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This section covers general information about dextromethorphan, herein referred to as DXM. IUPAC chemical names are in a sans serif font, in square brackets. Note the following abbreviations:

CNSCentral Nervous System (brain and spinal cord)
CYACover Your Ass. Remember this one!
OTCOver The Counter (i.e., non-prescription)
PCP[1-(1-phenylcyclohexyl)piperidine] (phencyclidine, "angel dust", etc.)

PLEASE NOTE that the UK (and European?) name of acetaminophen is paracetamol. They refer to the same substance.

If you get nothing else out of this FAQ, let it be this: Remember that the use of DXM is, in general, safe, but please remember the following basic guidelines:
* Do not use DXM on a constant or frequent basis! Like alcohol, constant or frequent (more than once or twice a week) use may be dangerous.
* Do not use DXM if you have a history of: mental illness, seizures, epilepsy, liver or kidney disorders, or hypertension.
* Do not use DXM if you are pregnant or nursing. Dissociatives affect fetal development.
* Never use a product containing acetaminophen/paracetamol (Tylenol™). Large doses of acetaminophen/paracetamol can cause liver damage or death.
* Never take DXM if you are taking, will take, or have taken within the past two weeks, a monoamine oxidase inhibitor (MAOI). MAOIs include harmine, harmaline, and some prescription drugs for depression and Parkinson's disease.
* Never take DXM if you are taking, will take, or have taken within six weeks, the prescription antihistamine terfenadine (Seldane™), or any other prescription, non-drowsy antihistamine (e.g., Claritin™ or Hisminal™).
* Don't start out with a high dose, or rush in to higher dosage levels. Instead, gradually increase from your last experiences. DXM can be very different at different dosage levels.
* Never experiment with hallucinogens without a sober person around to help you in case you get into trouble.
* NEVER, EVER, EVER drive under the influence of any intoxicating drug including DXM!
* Avoid all products containing DXM and other active ingredients.
* Avoid the following DXM-only products, which when taken at recreational doses cause unpleasant effects: Benylin DM
* Remember that DXM can sometimes trigger panic attacks in susceptible individuals, especially those inexperienced with DXM. This is a major cause (if not the major cause) of tachycardia (high heart rate) from DXM. All the more reason not to rush in to anything.
* Always remember: recreational use of DXM is still a great unknown. The brain you are risking is your own.

2.1 DXM Quick Reference Page

Dextromethorphan (decks-tro-meth-OR-fan), or DXM, is a cough suppressant found in over-the-counter medications. It has also been used recreationally for at least 30 years, without much harm or publicity. Although chemically related to opiates, its effects are closest to ketamine's. In addition to suppressing coughs, DXM is used medically for diagnostic purposes, and may be useful for a variety of conditions from seizures to heroin addiction. In the brain, DXM blocks the dopamine reuptake site, activates the sigma receptor, and blocks the open NMDA channel. (None of these effects are permanent).

Occasional recreational use of DXM is probably safe, though side effects and risks have been noted (I hereby tell you not to use any recreational drug including DXM). Many cough medicines contain ingredients other than DXM; some, like acetaminophen (paracetamol) can be fatal when an overdose is taken. The commercial preparations which can be used recreationally are those containing DXM only In the USA this includes mostly Vicks Formula 44™, Robitussin Maximum Strength Cough™, Drixoral Cough Liquid Caps™, and generic equivalents. All should list ONLY dextromethorphan hydrobromide under active ingredients. Avoid Benylin DM™. The above cough syrups have 3mg/ml (15mg per teaspoon), for 360mg per 4oz bottle and 720mg per 8oz bottle; the cough gelcaps have 30mg each. Preparations like Robitussin DM™ which contain guaifenesin may cause vomiting.

Never take DXM with, or up to two weeks before or six weeks after, the prescription "non-drowsy" antihistamines (allergy medications) Seldane™, Claritin™, or Hisminal™. Never take DXM with, or up to two weeks before or three weeks after, a MAOI (Monoamine Oxidase Inhibitor) - certain drugs for depression; you will probably be told by your doctor if your drug is a MAOI (Prozac™ isn't). Never drive under the influence of DXM. Don't take DXM more than once or twice a week. Don't take DXM if you have a history of mental illness, panic attacks, seizures, liver or kidney disease. Some people react very badly to DXM; others don't experience anything at all, partly from inherited lack of an enzyme. Prozac™ blocks this enzyme and may lengthen or change the DXM trip. Recreational DXM use may be illegal. DXM may cause false positives on drug tests.

