1. It has been suggested that acetaminophen (APAP)-protein adducts can be measured in circulation to diagnose APAP-induced liver injury. However, the full-time course of plasma adducts has not been studied specifically in early-presenting overdose patients. In fact, surprisingly little work has been done on the metabolism of APAP after overdose in general. 2. We measured APAP, five APAP metabolites and APAP-protein adducts in plasma samples from early- and late-presenting overdose patients, and APAP-protein adducts in culture medium from HepaRG cells. 3. In contrast to earlier rodents studies, we found that APAP-protein adducts were lower at early time points and peaked around the time of peak liver injury, suggesting that these adduct levels may take longer to become elevated or remain elevated than previously thought. 4. APAP and its major metabolites were elevated in plasma at early time points and rapidly decreased. 5. Although clinical measurement of APAP-protein adducts holds promise as a diagnostic tool, we suggest caution in its interpretation in very early-presenting patients. Our data also support the idea that sulfation is saturated even at low doses but glucuronidation has a much higher capacity, highlighting the importance of glucuronidation in APAP metabolism.
Keywords: Biomarkers; glucuronidation; hepatotoxicity; protein binding; sulfation.