Tylenol and alcohol: why the liver is the concern
Acetaminophen, the active ingredient in Tylenol, is broken down by the liver. A clinical review of acetaminophen liver injury lists concurrent alcohol use, along with other medicines, genetics and nutrition, among the factors that influence how susceptible someone is and how severe the injury can be. NIAAA's hangover guidance also flags the combination of acetaminophen and alcohol as a liver risk.
Acetaminophen also hides in many cold, flu and sleep products, so it is easy to take more than you realize. If you have been drinking, check every label for acetaminophen and talk to a pharmacist before taking it.
Sources: Bunchorntavakul & Reddy, 2013: Acetaminophen-related hepatotoxicity; Hangovers: causes, remedies, and safety
