Flucytosine–when and how to use this important antifungal

To many clinicians, antifungals are like a black box—obscure and unknown. Our Antimicrobial Stewardship Essentials course will change that! In this video, you'll learn about the mechanism of action, side effects, indications, and contraindications of flucytosine–an important antifungal.

Each day, patients die of bacterial infections for which no active agents are available. This course will familiarize you with the wide variety of antimicrobial agents available, as well as their mechanisms of action, spectrum of activity, and toxicity profiles, so you can be more selective in choosing an agent when one is required and do your part to delay antimicrobial resistance.

[00:00:00] Fungi that are susceptible to flucytosine or 5-fluorocytosine possess two enzymes, one which allows the drug to enter the cell and the other which converts the drug to 5-fluorouracil, an anti-cancer drug which acts on fungal nucleic acids as a chain terminator killing the organism. The primary use of flucytosine

[00:00:30] is in the first phase of treatment for Cryptococcal meningitis. It has been shown that initial therapy with amphotericin B plus flucytosine for the first two weeks of treatment, followed by flu cortisol for the duration of treatment is superior to fluconazole alone. While not first-line therapy, flucytosine has also been used and invasive candidiasis and candida urinary tract infections since the agent

[00:01:00] is concentrated in urine. The toxicity of flucytosine prohibits its routine use in clinical mycology. Conversion of flucytosine to 5-fluorouracil leads to bone marrow suppression with prolonged use. And as an anticancer drug, 5-FU can disturb intestinal mucosal cells. The drug has this effect on cells which normally have a rapid turnover rate. The initial symptoms of toxicity

[00:01:30] to the GI tract may be diarrhea. Physicians unaware of this untoward effect may fail to discontinue the drug. Severe cases of intestinal perforation have occurred. Flucytosine should be used in consultation with an infectious disease specialist and close monitoring of bone marrow function and alertness for diarrhea caused by its effect on the GI mucosa is crucial.