Fluorocytosine Chemical Information

Fluorocytosine, or 5-fluorocytosine, a fluorinated pyrimidine analogue, is a synthetic antimycotic drug.

It is structurally related to the cytostatic fluorouracil and to floxuridine. It is available in oral and in some countries also in injectable form. A common brand name is Ancobon. Fluorocytosine was first synthesized in 1957 but its antifungal properties were discovered in 1964. The drug is dispensed in capsules of 250 mg and 500 mg strength. The injectable form is diluted in 250 mL saline solution to contain 2.5 g total (10 mg/mL). The solution is physically incompatible with other drugs including amphotericin B.

1. Properties

Name:Fluorocytosine

EINECS:217-968-7

Molecular Formula:C4H4FN3O

CAS Registry Number:2022-85-7

InChI:InChI=1/C4H4FN3O/c5-2-1-7-4(9)8-3(2)6/h1H,(H3,6,7,8,9)

Appearance:white crystalline solid

Molecular Weight:129.09

Density:1.73g/cm3

Boiling Point:298

Melting Point:296°C

Flash Point:296

Storage Temperature:2-8°C

Refractive index:1.613

Solubility:Water Solubility : 1.5g/100mL (25 °C)

Usage:5-FC is a toxic antifungal/antimicrobial agent

2. Safety Information

Hazard Codes:Xn,T,Xi

Risk Statements : 40-36/37/38

Safety Statements:  22-24/25-45-36/37-36/37/39-27-26

WGK: Germany  2

RTECS:  HA6040000

F:10-23

Hazard Note:  Toxic/Light Sensitive

HazardClass:  IRRITANT, LIGHT SENSITIVE 

3. Contraindications and cautions

All patients receiving flucytosine should be under strict medical supervision.

*Hematological, renal and liver function studies should be done frequently during therapy (initially daily, twice a week for the rest of treatment).

*Patients with preexisting bone marrow depression and liver impairment should be treated with caution.

*Concomitant treatment with brivudine is an absolute contraindication.

*Patients treated with drugs compromising bone marrow function (e.g. cytostatics) should be treated carefully. Blood cell counts should be taken very frequently.

*Patients with renal disease should receive flucytosine cautiously and in reduced doses. *Guidelines for proper dosing exist. Serum level determinations are mandatory for these patients.