|Summary sheet: Dextromethorphan|
|Common names||DXM, DMO, DM, Dex, Robitussin, Delsym, DexAlone, Duract|
|Routes of Administration|
Dextromethorphan (also known as robo, dex, DM, and DXM) is a dissociative substance of the morphinan class. DXM is the primary active ingredients in many common over-the-counter (OTC) cold and cough medicines. When exceeding approved doses, DXM produces dissociative effects similar to those of ketamine and phencyclidine (PCP). The pharmacology of DXM is not completely understood, but it is thought to act primarily by blocking NMDA receptors in the brain.
DXM was first reported in 1953 and approved for use as a cough suppressant in the United States in 1958. After its approval, it was introduced as an OTC medication under the name Romilar. As early as 1975, the popularity and extensive abuse of DXM was recognized, and Romilar was voluntarily removed from the OTC market. A few years later, companies began introducing various refined DXM products designed to deter abuse, such as including ingredients with an unpleasant taste. However, recreational use of DXM has persisted and is a considered a growing trend, particularly among teenagers seeking low cost and easily available highs.
Users commonly describe the experience of DXM as disorienting, bizarre, hallucinatory, and asocial. Notable effects include time distortion, bodily hallucinations, motor control loss, ego loss, and euphoria. It is often reported to produce a strong, uncomfortable body load with significant nausea. The effects and tolerability of DXM are highly variable between users which may be due to individual differences in the genes underlying metabolism. As a result, many users find the experience of DXM to be either unpleasant or neutral, while others report mystical-type experiences that facilitate self-reflection and personal growth.
The toxicity of DXM in high doses is unclear and has been the subject of controversy. There is some evidence that suggests NMDA antagonists may have neurotoxic effects when used in excess. Many cases of DXM dependence and abuse have been documented. It is strongly advised to use harm reduction practices if using this substance.
- 1 History and culture
- 2 Chemistry
- 3 Pharmacology
- 4 Subjective effects
- 4.1 Physical effects
- 4.2 Visual effects
- 4.3 Cognitive effects
- 4.4 Auditory effects
- 4.5 Disconnective effects
- 4.6 Multi-sensory effects
- 4.7 Transpersonal effects
- 4.8 Afterglow
- 4.9 Plateaus
- 4.10 Experience reports
- 5 Common usage
- 6 Toxicity and harm potential
- 7 Legal status
- 8 See also
- 9 External links
- 10 References
History and culture
The racemic parent compound of dextromethorphan, racemorphan, was first described in a Swiss and US patent application from Hoffmann-La Roche in 1946 and 1947, respectively. A patent was granted in 1950. A resolution of the two isomers of racemorphan with tartaric acid was published in 1952, and DXM was successfully tested in 1954 as part of US Navy and CIA-funded research on nonaddictive substitutes for codeine.
DXM was approved by the FDA in 1958 as an over-the-counter antitussive, or cough suppressant. As had been initially hoped, DXM was a solution for some of the problems associated with the use of codeine phosphate as a cough suppressant, such as sedation and opiate dependence, but like the dissociative anesthetics phencyclidine and ketamine, DXM later became associated with nonmedical use.
During the 1960s and 1970s, dextromethorphan became available in an over-the-counter tablet form by the brand name Romilar. In 1973, Romilar was taken off the shelves after a burst in sales because of frequent misuse, and was replaced by cough syrup in an attempt to cut down on abuse. The advent of widespread internet access in the 1990s allowed users to rapidly disseminate information about DXM, and online discussion groups formed around use and acquisition of the substance.
As early as 1996, DXM HBr powder could be purchased in bulk from online retailers, allowing users to avoid consuming DXM in syrup preparations. As of January 1, 2012, dextromethorphan is prohibited for sale to minors in the state of California, except with a doctor's prescription.
