QUANTITATION OF N-DEMETHYLANTIPYRINE IN BIOLOGICAL SAMPLES AND ISOLATION AND CHARACTERIZATION OF ITS GLUCURONIC ACID CONJUGATE

Abstract

An improved method for quantitating N-demethylantipyrine (N-DEM-AP) in urine by gas chromatography or gas chromatography-mass spectrometry was developed. Recovery of > 90% of N-DEM-AP was achieved by extraction of the sample at pH 1 after addition of 3-amino-1-phenyl-2-pyrazolin-5-one. The coefficient of variation of replicate analyses was 8%. N-DEM-AP was excreted in the urine as a glucuronic acid conjugate. This conjugate was isolated from the urine of an individual receiving antipyrine and purified. The NMR and mass-spectral data are consistent with the conjugate being an O-glucuronide of N-DEM-AP in its enol form. Antipyrine is a drug with antipyretic and analgesic activity.