BRAND NAMES
 MECHANISM OF ACTION
Flucytosine is an analogue of a pyrimidine. It is relatively deaminated in the fungi by cytidine deaminase to form 5-Fluorouracil (an important anticancer agent). Thus, flucytosine is a precursor of 5-FU, but does not behave like an anticancer drug, because the cytidine deaminase is not present in the human cells. However, it is still toxic for the normal (human) tissue.
In order for 5-FU to be active or incorporated into the DNA, it must be converted to 5-FdUMP. In this form, it is able to inhibit thymidylate synthase, thus reducing the pool of thymidylate. Consequently, when the non-correct nucleotide is incorporated into the DNA, upon activation of the repair system that is to replace the wrong base pair, there will be a depletion or lack of the correct dTMP to replace the base.
- Candida albicans
- Due to reduced activation of Flucytosine
- Can be administered orally (unlike Amphotericin B)
- Can cross BBB (unlike Amphotericin B)
- Eliminated mostly by the kidney
Flucytosine can be used in combination with Amphotericin B for the treatment of cryptococcal meningitis. This is an example of synergism – by disrupting the fungal membrane, Amphotericin B will facilitate the entrance of flucytosine. This synergism allows the use of a reduced dose of both drugs. Flucytosine is not commonly used because of its very narrow spectrum. It is mainly used in combination with Amphotericin B.
 PREGNANCY AND LACTATION
 SIDE EFFECTS
Flucytosine has systemic side effects that includes bone marrow depression. Its side effects are also similar to those observed with anticancer drugs.
 RELATED LINKS
|Ergosterol target : Cell membrane target||Azoles (lanosterol 14 alpha-demethylase inhibitors) : Ergosterol inhibitors||Imidazoles||Topical: Bifonazole • Clotrimazole • Econazole • Fenticonazole • Ketoconazole • Isoconazole • Miconazole • Sertaconazole • Tioconazole|
|Triazoles|| Topical: Fluconazole • Terconazole|
Systemic: Fluconazole • Itraconazole • Posaconazole • Voriconazole
|Polyene antimycotics (ergosterol binding; they form pores in the membrane)|| Topical: Nystatin |
Systemic: Amphotericin B
|Allylamines (squalene epoxidase inhibitors) : Ergosterol inhibitors|| Topical: Amorolfine • Naftifine • Terbinafine |
|Echinocandins (β-glucan synthase inhibitors) : Cell wall target||Anidulafungin • Caspofungin • Micafungin|
|Pyrimidine analogues / Thymidylate synthase inhibitors : Nucleic acid inhibitors||Flucytosine|