From my fairly limited understanding, much of the time medications are said to be damaging to the liver, what is meant is that the process of breaking them down causes the formation of free radicals, which then attack the local liver cells. Is this usually the case?

For example, acetaminophen (paracetamol, Tylenol, Calpol, Panadol depending on where you live) is broken down in the liver through three pathways, glucoronidation, sulfation, and a third involving the cytochrome P450 enzymes. This third pathway entails breakdown chiefly by CYP2E1 and CYP3A4 through the intermediate NAPQI, which is a strong oxidizer. Too much acetaminophen, or a little over a long period of time, leads to a buildup of NAPQI, which causes oxidation of liver cells and subsequent liver damage.

Is it the case that usually, when drugs are known to cause liver damage under certain conditions (such as high dosage or extended use), it's because the drug is broken down in the liver into reactive chemical species that cause oxidative stress on the local liver tissues?

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