiting
- Diarrhea
- Muscle spasms
- Itching
- Sweating
- Confusion
- Drowsiness
- Panic
- Acute psychosis (high doses)
Tolerance
Regular users are known to develop tolerance to DXM’s effects, where increasingly larger doses are required to attain the same effects. Tolerance is more likely to develop when DXM is used frequently and in large amounts. In most cases, it takes up to a week to halve the tolerance, and 1–2 weeks for it to fully reverse.
Anecdotally, some frequent DXM users describe a chronic form of tolerance that may take at least several months to reverse. Because they act on the same receptor systems, DXM is cross-tolerant with other dissociatives, such as PCP and ketamine.
6. Uses
Recreationally
People have used DXM recreationally for over 50 years for its dissociative, stimulating, and sedating properties. Recreational use of DXM is known as “dexing,” “roboing,” and “robotripping,” in reference to the popular DXM-containing cough syrup, Robitussin.
The vast majority of recreational users are adolescents and young adults. They usually consume DXM orally in formulations containing solely DXM. They typically use it at home or in a similar safe space, usually in solitary settings or alongside a trip sitter. In contrast to many other drugs, DXM may be used recreationally due to its easy accessibility, relative affordability, and undetectability on standard drug tests. In addition, it maintains a high safety margin when used by itself and responsibly (e.g., in moderation and under proper set and setting).
Medically
DXM is primarily used as an antitussive to suppress coughs due to the common cold or flu. The average adult dose to suppress cough is 15–30 mg, used three to four times a day. DXM has also been investigated to treat a number of other conditions, including:
- Pseudobulbar affect (uncontrollable laughing or crying)
- Withdrawal symptoms from opioid use disorder
- Neuropathic pain
- Neurodegenerative disorders
7. DXM Today
Trends in Use
The recreational use of DXM appeared to be highest among teens in the early-to-mid 2000s and has since declined significantly, following purchasing restrictions and awareness campaigns. The 2019 Monitoring The Future survey conducted by the National Institute on Drug Abuse (NIDA) found that 2.8% of teens reported past-year recreational use of DXM-containing cough syrup. These rates have decreased by almost half since 2006, when the Monitoring the Future survey reported that 5.4% of teens used OTC cough syrup recreationally in the past year.
According to a 2018 paper by Karami and colleagues, intentional DXM abuse calls to poison control centers peaked in 2006, at 143.8 calls per million population. These rates declined 58.3% from 2006–2015 to 80.9 calls per million population. Currently, the recreational use of dextromethorphan accounts for roughly 6,000 emergency department visits per year in the United States.
Current Studies and Research
Since DXM blocks NMDA receptors and inhibits serotonin re-uptake, similarly to ketamine treatment and prescription antidepressants, clinical research is evaluating its potential antidepressant properties.
The biopharmaceutical company Axsome Therapeutics has recently completed a phase III clinical trial evaluating the efficacy of AXS-05, a medication containing bupropion and dextromethorphan, for treatment-resistant depression. Bupropion is an FDA-approved antidepressant that also increases the bioavailability of DXM by inhibiting the enzyme involved in its metabolism. The company is currently recruiting patients with major depressive disorder for a long-term, open-label study to assess its safety and efficacy.
Drug Testing Info
DXM is not detected on standard urine drug screenings. There are anecdotal reports that DXM can lead to false positives for PCP and opiates, though studies do not support the latter.
Further Resources
- The DXM FAQ by William White. This is a comprehensive guide to DXM, covering general information on DXM, the effects of the DXM experience, the neuropharmacology of DXM, trip reports, and much more.
8. DXM FAQ
What Does DXM Do?
At normal medicinal doses, DXM suppresses the cough reflex. Recreationally, DXM acts as an NMDA antagonist that produces dissociative, sedating, and stimulating effects, depending on the dose consumed.
Is DXM Stronger Than Ketamine?
Given their similar mechanism of action in the brain, DXM’s effects are comparable to those of ketamine. In particular, third and fourth plateau doses produce strong dissociative effects very similar to pre-anesthetic doses of ketamine. With that said, the DXM experience lasts longer, and generally produces more side effects, compared to ketamine.
How Long Does a DXM Trip Last?
The length of a DXM trip is dose-dependent and depends on the form of DXM ingested. DXM hydrobromide typically lasts 4–8 hours, while DXM polistirex can last anywhere from 6–12 hours. Generally, DXM hydrobromide is the most popular recreational form.
How Long Does DXM Stay in Your System?
DXM has an elimination half-life of approximately 4 hours. This means that after 20 hours, 97% of the drug will be eliminated from the body.
Is DXM Dangerous?
Yes, it can be. The dangers of DXM increase with increasing dose. The greatest (and most preventable) danger is consuming a formulation that contains DXM alongside other active ingredients that can be toxic or fatal when overdosed. DXM can also be dangerous to consume in combination with serotonergic drugs, including MAOIs and SSRIs.
When DXM is consumed by itself and in moderation, the greatest dangers are acute psychological effects, including psychotic breaks, mania, agitation, prolonged dissociation, depression, and bad trips. In susceptible individuals, DXM can cause allergic reactions due to its histamine-releasing properties.
Is DXM Addictive?
DXM is not known to be physically addictive. However, regular use can result in tolerance, cravings, and psychological dependence. Heavy, chronic users may experience unpleasant withdrawal symptoms upon cessation of the drug. These withdrawal symptoms aren’t well defined, but they have been reported to be similar to SSRI-induced withdrawals.
Can You Die from DXM?
Fatal overdoses from DXM alone are rare, but they have happened. DXM toxicity emerges at doses exceeding 15–20 mg/kg, or roughly 1–1.5 grams for a 70-kg person. Fatalities are rare, but when they occur, they are associated with respiratory depression.
Disclaimer: DXM is potentially categorized as an illegal drug. Reality Sandwich is not encouraging the use of this drug where it is prohibited. However, we believe that providing information is imperative for the safety of those who choose to explore this substance. This guide is intended to give educational content and should in no way be viewed as medical recommendations.
RS Contributing Author: Dylan Beard
Dylan Beard is a freelance science writer and editor based in the beautiful Pacific Northwest. After finishing his physics degree and dabbling in neuroscience research at UC Santa Barbara in 2017, he returned to his first love: writing. As a long-term fan of the human brain, he loves exploring the latest research on psychedelics, nootropics, psychology, consciousness, meditation, and more. When not writing, you can probably find him on hiking trails around Oregon and Washington or listening to podcasts. Feel free to follow him on Insta @dylancb88.
