[2][3] Common side effects include bone marrow suppression, loss of appetite, diarrhea, vomiting, and psychosis.

[8] Flucytosine by mouth is used for the treatment of serious infections caused by susceptible strains of Candida or Cryptococcus neoformans.

In some countries, treatment with slow intravenous infusions for no more than a week is also a therapeutic option, particular if the disease is life-threatening.

The issue has been raised because traces of 5-fluorouracil, which is a known carcinogen, are found in the colon resulting from the metabolization of flucytosine.

Flucytosine may increase the toxicity of amphotericin B and vice versa, although the combination may be life-saving and should be used whenever indicated (e.g., cryptococcal meningitis).

[citation needed] Symptoms and their severities are unknown, because flucytosine is used under close medical supervision, but expected to be an excess of the usually encountered side effects on the bone marrow, gastrointestinal tract, liver and kidney function.

[citation needed] Two major mechanisms of action have been elucidated: Flucytosine is active in vitro as well as in vivo against some strains of Candida and Cryptococcus.

Limited studies demonstrate that flucytosine may be of value against infections with Sporothrix, Aspergillus, Cladosporium, Exophiala, and Phialophora.

[7] This cost of flucytosine is more than 100-fold higher in the U.S. than in the United Kingdom and Europe via Meda AB Pharmaceuticals.

In some countries, such as Switzerland, flucytosine has been licensed to treat cats, dogs and birds (in most cases together with amphotericin B) for the same indications as in humans.