|
Mode of Action: |
| Flucytosine is converted by cytosine deaminase in fungal cells to fluorouracil, which then interferes with RNA and protein synthesis. Fluorouracil is metabolized to 5-fluorodeoxyuridylic acid, an inhibitor of thymidylate synthetase. DNA synthesis is then also halted. Mammalian cells do not convert large amounts of flucytosine to fluorouracil and, thus, are not affected at usual dosage levels. |
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|
Fungal Resistance: |
| Resistance to flucytosine can develop rapidly even during the course of treatment; this has restricted its use as the sole treatment for mycotic infections. The mechanisms of resistance are not completely understood. |
| |
|
Antifungal Spectrum: |
| The following are the main organisms usually sensitive to flucytosine:
Cryptococcus
neoformans
,
Candida
albicans
, other
Candida
spp
,
Torulopsis
glabrata
,
Sporothrix
schenckii
,
Aspergillus
spp
, and agents of chromoblastomycosis (
Phialophora
,
Cladosporium
). The other fungi responsible for systemic mycoses and dermatophytes are resistant to flucytosine. |
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