Dextromorphan is a dextrorotatory molecule of the morphinan class. It contains a phenanthrene core structure with one aromatic ring (benzene) bound to two saturated rings (cyclohexane). Additionally, it contains a saturated piperidine ring attached to R9 and R13 of the core structure. DXM is substituted at RN with a methyl group and at R3 with a methoxy group.
The pharmacology of DXM is not completely understood. In vitro studies suggest that the primary mechanism of action of DXM is blockade of N-methyl-D-aspartate (NMDA) receptors. NMDA receptors are a type of glutamate receptor; glutamate is the primary excitatory neurotransmitter. Blockade of NMDA receptors therefore interferes with excitatory signaling in the central nervous system. This mechanism of action is similar to ketamine and PCP. Rather than acting as a direct NMDA receptor antagonist itself, dextromethorphan acts as a prodrug of its much more potent metabolite dextrorphan, and this is the actual mediator of its dissociative effects.
At high doses, DXM can cause an increase in systolic and diastolic blood pressure along with an increase in heart rate. DXM also increases blood plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone.
|Binding Sites||Binding Affinity Ki (nM)|
DXM is O-demethylated into Dextrorphan (DXO / D-3-hydroxy-N-methylmorphinan) by the CYP2D6 enzyme. DXM is also N-demethylated into 3-methoxymorphinan (MEM / Morphinan) by the CYP3A4 enzyme and to a lesser extent CYP3A5.
Dextrorphan and 3-methoxymorphinan are both metabolized into 3-hydroxymorphinan. Dextrorphan is N-demethylated by CYP3A4 and 3-Methoxymorphinan is O-demethylated by CYP2D6. CYP2D6 O-demethylation is more effective than CYP3A4 N-demethylation.
Some people may be very fast metabolizers and others slow or even have this enzyme missing due to genetic variation. This contributes to the wide array of effects as this is the main factor for the levels of mainly DXM and DXO in the body. Enzyme disruption as well as CYP2D6 inhibitors also contribute to this effect.
Dextrorphan is produced by O-demethylation of dextromethorphan through the CYP2D6 enzyme and contributes to the psychoactive effects of dextromethorphan. It is pharmacologically similar to that of dextromethorphan (DXM). However, dextrorphan is much more potent as an NMDA receptor antagonist as well as much less active as a selective serotonin reuptake inhibitor. It is also about 3-fold less potent of a α3β4 nicotinic receptor antagonist than DXM and has a lower affinity for sigma-1 receptors.
|Binding Sites||Binding Affinity Ki (nM)|
3-Hydroxymorphinan (also known as 3HM) is produced by O-demethylation of 3-methoxymorphinan by CYP2D6 and metabolization of dextrorphan by CYP3A4 and CYP3A5. 3-Hydroxymorphinan exhibits neuroprotective and neurotrophic effects.
The effects listed below are based upon the subjective effects index and personal experiences of PsychonautWiki contributors. These effects should be taken with a grain of salt and will rarely (if ever) occur all at once, but heavier doses will increase the chances of inducing a full range of effects. Likewise, adverse effects become much more likely on higher doses and may include serious injury or death.
- Stimulation & Sedation - At lower, recreational doses, DXM is predominantly stimulating. However, it can produce waves of tiredness, or the desire to lay down with the eyes closed in a sleep-like state. As higher dosages are approached, the experience generally turns very sedating and lethargic, sometimes resulting in the user not moving at all.
- Perception of bodily lightness - This creates the sensation that the body is floating and has become entirely weightless. This effect is strangely stimulating and encourages physical activities at low to moderate dosages by making the body feel light and effortless to move.
- Spontaneous bodily sensations - The DXM "body high" is a sharp, pleasurable and warm tingling sensation which can be localized to the hands, feet, and head. In lower doses, it can produce an empowering stimulated sensation, at higher dosages a slight to heavy body load.
- Physical euphoria - This results in feelings of physical euphoria which range between mild pleasure to powerful, all-encompassing bliss.
- Appetite suppression - This can persist throughtout the next day.