DXM trips vary depending on dosage, and can be lumped into four very different plateaus, or types of trips, depending on the amount taken. Dosages are given in milligrams per kilogram, so multiply the figure by your mass in kg (or pounds divided by 2.2). The first plateau, 1.5 to 2.5 mg/kg, is like a slightly intoxicating stimulant; music and movement are often pleasurable. The second plateau, 2.5 to 7.5 mg/kg, is intoxicating, with a "stoning" a bit like that of nitrous oxide or marijuana; sounds and sights seem to be on strobe-effect ("flanging"), short-term memory is somewhat disrupted, and there are occasional mild hallucinations. The third plateau, at 7.5 to 15mg/kg, consists of strong intoxication, hallucinations, and overall disturbances in thinking, senses, and memory; third plateau trips can be unpleasant. The fourth plateau, above 15mg/kg, is similar to a sub-anesthetic dose of ketamine, with dissociation of the mind from the body, and may be dangerous physically and psychologically. Most recreational use of DXM happens at the first and second plateau. DXM starts to become toxic around 20 to 30mg/kg.

While occasional recreational use of DXM is probably safe, some people react very badly to dissociatives, especially at high doses, and may panic. Frequent DXM use, like frequent alcohol use, may be dangerous and should be avoided. Please be safe, be sensible, and use your brain; it's the only one you'll ever have.

From The Dextromethorphan FAQ: Answers to Frequently Asked Questions about DXM, v3.0, by William White ( Available on Usenet rec.drugs.psychedelic and on the World Wide Web via This section may be freely printed or photocopied separately provided it is kept intact, on one page.

2.2 What is Dextromethorphan (DXM) Hydrobromide

Dextromethorphan hydrobromide is the water-soluble salt of dextromethorphan (DXM) and hydrobromic acid. DXM is a synthetic morphine analog, similar to levorphanol. DXM has been in use in the USA for approximately 30 years, and has replaced codeine as an OTC cough suppressant . It has no traditional opiate-like activity, and is not a substitute for codeine as an analgesic (1-3).

DXM has been popular as an "underground" recreational drug for at least 30 years (3). It is probably one of the few OTC medicines with any serious recreational use potential (ephedrine might also qualify). It is both extremely safe and very effective as a cough suppressant.

DXM's IUPAC name is [(+)-cis-1,3,4,9,10,10a-hexahydro-6-methoxy- 11-methyl-2H-10,4a-iminoethanophenanthrene], and is also (and more commonly) known as 3-methoxy-17-methyl-(9alpha,13alpha,14alpha)-morphinan; CAS-125-71-3 (1). Note: the 3-methoxy and 6-methyl groups are pointed out for later notes.

(Oh, just as a side note, I'm proud to say that for once I actually got the IUPAC name right all by myself - the Merck Index lists the same thing).

The recreational use potential of DXM has not, in general, been well known, either by drug users or by physicians. Not too long ago, many physicians denied that dextromethorphan was psychoactive at all; whether this was out of ignorance or a desire to prevent recreational use, I do not know (probably the latter). At present, there is an increasing body of knowledge about DXM's potential for recreational use (and abuse) available in medical journals (3-7, 133, 137, 142-144).

DXM is unique among recreational drugs for several reasons. First, it is pharmacologically unlike most other recreational drugs (PCP and ketamine being its nearest relatives). Second, its effects can vary considerably from individual to individual. Finally, it can cause quite different effects at different dosage levels, ranging from mild euphoria to full dissociation.

2.3 What is Dextromethorphan Polistirex?

Dextromethorphan Polistirex is a time-release formulation of DXM; the "polistirex" refers to a sulfonated styrene-divinylbenzene copolymer complex (1-2). It is occasionally spelled polystirex or polystyrex. Unlike the HBr salt, which is absorbed fairly quickly, this compound is intended for longer duration cough suppression. Most, but not all, people who use DXM recreationally tend to prefer the HBr form (which is also much more readily available). The polistirex preparation will probably increase the ratio of DXM to DXO (see next section).

Dextromethorphan polistirex may be more toxic than the hydrobromide version, possibly due to buildup of DXM in the bloodstream (146).

