A summary of the most common chemical descriptors (InChI Key and SMILES codes) for Flucytosine are summarized together with 3D and 2D structures and relevant physico-chemical properties.

What is the Flucytosine?

The molecule Flucytosine presents a molecular formula of C4H4FN3O and its IUPAC name is 6-amino-5-fluoro-1H-pyrimidin-2-one.

Flucytosine (5-fluorocytosine, 5-FC) is a broad-spectrum antifungal medication that is commonly used to treat fungal infections in humans and animals. It is particularly effective against yeasts and fungi that are resistant to other antifungals. Flucytosine is often used in combination with other antifungals, such as amphotericin B or fluconazole, to increase the effectiveness of treatment..

The flucytosine molecule is a small, highly lipophilic compound with a molecular weight of about 130.1 g/mol. It is structurally related to the nucleoside cytosine, with the addition of a fluorine atom at the 5-position. Flucytosine is a prodrug, which means that it is inactive until it is metabolized in the body. Once it is metabolized, flucytosine is converted to the active compound 5-fluorouracil (5-FU), which is a pyrimidine antimetabolite..

Flucytosine works by inhibiting the synthesis of fungal DNA, RNA, and proteins. It does this by inhibiting the enzyme thymidylate synthase, which is responsible for the synthesis of thymidine monophosphate, a nucleotide that is required for DNA synthesis. By inhibiting thymidylate synthase, flucytosine blocks the synthesis of DNA and RNA, which prevents the fungus from growing and reproducing..

Flucytosine is typically administered orally or intravenously, depending on the severity of the infection and the patient's condition. The usual recommended dose is 50-100 mg/kg/day, given in divided doses every 6-12 hours. Flucytosine is metabolized in the liver, and the metabolites are eliminated through the kidneys. It is important to monitor liver and kidney function during treatment with flucytosine, as the drug can cause liver and kidney toxicity in some patients..

Flucytosine is generally well-tolerated, with few serious side effects. The most common side effects are nausea, vomiting, and diarrhea. Rarely, flucytosine can cause more serious side effects, such as anemia, neutropenia (low white blood cell count), and liver and kidney toxicity. It is important to notify a healthcare provider if any side effects occur during treatment with flucytosine..


From all the above, this molecule is a valuable antifungal medication that is effective against a wide range of fungi, including yeasts and fungi that are resistant to other antifungals. It is typically well-tolerated, with few serious side effects. However, it is important to monitor liver and kidney function during treatment and to notify a healthcare provider if any side effects occur..

3D structure

Cartesian coordinates

Geometry of Flucytosine in x, y and z coordinates (Å units) to copy/paste elsewhere. Generated with Open Babel software.

2D drawing


Flucytosine XRECTZIEBJDKEO-UHFFFAOYSA-N chemical compound 2D structure molecule svg


Molecule descriptors

IUPAC name6-amino-5-fluoro-1H-pyrimidin-2-one
InChI codeInChI=1S/C4H4FN3O/c5-2-1-7-4(9)8-3(2)6/h1H,(H3,6,7,8,9)

Other names (synonyms)

IUPAC nomenclature provides a standardized method for naming chemical compounds. Although this system is widely used in chemistry, many chemical compounds have also other names commonly used in different contexts. These synonyms can come from a variety of sources and are used for a variety of purposes.

One common source of synonyms for chemical compounds is the common or trivial names, assigned on the basis of appearance, properties, or origin of the molecule.

Another source of synonyms are historical or obsolete names employed in the past, however replaced nowadays by more modern or standardized names.

In addition to common and historical names, chemical compounds may also have synonyms that are specific to a particular field or industry.

