Studying APAP metabolism in a cohort of intoxicated patients using HRMS-based profiling: Detection of catechol and delayed thiomethyl metabolites

Acetaminophen (APAP) overdose is one of the most important causes of drug-induced liver injury worldwide. Hepatotoxicity induced by APAP is mainly caused by the production of N-acetyl-p-benzoquinone imine (NAPQI), a highly reactive intermediate. Although, the medical management of APAP intoxication is well known, research is still ongoing to identify markers that could help to predict adverse issues after APAP intoxication. In this study, we aimed to study APAP biotransformation pathways in a cohort of patients with proven acute APAP intoxication to identify new biomarkers using state-of-the-art high-resolution mass spectrometry (HRMS) methodologies that could help improve the diagnosis of intoxication as well as patient follow-up. We used a cohort of 37 patients whom blood plasma samples were stratified according to the collection time after APAP intoxication. Our results showed that direct phase II metabolites from glucuronidation and sulfation pathways remain the main markers of APAP consumption. Our study also revealed that several oxidative pathways produce significant metabolites (including catechol ones) that could also help to monitor the intoxication and the elimination of the hepatotoxic NAPQI. In particular, significant levels of thiomethyl metabolites derived from the glutathione-NAPQI conjugates could be detected with a delay in their kinetics of appearance.