Which substance is metabolized and removed by the liver?

• A. DDT
• B. Acetaminophen (Tylenol)
• C. Ethylene glycol
• D. Cyanide

Answer: (B)

The liver is the primary site where many drugs are chemically transformed to more water-soluble forms so they can be cleared from the body. Acetaminophen is a classic example of this process. In the liver, most of it is conjugated to glucuronide and sulfate and then eliminated in urine. A small portion is oxidized by cytochrome P450 to a reactive metabolite called NAPQI, which is normally kept in check by glutathione. When doses are high, glutathione stores are depleted, NAPQI accumulates, and liver cells can be damaged. So acetaminophen is the substance most clearly processed and removed by hepatic metabolism.

While other substances also undergo liver metabolism, acetaminophen provides the clearest link to how hepatic detoxification and conjugation lead to elimination, and it highlights why overdoses pose a liver injury risk.