Later this month an FDA advisory committee is scheduled to consider whether the agency should require a prescription for Robitussin, NyQuil, and other medications containing dextromethorphan (DXM), a cough suppressant that has dramatic psychoactive effects in large doses (starting around 10 times the normal dose). This week, in anticipation of the meeting, the FDA posted 135 pages of information about DXM, which you can peruse here (PDF). The case for scheduling DXM is weak, but that does not mean it will not happen. Other possibilities include banning sales to minors (a measure supported by the pharmaceutical industry) or putting DXM-containing products behind the pharmacist's counter (which would mean they could not be sold outside drugstores).
"Although DXM, when formulated properly and used in small amounts, can be safely used in cough suppressant medicines," the FDA says, "abuse of the drug can cause death as well as other serious adverse events such as brain damage, seizure, loss of consciousness, and irregular heart beat." But this sort of thing does not seem to happen very often. "Considering its widespread over the counter (OTC) availability," the FDA concedes, "relatively few reports of serious abuse-related events involving DXM have been published."
DXM has been on the market since 1958, when the FDA approved it as a "nonaddictive substitute for codeine" (which was switched to prescription-only status in an effort to discourage nonmedical use). It is an ingredient in more than 125 OTC products. Yet the FDA cites only five deaths caused by DXM overdoses in the United States, all of them in 2005 and all of them involving not cold remedies but DXM powder purchased for recreational use. By contrast, aspirin causes hundreds of deaths every year.
What about nonfatal events? According to the Drug Abuse Warning Network, there were 3,914 DXM-related emergency room visits in 2008, compared to 7,933 for pseudoephedrine and 39,215 for diphenhydramine, the antihistamine in Benadryl. And while the Drug Enforcement Administration says it is "concerned with the increasing abuse of dextromethorphan, especially among adolescents," the government-sponsored Monitoring the Future Study indicates that nonmedical use of "OTC cough/cold medicines" is down among eighth-graders and 12th-graders since 2006 (the first year the survey asked about this drug category) and up only slightly among 10th-graders, 6 percent of whom reported past-year use in 2009, compared to 5.3 percent in 2006.
"Because of the drug's perceived safety, ease of availability, and desired psychoactive effects, it is sought after by those seeking to alter their mental state," the FDA says. It leaves out another factor in DXM's appeal to teenagers: the drug laws, which increase the cost, effort, and risk involved in obtaining safer alternatives such as marijuana. It's hard to for me to imagine that DXM would have much of a following in the absence of drug prohibition. Maybe I'm biased, since I do not even like the psychoactive effects of a therapeutic dose, which I find so unpleasant that I avoid products containing DXM.
But consider the DEA's description (included in the FDA packet) of "four dose-dependent 'plateaux'":
1st (100–200 mg): Mild stimulation
2nd (200–400 mg): Euphoria and hallucinations
3rd (300–600 mg): Distorted visual perceptions, loss of motor coordination
4th (500-1,500 mg): Dissociative sedation
Which, in the long tradition of anti-drug warnings that also serve as pro-drug publicity, makes DXM sound pretty appealing. A DXM powder user describes his experience here. The Partnership for a Drug-Free America tries to scare you away from the stuff here. Previous Reason coverage of DXM dread here.