2.4 What is Dextrorphan

Dextrorphan is a metabolite of DXM (i.e., the body converts DXM to dextrorphan). The conversion from DXM to DXO occurs via removal of the methyl group at position 6, a process called "O-demethylation". DXO is very similar chemically to DXM, and reacts with the same receptors in the body, but with a very different spectrum. Whereas DXM is strongest at the PCP2 and sigma receptors, DXO primarily targets the NMDA receptor (see Chapter 6). The practical upshot is that the dissociative and intoxicating or "stoning" effects are stronger with DXO, whereas the stimulation, cognitive alterations, and psychotomimetic (literally, "psychosis-like") effects are stronger with DXM. Most DXM users find some balance between the two to be the most pleasurable. Too much sigma activity is usually regarded as unpleasantly dysphoric and disturbing, and if prolonged, may be dangerous (102, 136).

Fortunately, you don't have to worry about converting DXM to DXO; the body does it for you via an enzyme called P450-2D6 (debrisoquine 4-hydroxylase). However, between 5 to 10% of the Caucasian population lacks this enzyme (12-15), and in the rest of us it can vary. Many drugs can temporarily block P450-2D6 from working (10-11) and thus alter the balance between DXM and DXO. For a list of these drugs, see Appendix 1.

One of DXM's metabolites, 3-methoxymorphinan, can itself block P450-2D6. As a consequence, taking a second dose some time after the first dose of DXM will probably increase the ratio of DXM to DXO in the bloodstream. Taking the dose all at once, on the other hand, will probably increase the relative amount of DXO. Generally, then, the quicker the dosing, the more DXO and less DXM, and the more NMDA blockade (like ketamine) and the less sigma and PCP2 activity. Subcutaneous injection leads to very little conversion from DXM to DXO.

When discussing effects, this text often uses "DXM" to refer to both dextromethorphan and its metabolite, DXO.

2.5 How does one obtain and use DXM?

DXM is available at drugstores throughout the world; generally it is not available on the street (I wouldn't trust anyone saying he or she had street DXM; it's probably ketamine, PCP, or something totally unrelated). It is most commonly available in cough syrups, though some syrups contain other ingredients which can make you sick (or dead) if you take too much of them. It is also available in gelcaps and in some places in capsules.

DXM can also be extracted from cough medicines, and the extract can be taken orally, injected subcutaneously, intraperitoneally, intramuscuarly, or intravenously. It can probably also be snorted or used rectally (though why one would want to I don't know). Smoking doesn't seem very effective.

Some drugstores keep track of people who frequently buy DXM-containing cough preparations, especially if they buy multiple bottles at once or tend not to buy other things at the same time. This is less common in larger supermarket/drug stores. In some cities where DXM use has become popular (and come to public attention), sales have been restricted to adults. In Utah in the 1980's, DXM was placed behind the counter due to recreational use.

Drinking Cough Syrup

DXM is widely available in cough syrups, both brand-name (such as Robitussin™ or Vicks Formula 44™) and store brands. Most DXM-containing cough syrups also contain one or more of the following other active ingredients: nasal decongestants, antihistamines, acetaminophen, or guaifenesin (see Section 2.7). As a rule, you want to avoid all of them.

Generally speaking, DXM cough syrups all taste nasty. This is for two reasons: to cover up the (even nastier) taste of DXM itself, and to prevent recreational use. The generics tend to be less thick, and thus more drinkable, than the brand names. Some people prefer to mix the DXM with sodas; others find this only makes an already unpleasant task even more unpleasant. Your Mileage May Vary.

Most people who have used DXM cough syrups recreationally seem to prefer to take it on a mostly empty stomach, possibly with crackers or some other source of carbohydrates. I generally feel that you should avoid slamming your kidneys and pancreas with a lot of glucose at once; thus I think some crackers or chips beforehand would be advisable. Greasy food should be avoided both before and after taking DXM. Most people report that if carbonated drinks are ingested, they should be clear (e.g., 7-Up™).

Gelcaps and Capsules

There are "gelcaps" (liquid or gel filled capsules) available that contain DXM, but they tend to be brand-name only. One brand containing only DXM is Drixoral Cough Liquid Caps™. They come in boxes of 10 or 20 gel capsules, each containing 30mg of DXM. The gel capsule itself is red colored; the liquid inside is actually clear (and tastes very, very bad). The capsules are somewhat large, and difficult if not impossible to take without liquid to wash them down. This brand also comes with a $0.50 or $1.00 manufacturer's coupon inside, which some have taken to calling Drixoral™ Dollars (after Camel Bucks™, a fake currency coupon in Camel™ cigarettes which could be collected and "spent" on various stuff). Note that Drixoral also makes several other liquid and capsule products, all of which contain undesirable active ingredients besides DXM.

