Structural determination of a glucuronide conjugate of flucytosine in humans.

The structure of a glucuronide metabolite of flucytosine (FC; 5-fluorocytosine), found in the urine of all patients treated with this antifungal drug, was determined. This compound is the O2-beta-glucuronide of FC. Its structure was established after isolation from urine and by comparing its spectroscopic characteristics with those of three FC glucuronides previously synthesized. This study is the first report of the identification of a glucuronide of a fluoropyrimidine drug in humans.