  • 117969-88-7
  • 130256-61-0
  • 1LD
  • 2(1H)-Pyrimidinone, 4-amino-5-fluoro-
  • 2(1H)-Pyrimidinone, 4-amino-5-fluoro-)
  • 2-Hydroxy-4-amino-5-fluoropyrimidine
  • 2-Pyrimidinol, 4-amino-5-fluoro- (9CI)
  • 2-pyrimidinol,4-amino-5-fluoro-
  • 2022-85-7
  • 22P857
  • 4-Amino-5-fluoro-1H-pyrimidin-2-one
  • 4-Amino-5-fluoro-2(1H)-pyrimidinone
  • 4-Amino-5-fluoro-2-hydroxypyrimidine
  • 4-Amino-5-fluoro-2-hyroxypyrimidine
  • 4-Amino-5-fluoro-2-pyrimidinol
  • 4-Amino-5-fluoropyrimidin-2(1H)-one
  • 4-amino-5-fluoro-pyrimidin-2-ol
  • 4-amino-5-fluoropyrimidin-2-ol
  • 5 Fluoro Cytosine
  • 5-FC
  • 5-Flucytosine
  • 5-Fluorocystosine
  • 5-Fluorocytosin
  • 5-Fluorocytosine
  • 5-Fluorocytosine, Antibiotic for Culture Media Use Only
  • 5-Fluorocytosine, nucleoside analog
  • 5-Flurocytosine
  • 5-fluoro cytosine
  • 5-fluoro-cytosine
  • 5-fluorocytocine
  • 5-fluorocytosine Form I
  • 5-fluorocytosine Form II
  • 6-Amino-2-oxo-5-fluoropyrimidine
  • 6-amino-5-fluoro-1,2-dihydropyrimidin-2-one
  • 6-amino-5-fluoro-1H-pyrimidin-2-one
  • 6-amino-5-fluoro-2(1H)-pyrimidinone;5-FLUOROCYTOSINE
  • 6-amino-5-fluoro-3-hydropyrimidin-2-one
  • 6-amino-5-fluoropyrimidin-2(1H)-one
  • A814346
  • AB00444223-16
  • AB00513969
  • AB00513969-02
  • AB00513969_03
  • AB00513969_04
  • AC-11748
  • AM20090149
  • Alcobon
  • Ancoban
  • Ancobon
  • Ancotil
  • Ancotyl
  • BCP02877
  • BCP0726000281
  • BCP9000692
  • BDBM50248003
  • BP-30254
  • BPBio1_000956
  • BSPBio_000868
  • CCG-100837
  • CCG-213434
  • CPD000059047
  • CS-1935
  • Cytosine, 5-fluoro-
  • Cytosine, 5-fluoro- (6CI,7CI,8CI)
  • D00323
  • D83282DT06
  • DB-005380
  • DB01099
  • DSSTox_CID_3059
  • DSSTox_GSID_23059
  • DSSTox_RID_76856
  • EC 217-968-7
  • F-3010
  • F0321
  • FT-0601273
  • FT-0695664
  • Flourocytosine
  • Flucitosina
  • Flucytosin
  • Flucytosine
  • Flucytosine (5-FC)
  • Flucytosine (Ancobon)
  • Flucytosine (JP17/USP/INN)
  • Flucytosine 2.0 mg/ml in Methanol
  • Flucytosine, 5-Fluorocytosine
  • Flucytosine,(S)
  • Flucytosinum
  • Flucytosone
  • Fluocytosine
  • Fluorcytosine
  • Fluorocytosine
  • GS-5578
  • H10295
  • HMS1570L10
  • HMS2051M04
  • HMS2093J05
  • HMS2097L10
  • HMS2233I14
  • HMS3373L05
  • HMS3393M04
  • HMS3655G17
  • HMS3714L10
  • HSDB 3082
  • HY-B0139
  • KS-1060
  • LS40595
  • MFCD00006035
  • MFCD00179326
  • MFCD03547958
  • MLS000069463
  • MLS000759519
  • MLS001076503
  • MLS001424013
  • NC00087
  • NCGC00016599-01
  • NCGC00016599-02
  • NCGC00016599-04
  • NCGC00016599-05
  • NCI60_000093
  • NSC 103805
  • NSC-103805
  • NSC-759130
  • NSC103805
  • NSC759130
  • Opera_ID_178
  • Pharmakon1600-01505429
  • Prestwick0_000934
  • Prestwick1_000934
  • Prestwick2_000934
  • Prestwick3_000934
  • Q238490
  • Ro 2-9915
  • Ro 29915 E/265601
  • Ro-2-9915
  • Ro-29915
  • SB57097
  • SMR000059047
  • SR-01000721885
  • SR-01000721885-5
  • ST028644
  • STK292386
  • SW197278-3
  • SY004438
  • flucytosina
  • flucytosine
  • s1666

Reference codes for other databases

There exist several different chemical codes commonly used in orded to identify molecules:
  • ZINC896546
  • CAS-2022-85-7
  • UNII-D83282DT06
  • AKOS004912683
  • AKOS005063821
  • AKOS015896898
  • AKOS030241326
  • BRD-K82143716-001-15-7
  • DTXSID3023059
  • CHEMBL1463
  • CHEBI:5100
  • Tox21_110515
  • Tox21_110515_1
  • EINECS 217-968-7
  • SPBio_003037
  • SCHEMBL24063
  • SCHEMBL14696800

Physico-Chemical properties

IUPAC name6-amino-5-fluoro-1H-pyrimidin-2-one
Molecular formulaC4H4FN3O
Molecular weight129.09
Melting point (ºC)
Boiling point (ºC)
Density (g/cm3)
Molar refractivity29.2
Topological polar surface area71.8

LogP and topological polar surface area (TPSA) values were estimated using Open Babel software.

The n-octanol/water partition coeficient (Kow) data is applied in toxicology and drug research. Kow values are used, to guess the environmental fate of persistent organic pollutants. High partition coefficients values, tend to accumulate in the fatty tissue of organisms. Molecules with a log(Kow) (or LogP) greater than 5 are considered to bioaccumulate.

TPSA values are the sum of the surface area over all polar atoms or molecules, mainly oxygen and nitrogen, also including hydrogen atoms.

In medicinal chemistry, TPSA is used to assess the ability of a drug to permeabilise cells.

For molecules to penetrate the blood-brain barrier (and act on receptors in the central nervous system), TPSA values below 90 Å2 are required. Thus, molecules with a polar surface area greater than 140 Å2 tend to be poorly permeable to cell membranes.