Absorption from the gelcaps takes some time, and can be sped up by cracking open each gelcap in your mouth before it is swallowed. Note, however, that the liquid inside is apt to spurt out, and it tastes bad. Really, really bad - sour and bitter and cloying all at once with a stickiness that won't go away. However, if you can stand it, you can become used to it after the first few gelcaps. You can also crack open the gelcaps and try to collect the liquid, but it tends to go everywhere.

Contac CoughCaps™ are available in Canada, and are capsule formulations of DXM. I have not personally seen them. In several countries, there are over-the-counter tablet or capsule DXM pills containing 30mg per tablet/capsule; one example is Romilar™. Thus far I know they are available in some areas of southeast Asia and in Saudi Arabia.

Pharmaceutical and Chemical Suppliers

DXM is not scheduled in the USA (or most other parts of the world), and consequently should be available via pharmaceutical chemical suppliers. For example, Sigma Chemical Company (1-800-325-3010) lists DXM hydrobromide (product D2531) for US $18.20 for 5 grams, US $128.45 for 50 grams. Note that I have no affiliation with Sigma in any way; I just happened to have a copy of their catalog handy when writing this.

In theory, it would be fantastically cheap and easy to order DXM this way; in practice, it's possibly difficult, and probably a Very Bad Idea. First off, most chemical companies are wary about selling to individuals (and if you're not a legal adult, forget it). Secondly, there's a significant chance that your order will be reported to the DEA, and although it's not technically illegal, if enough people do this, that may change very quickly.

Still, though, if you have the courage or stupidity to try, there's no reason why this shouldn't be a reasonable source. Just use your head. And don't mention the FAQ.

Extracted DXM Ingestion

DXM can be extracted (see Section 7.1 and 7.2) and the extracted DXM can be taken orally, either as free base or as salt (the free base should convert to the hydrochloride salt in your stomach). The salt usually available is hydrobromide, but I see no reason why hydrochloride, or even acetate or citrate, cannot be used. The free base tends to be somewhat alkaline and should be avoided unless combined with food and/or juice (or other acidic beverage). When taken on a mostly empty stomach, the extract is generally absorbed faster than cough syrups, gelcaps, or capsules. Some extraction processes may convert some or all of the DXM into dextrorphan (DXO). Extracted DXM, unlike cough syrups and gelcaps, has no bromide toxicity (see Section 2.7).

Injection and Other Routes

DXM hydrobromide is soluble in saline, and I see no reason why other acid salts shouldn't be - though their long-term stability may be doubtful. However, injection is a very dangerous route, especially if the substance in question is not prepared specifically to be injected. Some of the potential risks include: sterile abscesses, torn or collapsed veins, bruising, muscle fiber damage, histamine release, infection (hepatitis B, HIV, etc.), embolism (and possible resulting stroke or cardiac arrest), increased chance of addiction, overdose, and people mistaking you for a junky. True, most of these are unlikely, and if done correctly injection is generally very safe. However, the key word is correctly. If you're still interested, consult a medical text; I'm not going to teach you how to shoot up.

A few notes for those brave or stupid enough to still be interested. Intravenous (IV) and intramuscular (IM) injection both seem to produce similar results in animals, and IM injection is almost always safer. DXM can also be injected intraperitoneally (IP), but that evidently requires some skill. Subcutaneous (SC) injection ("skin popping") leads to slower absorption and a great increase in the amount of DXM relative to DXO. All injected drugs should be completely pure, dissolved in the appropriate physiological saline. In the case of SC (and possibly IM) injection, injecting too large a volume of material can lead to a sterile abscess.

DXM can also theoretically be snorted although I don't generally think this is a very smart route; the nasal lining is very tender. DXM free base is probably too alkaline to try this with. It can also probably be used rectally, but somehow the thought of a cough syrup enema doesn't thrill me.

Smoking DXM free base has been attempted several times by various people without success. It seems that some of the DXM is destroyed by the heat, and the remaining DXM is extremely harsh on the lungs. Too bad, really, since self-titration is usually easiest with smoking.

2.6 What are some typical DXM-containing commercial preparations?

Rather than listing the content of commercial DXM preparations (I gave up since there are so many!), I have decided to list brands and generic equivalents which contain only DXM. All expressions are in metric. 1tsp is approx. 5ml; a 4oz bottle is approx. 120ml, and an 8oz bottle approx. 240ml. All preparations listed contain no other active ingredients besides DXM.

