Yesterday the FDA finally settled on new rules for acetaminophen in prescription opioid painkillers, and while they're not as draconian as they could have been (a 2009 panel recommended banning the combination altogether), they will limit the amount of acetaminophen to 325 milligrams per pill. Drugs affected include Vicodin—the most commonly prescribed medication in the United States—and Percocet, along other with a few lesser known drugs.
Regardless of the merits of this new wave of regulation, it's worth examining why Vicodin, which is a compound of the opioid painkiller hydrocodone and acetaminophen (a.k.a. Tylenol), is so popular to begin with. Reading The New York Times gives you the impression that it's simply a popular and effective medicine, but there's another benefit to the combination found in Vicodin over straight hydrocodone: It's less regulated.
Pure hydrocodone is a Schedule II drug under the 1970 Controlled Substances Act, whereas hydrocodone compounded with acetaminophen is a more loosely regulated Schedule III drug, supposedly for its lower abuse potential. Wishing to avoid greater scrutiny, doctors prefer prescribing Schedule III substances like Vicodin over purer Schedule II formulations which don't contain liver-damaging acetaminophen. But why does adding a sometimes-unnecessary ingedient make it difficult (but not impossible) to abuse? For the same reason that the FDA is now regulating it: Because it's poisonous, and can even cause fatal liver damage in the quantities necessary to sustain a heavy addiction. Researchers refer to it as an "abuse deterrent formulation"—the modern-day equivalent of the government spiking industrial alcohol during Prohibition. Except rather than blindness-inducing methanol, we now use deafness-inducing acetaminophen.
To be fair to the FDA, they share custody of the scheduling of controlled substances with an alphabet soup of other federal agencies and have comparatively little control over the process. But given all of the ink spilled and time spent regulating the acetaminophen out of Vicodin, it would have been helpful if they had at least acknowledged why it's there in the first place. Simply reclassifying pure hydrocodone as a slightly less controlled Schedule III substance might have worked just as well as this—a heavy-handed, roundabout approach that will take away even more options from pain sufferers.