- Changes in felt bodily form
- Motor control loss - A loss of gross and fine motor control alongside balance and coordination is prominent within DXM and becomes especially strong at higher dosages. One should be sitting down before the onset to prevent falling over and becoming injured.
- Spatial disorientation - A spinning sensation is commonly felt that can result in mild disorientation as if one were falling through a hole.
- Nausea - DXM can sometimes produce extreme nausea and vomiting, typically during the come up phase of the experience. This is more intense and consistent than the nausea produced by ketamine and MXE. This is likely not caused just by DXM itself, but rather by the medium which contains the DXM, which is usually syrup or gelatin capules. When pure DXM is consumed it is rare to experience nausea.
- Temperature regulation suppression
- Increased blood pressure
- Increased heart rate
- Increased perspiration - This is the result of a combination of increased bodily temperature and temperature regulation suppression.
- Muscle spasms
- Itchiness - This effect is colloquially known as "robo-itch". Many users never experience this effect while some individuals can experience it quite intensely. It is caused by histamine release.
- Cough suppression
- Pain relief
- Optical sliding
- Dizziness - At higher dosages this can result in incapability to willingly stand up.
- Gustatory hallucination
- Physical autonomy - At very high dosages some may find to awake in strange locations, sometimes while standing or performing actions with no recollection of events or how they got there.
- Tactile suppression - This partially to entirely suppresses sense of touch, creating feelings of numbness within the extremities. It is responsible for the anesthetic properties of this substance.
- Pupil dilation
- Gait alteration - This is a common effect on DXM and is commonly referred to as "robo walking". As with itchiness, some users may never experience this effect while others may experience it quite intensly.
- Peripheral vision enhancement - This effect usually only occurs at low doses.
- Frame rate enhancement - This effect is rare and occasionally experienced on the lower plateaus. It appears to be setting dependent.
- Double vision - This component is prevalent at moderate to heavy dosages and makes reading impossible unless one closes an eye.
- Pattern recognition suppression - This effect generally occurs at higher dosages and makes one unable to recognize and interpret perceivable visual data. Examples can include an inability to recognize faces or motion.
- Frame rate suppression - This is the so-called "flanging" effect, which at appropriately high doses can affect sight, sound and at higher levels phrases, faces and thinking.
- Nystagmus - At very high dosages one may be incapable of recognizing things such as movement of objects or human faces.
- Visual acuity suppression - Vision is reported to be very dream-like.
- After images
- Depth perception distortions
- Drifting - Visual drifting has been reported to occur on DXM, although it is uncommon. This effect is unrealistic in appearance. The distortions fast and smooth in motion, and are fleeting in appearance.
- Environmental cubism
- Environmental orbism
- Perspective distortions
- Scenery slicing
- Visual haze
- Visual stretching
The visual geometry produced by DXM can be described as very bright, colorful, psychedelic and intricate when compared to that of ketamine or MXE, but darker than psychedelics like LSD. It does not extend beyond level 4 and can be comprehensively described through its variations as intricate in complexity, algorithmic in style, synthetic in feel, unstructured in organization, brightly lit in lighting, multicoloured in scheme, glossy in shading, soft in edges, small in size, slow in speed, smooth in motion, equal in rounded and angular corners, immersive in-depth and consistent in intensity.
At high dosages, DXM can produce a full range of high level hallucinatory states in a fashion that is less consistent and reproducible than that of many other commonly used psychedelics. These effects include:
- External hallucination (autonomous entities; settings, sceneries, and landscapes; perspective hallucinations and scenarios and plots) - In comparison to other dissociatives, this effect can occur at heavy dosages, but is extremely infrequent in comparison to the same effect found within deliriants. It can be comprehensively described through its variations as delirious in believability, autonomous in controllability and solid in style. The most common theme for this effect to follow is one of experiencing and talking to friends around oneself when they are not actually present.