1mg/ml DXM (120mg per 4oz bottle)

1.5mg/ml DXM (180mg per 4oz bottle)

2mg/ml DXM (240mg per 4oz bottle)

3mg/ml DXM (360mg per 4oz bottle)

15mg/capsule or tablet

30mg/capsule or tablet

2.7 What should I know about other drug ingredients?

There are five main classes of active ingredients that are present in OTC DXM-containing products: decongestants, antihistamines, guaifenesin, analgesics, and alcohol. Each will be discussed in turn, followed by "inactive" ingredients. With the exception of alcohol, all should be avoided, although for differing reasons. Additionally, some of the dyes and other "inactive" ingredients may cause some people trouble.


There are three nasal decongestants that are used in OTC cough formulas in the USA: PPA, pseudoephedrine, and phenyleprine (the latter is almost always found with antihistamines). PPA is also known as phenylpropanolamine (from which the acronym PPA is derived), norephedrine, and the IUPAC name [alpha-(1-aminoethyl)benzyl alcohol]. Pseudoephedrine, known as the brand name Sudafed™, has the IUPAC name [(+)alpha-(1-methylamino)benzyl alcohol]. Phenyleprine is [(-)-3-hydroxy-alpha-(methylaminomethyl)benzyl alcohol] (1-2).

These decongestants belong to a class of chemicals known as the phenethylamines; this class also includes methamphetamine, MDMA (ecstasy), MDA, etc., and tend to be DEA scheduled. Decongestants are not scheduled by the DEA (this is USA laws) because they do not have significant psychostimulant activity. Ephedrine, which is similar to pseudoephedrine, and is (or was, depending on your state) available throughout truck stops and mail-order pharmaceutical companies in the USA, does have mild stimulant properties; thus its popularity as a form of "legal speed". All of these drugs stimulate the sympathetic nervous system (the "fight or flight" system) and are thus called sympathomimetics.

What nasal decongestants do share with the more potent amphetamines is the peripheral activity common to sympathomimetics, such as vasoconstriction (constriction of blood vessels) and decreased nasal secretions (the good side), and - with larger doses - insomnia, hypertension, heart rhythm abnormalities, hemorrhaging, stroke, or death (the bad side) (8). Note that these are extreme reactions, and that individual tolerance to sympathomimetics tends to vary considerably. Tolerance can build quickly, and a fatal dose for one person may have only a mild effect on another person.

Because of the potential danger of hypertension, exceeding the recommended dose of DXM and decongestant containing preparations may be asking for trouble. Most people can probably handle it in smaller recreational doses, but the peripheral "speediness" can be distinctly unpleasant. Anyone with high blood pressure or the like has no business taking large quantities of decongestants. Try to avoid these drugs.


The antihistamines operate by blocking histamine receptors (see Section 6 for an explanation of receptors). Peripherally, this has the effect of reducing the symptoms of histamine activity (stuffy and runny nose, itchy eyes, hives, rashes, etc.) associated with infections and allergies. In the CNS, histamine is partially responsible for wakefulness, and antihistamines that cross the blood-brain barrier will cause sleepiness. In fact, most OTC "sleeping pills" in the USA are really just antihistamines (although melatonin is making inroads as an alternative). There are antihistamines that do not cross the blood-brain barrier (e.g., Seldane™) but these are prescription in the USA.

High doses of antihistamines can result in dizziness, impairment of concentration, extreme sedation (or, paradoxically, insomnia), headache, heart palpitations, dry mouth, gastric discomfort, delusions, and abnormally high blood pressure. Doses of 30-60mg/kg have been fatal in very young children; most adults, however, are very unlikely to overdose on antihistamines. Death, when it does occur, is from cardiovascular collapse or respiratory arrest (8). High doses of prescription antihistamines are much more dangerous; do not mix DXM with prescription antihistamines!

The danger of an antihistamine overdose is very low when using a DXM-containing product recreationally. However, you will most likely experience some unpleasant symptoms, such as sleepiness, dry mouth, heart palpitations, etc. For this reason, I recommend against products containing antihistamines.


Guaifenesin (gwye-FEN-a-sin) [3-(2-methoxyphenoxy)-1,2-propanediol] is an expectorant; it increases the production of respiratory tract fluids, thus making phlegm less viscous and easier to cough up. Guaifenesin has been shown effective as an expectorant, but is of no use as a cough suppressant. It is often combined with dextromethorphan. Guaifenesin should not be used for chronic coughs or coughs accompanied by excessive phlegm (1-2).

High doses of guaifenesin tend to induce emesis (i.e., you puke). Other effects from high guaifenesin doses are not well known, but probably not serious. However, as most people do not enjoy vomiting, I would recommend avoiding guaifenesin-containing products.


