Though most people don’t know it, the acetaminophen (better known by its brand name Tylenol) can often be the most deadly ingredient in prescription pain medications that contain opioids like codeine. Although the damage linked to opioid overdose can be entirely reversed with an antidote if the victim is treated quickly, high doses of acetaminophen (which is also found in cold medications) can irreparably damage the liver—and there is no comparable antidote.
That’s why the FDA Thursday began phasing in a requirement that painkillers that include both acetaminophen and opioids contain no more than 325 mg of acetaminophen per pill as well as display a boxed warning about the risk of irreversible liver damage from large doses. (More on Time.com: Mind Over Matter: Can Zen Meditation Help You Forget About Pain?)
Although the inclusion of acetaminophen in the combination pain-killers is intended in part to deter abuse of mild opioids, ironically, for some pain patients it’s the ingredient that proves more dangerous.
In a statement, Sandra Kweder, MD, deputy director of the Office of New Drugs in the FDA’s Center for Drug Evaluation and Research said, “Overdose from prescription combination products containing acetaminophen account for nearly half of all cases of acetaminophen-related liver failure in the U.S., many of which result in liver transplant or death.”
Similar attempts to deter alcohol abuse during Prohibition by including poisonous chemicals in industrial alcohol that was being diverted for use by bootleggers resulted in the deaths of roughly 10,000 people; more recently, chemicals added to anti-anxiety and pain medications to prevent injection have instead resulted in limb amputations after the substances caused blood clots or other complications. (More on Time.com: Suffer from Migraines? FDA Says Try Botox Injections)
Still, the intention behind partnering opiods with acetaminophen is clearly laudable—as is the new regulation to limit its potential dangers in large doses.