Drug Index


Synonym :

5- Fluorocytosine

Mechanism :

Flucytosine is taken up by fungal organisms via the enzyme cytosine permease. In the fungal cell, flucytosine is rapidly converted to fluorouracil by the enzyme cytosine deaminase. Fluorouracil is converted into several active metabolites, which inhibit protein synthesis by being incorporated into fungal RNA or interfere with the biosynthesis of fungal DNA through the inhibition of the enzyme thymidylate synthetase.

Indication :

  • Candidiasis
  • Cryptococcus infection

Contraindications :

Flucytosine should not be used in patients with a known hypersensitivity to the drug. Blood count and liver enzymes should be monitored before and during therapy. Caution should be exercised in patients with pre-existing bone marrow depression.

Dosing :

80-160 mg/kg/day orally in 4 divided doses.
50-150 mg/kg/day orally in 4 divided doses.

Adverse Effect :

Myocardial toxicity, cardiac arrest, ventricular dysfunction, rash, urticaria, pruritus, photosensitivity, respiratory arrest, chest pain, dyspnea, azotemia, crystalluria, creatinine and BUN elevation, renal failure, nausea, emesis, abdominal pain, diarrhea, dry mouth, anorexia, gastrointestinal hemorrhage, duodenal ulcer, hepatic dysfunction, ulcerative colitis.

Interaction :

Cytosine arabinoside: Has been reported to inactivate the antifungal activity of flucytosine by competitive inhibition.
Drugs which impair glomerular filtration may prolong the biological half-life of flucytosine.

Renal Dose :

Dose in Renal Impairment GFR (mL/min)
20-4050 mg/kg 12 hourly
10-2050 mg/kg 24 hourly
<1050 mg/kg then dose according to levels. Dose of 0.5–1 g daily is usually adequate

Dose in Patients undergoing Renal Replacement Therapies
CAPDDialysed. Give 50 mg/kg daily in 4 divided doses. Monitor levels
HDDialysed. Dose as in GFR<10 mL/ min, given post dialysis. Monitor trough level pre dialysis, and reduce post-dialysis dose accordingly
HDF/High fluxDialysed. Dose as in GFR<10 mL/ min, given post dialysis. Monitor trough level pre dialysis, and reduce post-dialysis dose accordingly
CAV/VVHDDialysed. Give dose as in GFR=10–20 mL/min and monitor blood levels, pre dose

Hepatic Dose :

No dosage adjustment required.
01/24/2024 03:01:11 Flucytosine
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