Acetaminophen (called paracetamol in the UK) is the most common analgesic (painkiller) present in cough suppressant formulas. It is closely related to the NSAIDs (non-steroidal anti-inflammatory drugs) of which aspirin and ibuprofen are the two most common examples. Unlike the OTC NSAIDs, however, acetaminophen/paracetamol does not tend to irritate the stomach, and thus its inclusion in cough syrups.

An acetaminophen overdose is very dangerous. Normally, acetaminophen is metabolized (broken down) in the body by two separate pathways, both of which lead to harmless metabolites. However, these two pathways can only metabolize so much before saturating. At that point, the remaining acetaminophen is metabolized by a cytochrome P450 liver enzyme. The metabolite via the P450 pathway is toxic to the liver (2, 8).

Furthermore, this doesn't happen right away; it can take 16 hours before any signs of liver damage show up. This delayed toxic effect has been responsible for the rather painful deaths of some people who (accidentally or not) overdose on acetaminophen, and then think they are fine when no immediate problems occur. There is an antidote (acetylcystine), but it must be administered within the first 12 to 16 hours.

The toxic dose of acetaminophen can be as low as 50mg/kg; for a 60kg person this is only six acetaminophen tablets. This is unlikely but possible. DO NOT UNDER ANY CIRCUMSTANCES USE RECREATIONALLY ANY DXM PRODUCT WHICH ALSO CONTAINS ACETAMINOPHEN / PARACETAMOL!

As for aspirin and ibuprofen, the other two most common OTC painkillers, both tend to irritate the stomach at high doses. I recommend against them, especially if you have an irritable stomach. Never take large doses of aspirin or ibuprofen if you have an ulcer.


Most cough syrups contain some alcohol, to act as a carrier and to numb the throat. With a few exceptions (such as Nyquil™), the amount of alcohol is not usually very great. While alcohol does not, in general, mix well with DXM as a recreational drug, the amount in cough syrups should not cause trouble unless you are specifically sensitive to, or attempting to avoid, alcohol. There are alcohol-free preparations available; many gelcaps are alcohol-free.

Food Coloring / Dyes

Some of the dyes used in cough formulas may give some people allergic reactions. Most notable among these is tartrazine (FD&C Yellow #5). Generally, these dyes are not a problem unless you take a lot of them (which recreational DXM use may involve). If you think you may be allergic to a dye, switch to a different brand (or more accurately, a different color). It is also a good idea to keep an antihistamine (not a prescription or non-drowsy one!) nearby in case an allergic reaction does occur.

Bromide Ions

DXM is usually ingested as a hydrobromide salt. Large amounts of bromide ions can cause sedation and eventually lead to bromism (bromide poisoning), which affects (among other things) the skin and nervous system. I don't think this is terribly relevant for users of DXM (recreational or not); however it is one more reason to avoid prolonged high-dose use. You can avoid bromide ions by converting the DXM to free base and/or hydrochloride salt (see Section 7.6). Some physicians do believe that prolonged heavy use of DXM may lead to bromism (147).

Other "Inactive" Ingredients

Cough syrups tend to contain several thickening and sweetening agents. Glucose, sucrose, invert sugar, and fructose are all commonly used as sweetening agents. Obviously, a person with blood sugar problems (diabetes or hypoglycemia) should not take large amounts of these syrups.

Thickening agents are not usually a problem. Occasionally people will look on cough syrup labels and see propylene glycol or polyethylene glycol, and (thinking about ethylene glycol, i.e., antifreeze) worry about toxicity. Propylene glycol (a thickening and emulsifying agent) is not toxic, even though ethylene glycol is. The same goes for polyethylene glycol (PEG) - it's also nontoxic. About the worst you will get from any of these is an upset stomach.

One general note - keep in mind that your body does eventually have to use or excrete whatever you eat and drink. Drinking huge amounts of sugars and thickening agents can put a fair amount of load on the kidneys and should definitely be avoided if you have kidney problems already. There is anecdotal evidence that regular high-dose use of DXM cough syrups (without eating much) has led to kidney damage due to the glucose load. I cannot confirm this but I can't disprove it either.

2.8 Why are so many DXM preparations in liquid form?

Cough preparations are in liquid form for two reasons. First and foremost, most people have the (mistaken) belief that in order for a cough suppressant formula to work, it must coat the throat. This is complete bunk. If consumers were a bit smarter, we wouldn't have to gag down cough syrup. There are, in fact, gel-capsule cough suppressants on the market, and I expect that tablet or capsule dextromethorphan will eventually be common. Second, tablet-form DXM preparations have been kept from the market in an attempt to prevent their recreational use.

