Flucytosine (5-Fluorocytosine/5-FU) – Antifungals

Let's move on to flucytosine. Now flucytosine is a different class of medication. It also an antimetabolite that's used in cancer chemotherapy. It's eliminated in the urine. So dose adjustments going to be necessary in patients who are, who have renal disease. It is relatively narrow spectrum agent. And it's used almost exclusively in cryptococcus neoformans infections. The mechanism of action, it's actually included into the -- through the cell wall by a membrane permease. And then that concentration inside the cell is actually increasing and accumulative. It's converted by cytosine deaminase from flucytosine to 5-FU. So 5-FU is 5 flourocytosine. 5-FU then blocks the production of thymidine through inhibiting thymidylate synthase. So now you're starting to interfere with actual production of DNA fragments and RNA fragments. When combined with amphotericin B or itraconazole, synergy occurs. So you actually get a very strong combination effect with these two agents together. In terms of toxicity there is a reversible bone marrow depression that you sometimes see, you can sometimes see alopecia as well. So hair loss and of course liver dysfunction. ...