Acetaminophen (APAP) is a commonly used analgesic and antipyretic drug that can cause liver injury, liver necrosis, and liver failure. APAP-induced liver failure (AILF) is associated with depletion of glutathione and the increased formation of APAP protein adducts from the toxic NAPQI metabolite. There is a hypothesized detoxifying pathway where vitamin C ascorbylates and conjugates the hepatotoxic metabolite N-acetyl-p- benzoquinone imine (NAPQI). If the hypothesized metabolite is found, the protocol for treating APAP overdose could be changed from giving large amounts of the drug acetylcysteine to giving intravenous vitamin C. To find the hypothesized metabolites, we collected urine from 10 male subjects’ after ingestion of 1000 mg of APAP. The urine was prepared for analysis through saturation with sodium chloride, liquid-liquid extraction and analysis of the extract for metabolites by LC-HRMS/MS. The major metabolites found in the urine collected for eight hours after APAP ingestion (T8) include APAP, APAP-sulfate, APAP- glucuronide, APAP-mercapturate, and 2-hydroxyacetaminophen sulfate. The hypothesized ascorbylated NAPQI was not found in the urine. LC-HRMS/MS can simultaneously quantify APAP, its major metabolites (APAP-sulfate and APAP- glucuronide) in urine samples. Follow-up studies are needed to determine if the secondary pathway through ascorbate conjugation is possible with APAP.
Funding Statement (additional comments about funding)
This project was funded by The National Institute of Food and Agriculture (NIFA) which is part of the US Department of Agriculture (USDA) and Dr. Fred Stevens’ OSU College of Pharmacy faculty development funds.