FLUCYTOSINE CONVERSION TO FLUOROURACIL IN HUMANS - DOES A CORRELATION WITH GUT FLORA STATUS EXIST - A REPORT OF 2 CASES USING F-19 MAGNETIC-RESONANCE SPECTROSCOPY

A relationship between the gut flora level, particularly gram-negative enterobacilli, and the in vivo flucytosine conversion to fluorouracil has been observed in humans from the fluorine-19 magnetic resonance spectroscopy analysis of urine from two patients treated with the flucytosine- (6 to 9 g/day) amphotericin B (1 mg/kg/day) combination. Indeed the percentage of fluorouracil metabolites was extremely low (< 0.6% of total fluorinated compounds excreted) when the number of enterobacillary colonies was low (< 10(3)) and higher (3.5 to 8.8%) when enterobacillary colonies were under reconstitution or in the normal range (10(5) to 10(8)). The intestinal microflora assessment may therefore be of high interest to predict the risk of an additive flucytosine-induced myelotoxicity suspected to be due to fluorouracil during flucytosine chronic therapy.