SEPARATION AND IDENTIFICATION OF PHASE-I AND PHASE-II [(1)4C]ANTIPYRINE METABOLITES IN RAT AND DOG URINE

A simple and accurate HPLC procedure was developed to quantify, in a single run, all phase I and phase II [C-14]antipyrine metabolites that occur in rat and dog urine. All metabolites were subjected to thermospray-LC-MS and EI-MS in order to establish their structure. The rat metabolizes antipyrine to eight major metabolites, six of which are conjugated; 1.4% of the dose was excreted unchanged, 18.9% in a free form, 30.6% as sulfates and 21.1% as glucuronides. The dog metabolizes antipyrine to four metabolites, all as sulfate (61.0% of the dose) or glucuronide conjugates (16.2% of the dose).