- Internal hallucination (autonomous entities; settings, sceneries, and landscapes; perspective hallucinations and scenarios and plots) - In comparison to other dissociatives, this effect can occur at heavy dosages, but is less common than the same effect found within psychedelics and deliriants, although can sometimes become very encompassing nonetheless. It can be comprehensively described through its variations as delirious in believability, fixed in style, equal in new experiences and memory replays in content, autonomous in controllability and solid in style.
The head space of DXM is often described as distinctly hallucinogenic, impairing, disorientating and generally less clear-headed in comparison to that of MXE and ketamine. The cognitive effects of DXM can be broken down into several separate subcomponents which are listed and described below:
- Analysis suppression
- Anxiety suppression or Anxiety - Although DXM typically suppresses anxiety, it is also able to produce it in certain conditions. Panic attacks can occur at heavy dosages.
- Conceptual thinking
- Cognitive euphoria - While states of cognitive euphoria are commonly reported, this effect can unpredictably manifest itself as cognitive dysphoria for no apparent reason, particularly at higher doses.
- Cognitive fatigue
- Creativity enhancement
- Decreased libido
- Déjà vu
- Delusion - This effect can occur spontaneously among some users and is more likely to occur at higher doses.
- Feelings of impending doom
- Disinhibition - This effect can be quite significant even at moderate dosages.
- Ego inflation
- Dream potentiation
- Emotion enhancement - Though this effect isn't as consistent as it is with other commonly used hallucinogens it is more prominent than with most dissociatives.
- Empathy, love, and sociability enhancement - This is commonly reported as being similar to but less prominent than with other commonly used entactogens such as MDMA or MDA.
- Immersion enhancement
- Increased libido - This is exclusively felt in low doses.
- Increased music appreciation - This effect can be very intense with DXM, especially at the lower plateaus. Listening to music greatly intensifies the experience and produces strong euphoria.
- Memory suppression
- Ego death
- Amnesia - This effect is usually only present with higher dosages, past the threshold for ego death (which can vary between people based on their individual metabolism). It can range from partial to complete memory loss of the experience. Generally, more dull parts of the experience tend to not be remembered at all. Frequent use can sometimes contribute to this, even for days after the experience.
- Focus suppression
- Motivation suppression
- Novelty enhancement
- Personal bias suppression - This effect is not usually as pronounced as it is with other more commonly used hallucinogens such as LSD or psilocin.
- Personal meaning enhancement - This effect is typically only present on the lower plateaus and varies in its believability and content.
- Thought deceleration
- Time distortion - Time while on DXM often feels very stretched out, for example, it may feel like hours have passed when in reality only ten minutes have passed. There also seems to be a general difficulty of what time certain events took place.
- Cognitive disconnection
- Physical disconnection - Although this effect is present, it is usually not as powerful or as consistent as with ketamine or PCP.
- Visual disconnection - This eventually results in the DXM's equivalent of the "K-hole" or more specifically, holes, spaces and voids alongside of structures.
- Synaesthesia - In its fullest manifestation, this is a very rare and non-reproducible effect. Increasing the dosage can increase the likelihood of this occurring, but seems only to be a prominent part of the experience among those who are already predisposed to synaesthetic states.
- The afterglow is a feeling that can occur within the 24 hours after the end of the experience. It can be described regarding its physical sensation as one of euphoria, rejuvenation, relaxation and a light bounciness. Regarding its cognitive effects, it often comes in the form as a loss of anxiety, feelings of content, and a noticeable increase in one's ability to appreciate music and other sensory stimuli that are sometimes accompanied with mild derealization or depersonalization.
The online DXM community categorizes the types of experiences that can result from oral DXM use into five "plateaus" which are characterized by qualitatively distinct effects.
First Plateau (1.5 - 2.5 mg/kg) - The effects felt in the first plateau are usually not very intense. They can include but are not limited to: cognitive euphoria, increased music appreciation, time distortion, pupil dilation, and stimulation. First plateau is often described as a "drunk" feeling.
