Explain why combining alcohol with acetaminophen is hazardous to the liver.

• A. Alcohol reduces acetaminophen metabolism, reducing toxicity.
• B. Alcohol induces CYP2E1, increasing formation of toxic NAPQI; glutathione depletion reduces detox capacity.
• C. Acetaminophen blocks alcohol dehydrogenase.
• D. Alcohol and acetaminophen compete for the same receptor.

Answer: (B)

When the liver processes acetaminophen, a small amount is converted into a toxic compound called NAPQI. Under normal use, this toxin is quickly neutralized by glutathione and safely eliminated. Alcohol changes this balance by inducing the CYP2E1 enzyme in the liver, which shunts more acetaminophen into the pathway that makes NAPQI. At the same time, alcohol depletes glutathione stores, weakening the liver’s ability to detoxify that toxin. With more NAPQI produced and less glutathione available, NAPQI can accumulate and damage liver cells, increasing the risk of serious liver injury, especially with regular or heavy drinking.

The other ideas aren’t accurate: alcohol does not protect by reducing acetaminophen metabolism; it can actually raise the amount of the toxic metabolite formed. There is no receptor competition between alcohol and acetaminophen, and they don’t interact by blocking each other’s enzymes in a way that would reduce toxicity.