N-HYDROXYPHENACETIN, A NEW URINARY METABOLITE OF PHENACETIN IN THE RAT

  • 1 January 1981
    • journal article
    • research article
    • Vol. 9  (3) , 255-260
Abstract
N-Hydroxylation of aromatic amino compounds is responsible for much of their toxicity. N-Hydroxyphenacetin was found in the urine of rats dosed with the analgesic, 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 h, 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 TLC. 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 of phenacetin was recovered from urine as N-hydroxyphenacetin. It is possible that this value considerably underestimates the extent of phenacetin N-hydroxylation in vivo, as N-hydroxyphenacetin is known to be rapidly degraded in biological systems.