Second Plateau (2.5 - 7.5 mg/kg) - Most DXM users consider this the to be the most recreational plateau. The second plateau is more sedating than stimulating, euphoria and visual disconnection are more intense. Additional effects of the second plateau can include but are not limited to: Wakefulness, physical euphoria, spatial disorientation. Many users of DXM do not proceed past the second plateau, as the desired effects are thought to be outweighed by the increasingly unpredictable adverse physical and cognitive effects as well as a more pronounced "body load".
Third Plateau (7.5 - 15 mg/kg) - The effects of the third plateau can include but are not limited to: sedation, nausea, memory suppression and ego death, auditory hallucinations, internal hallucinations, cognitive dysphoria, anxiety, delusions, and all the effects of the second plateau.
Fourth Plateau (15 - 20 mg/kg) - The effects of the fourth plateau can include but are not limited to external hallucinations, complete dissociation, and all the effects of the third plateau, with greater intensity. Doses of DXM in this range are very dangerous and have a high risk of injury and overdose, and are therefore advised against.
Fifth Plateau (also known as "Plateau Sigma") - A common method to experience the so-called "Plateau Sigma" is to take second plateau dose, followed by another second plateau dose three hours later, then at the peak of the second dose, take a fourth plateau dose. Plateau Sigma may also occur unintentionally from redosing. It is nearly always a very unpleasant and unpredictable experience. The experience can last from one day to four days. Plateau Sigma usually results in delirious hallucinations, dysphoria, delirium, psychosis, and anxiety. Plateau Sigma has a high potential to cause serotonin syndrome and is therefore strongly advised against.
Anecdotal reports which describe the effects of this compound within our experience index include:
- Experience:1000mg / 1200mg / 1400mg / 1600mg - heroic doses
- Experience:1064mgs - Fascinating DXM experience - Unusual effects
- Experience:250mg DXM - DXM Itch and Trip Report
- Experience:300mg DXM + 25mg DMT + Cannabis - A crazy night
- Experience:350mg DXM - A surprisingly profound experience
- Experience:354mg DXM, weed, nicotine - Descending into the void
Additional experience reports can be found here:
DXM is available in several different forms that can be found over the counter or online.
- Cough syrup is the most common form online and over the counter. Well-known brands include Benylin, DayQuil, Delsym, NyQuil, Robitussin, and Siltussin. Many of these products contain other medicines, including aspirin, acetaminophen, caffeine, guaifenesin or pseudoephedrine. Care should be taken when using these products to ensure that there is no overdose on other medicines in the DXM-containing product. Within the UK, Benylin dry coughs 7.5mg/5ml syrup (225mg dosage per 150ml bottle) is available behind the counter at every pharmacy. Generic brands are also available within these shops for a consistently lower price.
- Gel capsules and pills are available online and over the counter. Well-known brands include Benylin, Comtrex, Coricidin, DayQuil, Mucinex, NyQuil, and Robitussin. Many of these products contain other medicines, including aspirin, acetaminophen, caffeine, guaifenesin or pseudoephedrine. Care should be taken when using these products to ensure that there is no overdose on other medicines in the DXM-containing product.
- Pure powder is available online. This is the safest way to use DXM, as there is no danger of overdose from secondary chemicals.
Grapefruit juice is reported to be effective at potentiating and enhancing the effects of DXM. If one drinks approximately one glass of white grapefruit juice hourly the day before the trip, the effects will be considerably stronger and more intense. For users who are drinking store bought syrup, this is useful as it means drinking less syrup.
The grapefruit juice acts on DXM by inhibiting the activity of cytochrome P450 enzymes of the 3A and 1A groups including cytochrome P450 3A4 (CYP3A4). DXM is mostly (up to 90%) O-demethylated into dextrorphan (DXO) by cytochrome P450 2D6 (CYP2D6) and to a lesser extent (10%) N-demethylated into the non-psychoactive metabolite 3-methoxymorphinan (3MM) by CYP3A4. DXO is further metabolized into the inactive metabolite 3-hydroxy-morphinan (3HM). Inhibition of CYP3A4 leads to less DXM being metabolized into 3MM and therefore more DXM being metabolized through the pathway of DXO, leading to higher plasma concentrations and slower degradation of DXO. Therefore, with enough grapefruit juice, the overall trip should be significantly more intense.
