Paracetamol/
acetaminophen (
N-acetyl-p-aminophenol,
APAP) is a top selling
analgesic used in more than 600 prescription and non-prescription
pharmaceuticals. To study efficiently some of the potential undesirable effects associated with increasing
APAP consumption (e.g., developmental disorders,
drug-induced liver injury), there is a need to improve current
APAP biomonitoring methods that are limited by
APAP short half-life. Here, we demonstrate using high-resolution mass spectrometry (HRMS) in several human studies that
APAP thiomethyl metabolite conjugates (S-methyl-3-thioacetaminophen sulfate and S-methyl-3-thioacetaminophen sulphoxide sulfate) are stable
biomarkers with delayed excretion rates compared to conventional
APAP metabolites, that could provide a more reliable history of
APAP ingestion in epidemiological studies. We also show that these
biomarkers could serve as relevant
clinical markers to diagnose
APAP acute intoxication in overdosed patients, when free
APAP have nearly disappeared from blood. Using in vitro liver models (HepaRG cells and primary human hepatocytes), we then confirm that these thiomethyl metabolites are directly linked to the toxic N-acetyl-
p-benzoquinone imine (
NAPQI) elimination, and produced via an overlooked pathway called the thiomethyl shunt pathway. Further studies will be needed to determine whether the production of the reactive hepatotoxic
NAPQI metabolites is currently underestimated in human. Nevertheless, these
biomarkers could already serve to improve
APAP human biomonitoring, and investigate, for instance, inter-individual variability in
NAPQI production to study underlying causes involved in
APAP-induced hepatotoxicity. Overall, our findings demonstrate the potential of exposomics-based HRMS approach to advance towards a better precision for human biomonitoring.