2.9 Is recreational use of DXM illegal?

Possibly. There may be laws making it a crime to use OTC medicines in any way other than directed on the label. Not that this stops people from using ephedrine (a bronchodilator) as a stimulant. Nor are you likely to get caught and/or prosecuted; the authorities are much too busy infringing upon our civil rights looking for the illegal drugs. But, remember - I SPECIFICALLY instruct you NOT to use any medicine in a manner inconsistent with its labeling.

Furthermore, suggesting to someone that they use DXM as a recreational drug could also be violating a law - against prescribing drugs as a layperson. Again, it's not likely to happen, but it is possible.

DXM is a prescription drug in Sweden (9). It is prescription and scheduled in western Australia unless combined with other active ingredients. It may become prescription in other countries. In drug stores in some areas it is kept behind the counter, and must be requested.

2.10 Other (medical) uses for DXM


Dextromethorphan is commonly used to determine cytochrome P450-2D6 activity (10-11). Cytochrome P450-2D6, or debrisoquine 4-hydroxylase, is a liver enzyme which converts DXM into dextrorphan, and is extensively involved in the metabolism of other drugs. About 5-10% of Caucasians and 0.5% of Asians seem to lack P450-2D6 entirely (12-15); in the remaining individuals, its activity can vary significantly due to minor genetic variance (15-18). Between 0.5% and 2% of the population has multiple copies of the P450-2D6 gene, leading to extremely high activity (158). By looking at the metabolites of DXM, a physician can determine P450-2D6 efficiency, and adjust drug dosage to match.

One area in which DXM (as well as other NMDA blockers; see Section 6.3) shows great promise is in the prevention of brain damage resulting from excitotoxicity (over-stimulation of nerve cells to the point of cell death) and other types of nerve cell damage (19). DXM may reduce or eliminate the brain damage resulting from conditions such as fever, hypoxia (lack of oxygen) (20), ischemia (cutoff of blood to brain cells) (21-22), physical injury (23), infection (such as poliomyelitis, encephalitis, and meningitis), stroke, seizure, drug toxicity (24-25), and withdrawal from long-term dependence upon certain drugs (notably alcohol, barbiturates, and benzodiazepines such as Valium™) (26-29).

In the case of infection (and in particular poliomyelitis), it has been demonstrated that the damage to the CNS often occurs not from the infection, but from the body's own defenses, and notably from a chemical called quinolinic acid (a metabolite of tryptophan) (30, 31). Quinolinic acid is a very potent agonist (activator) at excitatory amino acid receptors, of which NMDA is one type; DXM prevents quinolinic acid from activating NMDA receptors. (Incidentally, the function of quinolinic acid - if it has any - is not currently known; it may be involved in the immune response).

As for physical trauma, hypoxia, seizure, stroke, etc., there are several experiments which indicate that the majority of the damage again comes from excitotoxicity at excitatory amino acid receptors. While DXM has shown somewhat less success there (possibly due to other factors being involved), it still has potential.

DXM is currently being evaluated as an anticonvulsant (32, 33). The animal data are somewhat conflicting, but the most accurate model of epileptic seizures (called kindling) responds well to DXM. Preliminary studies in humans indicates that even very low levels of DXM may help prevent seizures. This effect is not, as was originally thought, due to NMDA receptors; instead, it is probably due to sigma receptors or voltage-gated ion channels (32). Interestingly, DXM produces different side-effects in kindled (seizure-susceptible) animals than in non-kindled animals (this may be due to uncoupling of NMDA receptors). It is possible that humans susceptible to seizure may experience different effects from recreational DXM use.

Another new area where DXM has potential is in combating the withdrawal symptoms of opiate addiction. DXM plus diazepam (Valium™) was more effective at combating the symptoms of heroin withdrawal (goose flesh, tremors, dilated pupils, joint ache, etc.) than chlorpromazine (Thorazine™) plus diazepam (34). This is most likely due to DXM's ability to block NMDA receptors. A further study (134) verified this, and found that adding tizanidine (an alpha-2 adrenergic agonist) to DXM was better yet.

DXM has shown some potential for treating some of the problems associated with mental retardation (35). It may also be of use in treating Parkinson's disease (36) and ALS (Lou Gehrig's Disease) (171). DXM may be useful in conjunction with opiates for alleviation of both acute and chronic pain (37) and may reverse opiate tolerance (172). It may even be useful in fighting lung cancer (38).

