Repetitive microvolumetric sampling and analysis of acetaminophen and its toxicologically relevant metabolites in murine plasma and urine using high performance liquid chromatography.

Acetaminophen is a widely used, nonprescription analgesic and antipyretic drug which can cause severe hepatic and renal cellular necrosis. Analysis of plasma and urinary concentrations of acetaminophen metabolites can facilitate an understanding of the relation of enzymatic pathways involved in the bioactivation and detoxification of acetaminophen to its cellular toxicity. There is a marked interindividual variability in the activity of these enzymatic pathways which play a critical role in the modulation of acetaminophen toxicity. A similar interindividual variability occurs in the in vivo temporal disposition of acetaminophen and its metabolites. Accordingly, optimal in vivo methods would permit repetitive sampling from the same animals, as opposed to sacrificing groups of different animals for each time point. This is particularly difficult in smaller rodents such as the mouse, where generally a single blood sample is obtained by cardiac puncture, often under conditions of general anesthesia which can affect drug metabolism and toxicity. A microvolumetric technique for repetitive blood sampling in individual mice, combined with a simple, high performance liquid chromatographic assay for acetaminophen and its toxicologically relevant metabolites is reported here. Data are presented for the disposition of acetaminophen and its metabolites in murine plasma, feces, and urine.