Flucytosine is a synthetic fluorinated pyrimidine antifungal agent primarily used in the treatment of serious systemic fungal infections, particularly those caused by Cryptococcus species and Candida species. It acts as a prodrug that is converted inside fungal cells into 5-fluorouracil, which then interferes with fungal DNA and RNA synthesis, leading to inhibition of cell growth. Historically, flucytosine was first synthesized in the 1950s as part of research into antimetabolite compounds, initially investigated for anticancer properties but later found to have potent antifungal activity. It was introduced clinically in the 1960s and became a valuable treatment option, especially in combination with amphotericin B, for cryptococcal meningitis and severe systemic candidiasis. Over the years, its use has been carefully monitored due to potential bone marrow toxicity and the rapid development of resistance when used as monotherapy, making combination therapy the standard approach in serious infections.