2.11 Drug Interactions

DXM should not be used (either recreationally or at normal dosage levels) by people who are taking a monoamine oxidase inhibitor (MAOI, rhymes with "wowee") - either a prescription MAOI or a recreational one such as harmaline. Note that there is considerable confusion among drug users about what is and isn't a MAOI. MAOIs include a few drugs prescribed for depression and Parkinson's disease, and a few rare recreational drugs derived from exotic plant sources (harmine and harmaline, from Syrian Rue and Yagé, for example). Prozac™, MDMA, cheese, beer, Seldane™, etc., are not MAOIs - they are things to avoid when taking a MAOI. If you are taking a prescription MAOI you will almost certainly know, as your physician will have (hopefully!) told you to avoid eating aged cheeses. Combining DXM and a MAOI has been fatal (3).

Fluoxetine (Prozac™) is a cytochrome P450-2D6 inhibitor (39), and will change the characteristics of a DXM trip somewhat (increasing the ratio of DXM to DXO). Other P450-2D6 inhibiting drugs will probably do the same; see Appendix 1. The duration of the trip may be greatly extended by P450-2D6 inhibitors; some users have reported effects lasting 12 to 24 hours past the normal duration. The potency of DXM may also be enhanced via other mechanisms by fluoxetine (40).

DXM should not be taken (recreationally or at normal dosage levels) with the prescription antihistamine terfenadine (Seldane™). This combination has been fatal (41). Terfenadine has been implicated in other drug interactions, incidentally. The reason for this interaction seems to be that terfenadine, which is normally metabolized by a P450 enzyme, induces heart irregularities when it builds up. DXM may saturate the P450 enzymes that normally metabolize terfenadine. Incidentally, this probably applies to Claritin™ and Hismanal™ as well; avoid combining them with DXM.

Like other psychoactive drugs, DXM should not be used by people who are mentally or emotionally unstable. I tend to believe that NO recreational drug (legal or not) should be used unless the user is in a calm, rational mood, free from anxiety or negative emotions, and is in a controlled setting where s/he will not have to drive. Speaking of which, as DXM is an intoxicating drug, don't drive under the influence. Ever. But I shouldn't have to tell you that, right?

High doses of DXM can be very dissociative. While this is not necessarily bad, you should know what you are getting into first. A high-dose DXM trip is not like an LSD trip; it more closely resembles ketamine. You will most likely encounter experiences that you didn't expect, and possibly didn't want. While this is OK for the more committed psychonaut, casual users of hallucinogens might want to think twice before taking a high dose.

Prolonged use of DXM, or extended doses of DXM (including the polistirex formulation), may cause problems due to the buildup of DXM (as opposed to DXO), and the resulting activity at sigma receptors (see Section 6). Sigma receptors seem to have a potent modulatory role on neurons, possibly inducing permanent or semi-permanent changes when they are activated for long periods of time (most studies so far indicate over 3 days of high DXM concentrations are required before such changes occur). Furthermore, sigma activity seems to be correlated with delusional thinking, which should probably be avoided, especially in the inexperienced.

Some people are allergic to tartrazine (FD&C Yellow #5), which is present in several cough syrups. Sensitivity to tartrazine is rare, but is frequent in people sensitive to aspirin. Avoid tartrazine if you are, or think you might be, allergic to it or to aspirin. Note that, based on anecdotal evidence, I believe that sensitivity to other dyes may develop from chronic use.

The large amount of glycerine, glucose syrup, and sugars present in cough syrups can give some people problems ranging from stomach ache to sugar shock. Obviously anyone with diabetes or a family history of blood sugar problems should avoid cough syrups.

2.12 What about other cough suppressants

The only other non-narcotic cough suppressant of which I am aware is a drug called noscapine (42). I have little information on it as of yet; look for more soon. Narcotic cough suppressants include primarily codeine, although any opiate can be used for that purpose (in fact, heroin was originally marketed as a cough suppressant). Opiates have an entirely different set of recreational effects than DXM, however, and are not covered here.

2.13 Can DXM be detected on drug tests

As DXM itself, probably not; nobody bothers to look for it. On the other hand, anecdotal evidence indicates that some people will test positive for opiate use after using recreational DXM. Keep this in mind before using DXM if you have to take a drug test. If worse comes to worse, you can always claim you had a bad cold, and ask them to do a test which will discriminate between opiates and DXM. Good luck!

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