DEXTROMETHORPHAN

Dextromethorphan (DXM) is an over-the-counter (OTC) cough suppressant commonly found in cold medications. DXM is often abused in high doses by adolescents to generate euphoria and visual and auditory hallucinations. Illicit use of DXM is referred to on the street as "Robo-tripping" or "skittling." These terms are derived from the most commonly abused products, Robitussin and Coricidin.

DXM is an antitussive found in more than 120 OTC cold medications either alone or in combination with other drugs such as analgesics (e.g. acetaminophen), antihistamines (e.g. chlorpheniramine), decongestants (e.g. pseudo- ephedrine) and/or expectorants (e.g. guaifenesin). The typical antitussive adult dose is 15 or 30 mg taken three to four times daily. The anticoughing effects of DXM persist for 5 to 6 hours after oral administration. When taken as directed, side-effects are rarely observed.

DXM is abused by individuals of all ages but its abuse by teenagers and young adults is of particular concern. This abuse is fueled by DXM’s OTC availability and extensive "how to" abuse information on various web sites. The sale of the powdered form of DXM over the Internet poses additional risks due to the uncertainty of composition and dose.

DXM abusers report a heightened sense of perceptual awareness, altered time perception, and visual hallucinations. The typical clinical presentation of DXM intoxication involves hyperexcitability, lethargy, ataxia, slurred speech, sweating, hypertension, and/or nystagmus. Abuse of combination DXM products also results in health complications from the other active ingredient(s), which include increased blood pressure from pseudoephedrine, potential delayed liver damage from acetaminophen, and central nervous system toxicity, cardiovascular toxicity and anticholinergic toxicity from antihistamines. The use of high doses of DXM in combination with alcohol or other drugs is particularly dangerous and deaths have been reported.

Abusers of DXM describe the following four dose-dependent "plateaus:"

 Chemistry/Pharmacology:

Dextromethorphan (DXM) (d-3-methoxy-N-methyl-morphinan) is the dextro isomer of levomethorphan, a semisynthetic morphine derivative. Although structurally similar to other narcotics, DXM does not act as a mu receptor opioid (e.g. morphine, heroin). DXM and its metabolite, dextrorphan, act as potent blockers of the N-methyl -d-aspartate (NMDA) receptor. At high doses, the pharmacology of DXM is similar to the controlled substances phencyclidine (PCP) and ketamine that also antagonize the NMDA receptor. High doses of DXM produce PCP-like behavioral effects. DXM may cause a false-positive test result with some urine immunoassays for PCP.

Approximately 5-10% of Caucasians are poor DXM metabolizers which increases their risk for overdoses and deaths. DXM should not be taken with antidepressants due to the risk of inducing a life threatening serotonergic syndrome.

The 2006 Monitoring the Future (MTF) showed that 4%, 5%, and 7% of 8^th, 10^th, and 12^th grade students, respectively, reported nonmedical use of DXM during the previous year. This was the first year MTF added DXM to the survey for students.

A 6-year retrospective study from 1999 to 2004 of the California Poison Control System (CPCS) showed a 10-fold increase in the rate of CPCS DXM abuse cases in all ages and a 15-fold increase in the rate of CPCS DXM abuse cases in adolescents. In 2004, CPCS reports 1,382 DXM abuse cases. About 75% of CPCS DXM abuse cases are adolescents (i.e. ages 9-17) with a median age of 16.

DXM abuse has traditionally been with the OTC liquid cough preparations. More recently, abuse of tablet and gel capsule preparations has increased. DXM powder sold over the Internet is also a source of DXM for abuse. DXM is also distributed in illicitly manufactured tablets containing only DXM or mixed with other illicit drugs such as ecstasy and/or methamphetamine.

DXM is neither a controlled substance nor a regulated chemical under the Controlled Substances Act (CSA). The CSA specifically excluded DXM from any of the schedules in 1970 because of a lack of significant opiate-like abuse potential [21 USC 811(g) (2)]. However the CSA provided that DXM could in the future be added to the CSA through the traditional scheduling process if warranted. DEA is currently reviewing DXM for possible control.