5-Fluorocytosine (syn. Flucytosine) is a fluorinated cytosine (pyrimidine) analog with antifungal activity. First developed in 1957, it is active against Candida and Cryptococcus and is a competitive inhibitor of uracil metabolism. 5-Fluorocytosine is taken up by the fungus and is converted to the cytostatic 5-fluorouracil by cytosine deaminase. 5-Fluorocytosine can also be used in brain tumor research models using the virus Toca 511 which codes for cytosine deaminase. 5-Fluorocytosine is sparingly soluble in water.