Preparation methods for this compound within our tutorial index include:
Toxicity and harm potential
The toxicity and long-term health effects of recreational DXM use in humans has not been studied in any scientific context and the exact toxic dosage is unknown.
Anecdotal evidence suggests that there do not seem to be any negative health effects attributed to simply trying DXM at low to moderate doses by itself and using it sparingly (but nothing can be completely guaranteed). Independent research should always be done to ensure that a combination of two or more substances is safe before consumption.
Despite early speculation that DXM may cause neurotoxicity and Olney's lesions, it has not been shown to cause this effect in animals , However, many chronic users report significant issues with memory, attention, and mood that persist for many months after stopping usage. In rats, oral administration of dextromethorphan did not cause neurotoxic effects in laboratory tests. Oral administration of dextromethorphan repeatedly during adolescence, however, has been shown to impair learning in those rats during adulthood.
It is strongly recommended that one use harm reduction practices when using this substance.
Dependence and abuse potential
As with other dissociatives, DXM produces dependence with chronic use and has moderate abuse potential. When dependence has developed, cravings and withdrawal effects may occur if a person suddenly stops their usage.
A formal survey of dextromethorphan users showed that more than half of users reported experience of the following withdrawal symptoms individually for the first week after long-term/addictive dextromethorphan use: fatigue, apathy, flashbacks, and constipation. Over a quarter reported insomnia, nightmares, inability to feel pleasure, impaired memory, attention deficit and decreased libido. Rarer side effects included panic attacks, impaired learning, tremor, yellowing of the skin, hives and muscle pain. Frequent and long-term usage at very high doses could lead to toxic psychosis and other permanent psychological problems.
Tolerance to many of the effects of DXM develops with prolonged and repeated use. This results in users having to administer increasingly large doses to achieve the same effects. After that, it takes about 3 - 7 days for the tolerance to be reduced to half and 1 - 2 weeks to be back at baseline (in the absence of further consumption). DXM produces cross-tolerance with all dissociatives, meaning that after the consumption of DXM all dissociatives will have a reduced effect. Additionally, some users report an irreversible, permanent tolerance to DXM, which develops over a long period of time and is thought to correlate with the number of doses a person has ingested throughout their lifetime. Some users claim that there is a "50 trip limit", after which the rewarding and unique effects of DXM are said to disappear permanently. The reason for this is unknown, although it may be indicative of neurotoxicity.
Anecdotal evidence suggests that the risk of DXM overdose becomes significant at roughly 15mg/kg to 20mg/kg, or roughly 1000mg - 1500mg in a 70kg person. DXM overdose can have a wide range of effects, including delusions, hallucinations, psychosis, confusion, panic attacks, mania, sedation and severe balance issues, sometimes very inappropriate or violent behavior, increased heart rate, nystagmus and amnesia. The more serious side effects include anesthesia, respiratory depression and risk of accidental injury or self-harm. One should not disrupt a person undergoing this experience as their delusions may cause them to respond with violence. Care should be taken as to not let the user get injured, and medical attention should be sought to prevent severe respiratory depression and choking. Death from DXM toxicity is rare.
Although many psychoactive substances are safe to use on their own, they can become dangerous or even life-threatening when taken with other substances. The list below contains some potentially dangerous combinations, but may not include all of them. Certain combinations may be safe in low doses but still increase the possibility of injury of death. Independent research should always be conducted to ensure that a combination of two or more substances is safe before consumption.
- Stimulants - Combining stimulants with DXM is very dangerous and elevates the risk of high blood pressure problems, strokes, and brain hemorrhages.
