N-acetyl-p-benzoquinone imine (NAPQI)

N-acetyl-p-benzoquinone imine (NAPQI) is a highly reactive and toxic metabolite produced during the hepatic metabolism of acetaminophen (paracetamol). Under normal therapeutic dosing, only a small fraction of acetaminophen is converted to NAPQI via cytochrome P450 enzymes—primarily CYP2E1 and CYP1A2. This minor amount is rapidly detoxified through conjugation with glutathione. However, in cases of overdose or when glutathione reserves are depleted, excess unconjugated NAPQI accumulates and binds covalently to cellular macromolecules, particularly in the liver. This leads to oxidative stress, mitochondrial dysfunction, protein damage, and ultimately cell death—manifesting clinically as acute hepatic failure. The primary clinical intervention for toxicity is administration of the antioxidant precursor N-acetylcysteine[2][3][5]. While crucial for understanding drug-induced liver injury mechanisms and antidote development, NAPQI itself is not considered a therapeutic target such as an enzyme or receptor; rather it represents a toxic intermediate responsible for adverse drug reactions. **Note:** "Acetaminophen metabolite NAPQI" refers specifically to this reactive intermediate; it is not itself a receptor or classical drug target but rather an important molecule in pharmacology/toxicology contexts[2][3].

Other names

NAPBQIN-acetyl-4-benzoquinone imineacetaminophen toxic metabolite

Covalent binding to cellular proteins after glutathione depletion - Induction of oxidative stress and cell death pathways