N-hydroxyphenacetin, a new urinary metabolite of phenacetin in the rat.
N-Hydroxyphenacetin has been found in the urine of rats dosed with phenacetin, extending previous reports that phenacetin is N-hydroxylated by liver microsomes in vitro. After an oral dose of phenacetin (500 mg/kg) urine was collected for 24 hr, conjugates hydrolyzed with extract of Helix pomatia, and the metabolites extracted with dichloromethane and treated with diazomethane. Methylation of N-hydroxyphenacetin produced a stable derivative, N-methoxyphenacetin, which was separated from most other metabolites by thin layer chromatography. Identification of N-methoxyphenacetin was by combined gas chromatography-mass spectrometry and comparison with the synthetic reference compound. Quantification by gas chromatography with flame-ionization detection showed that 0.023% of the dose phenacetin was recovered from urine as N-hydroxyphenacetin. It is probable that this value considerably underestimates the extent of phenacetin N-hydroxylation in vivo, inasmuch as N-hydroxyphenacetin is known to be rapidly degraded in biological systems.
D000818:Animals; D001711:Biotransformation; D008401:Gas Chromatography-Mass Spectrometry; D008297:Male; D010615:Phenacetin / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000652:urine; D051381:Rats
C008068:N-hydroxyphenacetin; D010615:Phenacetin