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. Author manuscript; available in PMC: 2021 Nov 1.
Published in final edited form as: Drug Metab Rev. 2020 Oct 14;52(4):472–500. doi: 10.1080/03602532.2020.1832112

Figure 3. Proposed mechanisms of NAPQI formation.

Figure 3.

Initially, it was thought that formation of the reactive metabolite of APAP may precede through N-hydroxylation (A) or epoxidation (B), as shown. These mechanisms were proven to be incorrect. (C) It is now thought that APAP is directly oxidized by a two-electron oxidation, a previously unrecognized cytochrome P-450 mechanism. Once formed, NAPQI readily reacts with sulfhydryl groups, such as on GSH or cysteine residues in proteins.