- Depressants - Because both depress the respiratory system, this combination can result in an increased risk of suddenly falling unconscious, vomiting and choking to death from the resulting suffocation. If nausea or vomiting occurs, users should attempt to fall asleep in the recovery position or have a friend move them into it.
Serotonin syndrome risk
Combinations with the following substances can cause dangerously high serotonin levels. Serotonin syndrome requires immediate medical attention and can be fatal if left untreated.
- MAOIs such as syrian rue, banisteriopsis caapi, 2C-T-7, αMT, phenelzine, selegiline, and moclobemide
- Serotonin releasers such as MDMA, 4-FA, methamphetamine, methylone and αMT
- Selective serotonin re-uptake inhibitors (SSRIs)
- Serotonin-norepinephrine reuptake inhibitors (SNRIs) such as tramadol and DXM
- Modafinil induces the CYP3A4 enzyme that DXM, and its metabolite DXO, are metabolized by.
- DXM has been shown to prevent and reverse morphine tolerance while also increasing analgesic effects as well as potentiating the analgesic activity of NSAIDs, naproxen, piroxicam, etodolac, diclofenac, and ketorolac.
DXM is available either over the counter or by prescription in most countries. Some countries require the purchaser to be over 16, 18 or 21. It is available for legal purchase in a variety of forms online.
- Austria: Dextromethorphan is not listed in the "Suchtmittelgesetz" (Federal Law on Narcotics). Sales of DXM containing medications are restricted to pharmacies. DXM containing preparations are available at pharmacies without a prescription.
- Canada: Dextromethorphan is listed as specifically exempt from the Controlled Drugs and Substances Act. It is available OTC in Canada and can legally be obtained in powder form.
- Germany: Dextromethorphan is not listed in the "Betäubungsmittelgesetz" (Federal Law on Narcotics). Sales of DXM containing medications are restricted to pharmacies. DXM containing preparations are available at pharmacies without a prescription.
- Mexico: Dextromethorphan is not listed in the General Health Law (Ley General de Salud), which specifies which substances represent a risk to public health. It is also listed in the Reference Medicine Listing as a General Health Law article 226 fraction VI drug, which means it can be freely sold even in businesses that are not legally registered as pharmacies. In practice, this translates into DXM-only syrups being available off-the-shelf and without prescription at any supermarket with a pharmacy section.
- Russia: Dextromethorphan is a schedule III controlled substance.
- Switzerland: Dextromethorphan is listed as a "Abgabekategorie C" pharmaceutical, which is sold exclusively in pharmacies without a prescription but needs approval of a medicinal.
- Dicpinigaitis, P. V., Morice, A. H., Birring, S. S., McGarvey, L., Smith, J. A., Canning, B. J., & Page, C. P. (2014). Antitussive drugs—past, present, and future. Pharmacological Reviews, 66(2), 468-512.
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- Oral administration of dextromethorphan does not produce neuronal vacuolation in the rat brain (PubMed.gov / NCBI) | http://www.ncbi.nlm.nih.gov/pubmed/17573115
- Impairments in water maze learning of aged rats that received dextromethorphan repeatedly during adolescent period | http://en.wikipedia.org/wiki/Recreational_use_of_dextromethorphan#Risks_associated_with_use
- Side effects of dextromethorphan abuse, a case series (PubMed.gov / NCBI) | http://www.ncbi.nlm.nih.gov/pubmed/16122622
- Center for Substance Abuse Research - DXM | http://www.cesar.umd.edu/cesar/drugs/dxm.asp
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- Clinical pharmacokinetic profile of modafinil. (PubMed.gov / NCBI) | http://www.ncbi.nlm.nih.gov/pubmed/12537513
- Dextromethorphan attenuates and reverses analgesic tolerance to morphine. (PubMed.gov / NCBI) | http://www.ncbi.nlm.nih.gov/pubmed/7708410
- Oral administration of dextromethorphan prevents the development of morphine tolerance and dependence in rats. (PubMed.gov / NCBI) | http://www.ncbi.nlm.nih.gov/pubmed/8951930
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