A reversed-phase high-performance liquid chromatographic (RP-HPLC) method employing W-detection (248 nm) I 5 ym Resolve C18 as stationary phase (in a 8 x 100 mm Waters Radial-Pak cartridge) and 0.1 M potassium phosphate monobasic/methanol/glacial acetic acid (95:4:1, VJVJV) as mobile phase was developed for the rapid and simultaneous determination of paracetamol and its major metabolites (its glucuronide and sulphate conjugates) in urine. The method requires only minimal sample preparation and chromatographic run time is only 6 min. For determination of paracetamol, the precision (inter-assay RSD ranged from 1.60-0.66% between 5 and 3257 Copyright 0 1995 by Marcel Dekker, Inc Downloaded by [University of Calgary] at 19:05 04 February 2015 3258GOICOECHEA, LOPEZ DE ALDA, AND VILA-JATO 100 pg mL-l) and 1imit.s of detection (2 ng mL-l) were satisfactory, as were these parameters for determination of the major metabolites. In the course of studies on paracetamol bioavailability and metabolism, over 1500 samples have been assayed using this method. Herein we report its use for monitoring of the levels of paracetamol and its major metabolites in the urine of fifteen normal healthy volunteers given a single oral dose of 500 mg.
The influence of dose on the absorption and presystemic biotransformation of acetaminophen was studied in 15 healthy volunteers after administration of 3 different oral doses (250 mg, 500 mg, 750 mg) following a 3 x 3 Latin Square Design. The analytical method developed (High Performance Liquid Chromatography, HPLC) allows the rapid and simultaneous determination of acetaminophen and its major metabolites (its glucuronide and sulphate conjugates) by direct injection of urine samples. The statistical analysis did not reveal significant differences (alpha < 0.05) among treatments in the percentage of dose excreted and MRT and VRT values. Consequently, our results indicate that the absorption and biotransformation of acetaminophen is not affected by the dose in the usual therapeutical range.
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