The combinations at first give them a quicker high, but then can suppress their breathing and heart function, which is very dangerous.
Speaking only for himself and not the ASA, Entrup said he wouldn't support making DXM a prescription-only cough remedy because it's generally safe. But he would support restrictions keeping it out of the hands of those under 18: "I personally feel that it should be [restricted], just as any other type of medication. I think there should be warnings about combining these types of things."
Death from DXM abuse is rare, because high doses often induce vomiting, but most deaths are caused by taking DXM in combination with other medications. Health officials worry about combining it not only with stimulants, but also with some classes of antidepressants, which can cause life-threatening serotonin syndrome, which requires hospital treatment.
These dangers have been on the radar screen of the American Association of Poison Control Centers, which published guidelines on out-of-hospital management of DXM poisoning in the journal Clinical Toxicology in September 2007; emergency room doctors say DXM poisoning can come from a single overdose, or chronic usage.
In hundreds of pages of briefing materials posted by the FDA in advance of Tuesday's Drug Safety and Risk Management Advisory Committee hearing, agency scientists analyzed sales and abuse of products containing DXM.
"Although DXM abuse has been recognized since the 1960s, the drug's misuse has become more common. The drug is abused by individuals of all ages, but its abuse by teenagers and young adults is of particular concern," scientists wrote. They said its "perceived safety, ease of availability, and desired psychoactive effects" make it an easy means of getting high.
In an August 2010 fact sheet included in the hearing briefing materials, the Drug Enforcement Administration warned that DXM abuse is fueled by easy access and "extensive 'how-to' abuse information on various websites."
Even former users said it was easy to find the levels at which DXM produces mind-altering effects: 100-200 mg for mild stimulation, 200-400 mg for euphoria and hallucinations. In May 2005, writer Jennifer Henley Daniel offered her own reflections on Robo-tripping when she was 16.
In that piece, posted on the now-defunct Arriviste Press website, Daniel said the website of the National Drug Intelligence Center tells you "everything you need to know about procuring DXM and abusing the hell out of it." Daniel said she found particularly helpful photos of "all the DXM-containing products, along with other possibilities to be found on the streets -- like the tablets containing a mixture of ketamine and DXM." She said the website, however, had "no images of dead 14-year-olds or after-school-special testimonies from hospital patients bleeding from their eyeballs after eating too much Coricidin HPB."
The Consumer Healthcare Products Association, which represents manufacturers, opposes any restrictions on sales to adults. In the CHPA Briefing Book filed with the FDA before Tuesday's hearing, CHPA said non-prescription dextromethorphan gives millions of Americans relief from coughing.