Dextromethorphan was first patented as an antitussive under U.S. Patent 2,676,177[1] in 1954. It was the approved by the United States Food and Drug Administration in 1958 as a cough suppressant. It was immediately made available as an over the counter (OTC) medicine under the brand name Romilar. In the mid 1970s, the recreational abilities of dextromethorphan were apparent within the turbulent American counter-culture and Romilar was removed from store shelves.

Following Romilar's withdrawal from the market, companies such as the now-dominant Robitussin and Vicks began to manufacture dextromethorphan-containing cough syrups with an intentionally unpleasant taste when consumed in large quantities, in an attempt to limit abuse.[2]

Although dextromethorphan was intentionally excluded from the Controlled Substances Act of 1970, public officials across the U.S. have threatened to reconsider its status should public abuse warrant it. The U.S. Office of Diversion Control indicates that the "DEA is currently reviewing DXM for possible control."[3]

Main article: Dextromethorphan Chemistry

Dextromethorphan is an optically-active dextrorotary enantiomer of levorphanol, both an opiate and analgesic which plays parent to various other NDMA receptor antagonists. Dextromethorphan's stereoisomer is levomethorphan, also an opioid analgesic, though it has never been clinically developed. As a stable, organic, bicylic comound, dextromethorphan is not soluble in water, however, it will readily dissolve in chloroform. It appears as a white crystalline powder (occasionally with a yellow tinting) when pure. It is most commonly found as monohydrated salt with hydrobromide. Newer, extended-release formulations contain dextromethorphan bonded to a polystyrene sulfonic acid, usually abbreviated as polistirex, which the body's metabolism slowly dissolves.

Main article: DXM Safety

Use of label-prescribed dextromethorphan doses has the ability to produce any of the following symptoms:

• Body rash
• Itching (commonly referred to as RoboItch)
• Nausea and/or vomiting
• Drowsiness
• Blurred vision
• Dizziness
• Fever
• Dilated pupils
• Increase in body heat
• Sweating
• Hypertension
• Shallow respiration
• Diarrhea and/or other gastrointestinal distress
• Urinary retention
  

Recreational doses (those significantly exceeding label-prescribed amounts), in addition to the aforementioned side-effects, can produce a number of additional conditions including:

• Euphoria
• Dysphoria
• Heart palpitations
• Increased heart rate
• Loss of motor function/balance
• Trembling
• Shaking
• Distorted vision
• Temporary blindness
• Loss of coherence
• Detachment from reality
• Short-term memory impairment
• Inability to speak/comprehend speech
• Closed-eye hallucinations
• Auditory hallucinations
• Completely delusional perceptions - including out-of-body experiences, perceived contact with archetypal beings (such as gods, mythical creatures, etc.)
  

It was once suggested that use of dextromethorphan could lead to Olney's Lesions, a serious condition affecting the brain, though this theory was later refuted.

The most commonly used method, DXM is rapidly adsorbed by the gastrointestinal tract and metabolized in the liver by the cytochrome P450 enzymes. DXM is commonly available for oral ingestion in syrup, gelcap or pill form.

Although possible, it is not advised to inject DXM as injecting DXM in rats has led to the formation of Olney's lesions.[4]

Dextromethorphan reacts with oxygen at room temperature, though not at any appreciable rate. However, at 395-397 Kelvin, dextromethorphan hydrobromide's melting point, this changes and dextromethorphan reacts with oxygen to produce some very toxic chemicals.

Free ("freebase") dextromethorphan will also react with oxygen at its melting point. Anyone attempting to smoke dextromethorphan in the presence of oxygen under normal atmospheric conditions will only end up inhaling nasty compounds such as nitric oxide and the organic products of combustion.

This information is easily verified by looking at a Material Safety Data Sheet for this substance. Dextromethorphan reacts rapidly with oxygen at temperatures above 360 Kelvin. It is in everyone's best interest to know that dextromethorphan is not "smokeable".

Insufflating, or snorting DXM is not advised as neither DXM HBr or DXM freebase are very water soluble. Taking DXM in this manner is not only painful, but ineffective as most of it will only be absorbed once it drips down the back of your throat into your stomach.

Dextromethorphan Hydrobromide is formed when DXM is reacted with hydrobromic acid. It is the form of DXM that is most commonly found in cough suppressants and used recreationally.

Dextromethorphan polistirex is another form of DXM that is time-released. The DXM is surrounded by a thick plastic coating which is slowly degraded during digestion, releasing the DXM. This is used in some cough medicines so when some of the DXM has worn off, then some more will kick in. Some people prefer the extended length of the "trips" this form of DXM offers, and some use this form in conjunction with DXM HBr to maintain a lengthy state of intoxication with a very noticeable peak.

Colloquially known as "Agent Lemon," Dextromethorphan Citrate is usually the end product of most extractions from over the counter DXM products. Instead of being bound to a hydrobromide molecule, freebase dextromethorphan is bound to a citric acid molecule, eliminating any risk of brominism from consuming too much bromine, and also allowing better absorption in the stomach.

Dextromethorphan freebase does not have an acid molecule associated with it and is therefore more basic than other forms of DXM. It can be obtained by extraction as well as Theraflu thinstrips cough. DXM freebase is soluble in alcohol and nonpolar solvents such as naphtha. When taking freebase, taking it with an acid such as citric acid may enhance absorption. Dextromethorthphan is converted to Dextromethorphan HCl in the stomach.