Dosing and uses of Flucytosine (Ancobon, 5-FC)
Adult dosage forms and strengths
capsule
- 250mg
- 500mg
Candidiasis/Cryptococcus Infection
50-150 mg/kg/d div q6hr PO
Adjust dose for renal dysfunction
Other Indications & Uses
Off-label: chromomycosis
Pediatric dosage forms and strengths
capsule
- 250mg
- 500mg
Candidiasis/Cryptococcus Infection
Child: same as adult dosing; 50-150 mg/kg/d div q6hr PO
Neonates (<28 days old): 80-160 mg/kg/d div q6hr PO
Adjust dose for renal dysfunction
Flucytosine (Ancobon, 5-FC) adverse (side) effects
Frequency not defined
Confusion
Headache
Hallucinations
Dizziness
Drowsiness
Psychosis
Parkinsonism
Ataxia
Sedation
Rash
Photosensitivity
Pruritus
Urticaria
Temporary growth failure
Hypoglycemia
Hypokalemia
Nausea
Vomiting
Diarrhea
Abdominal pain
Loss of appetite
Bone marrow suppression
Anemia
Leukopenia
Thrombocytopenia
Elevated liver enzymes
Hepatitis
Azotemia
Peripheral neuropathy
Paresthesia
Weakness
Hearing loss
Elevated BUN and serum creatinine
Renal failure
Respiratory arrest
Anaphylaxis
Warnings
Black box warnings
Use extreme caution in patients with renal impairment
Monitor hematologic, renal, and hepatic function
Review instructions thoroughly before administration
Contraindications
Hypersensitivity
Cautions
Bone marrow depression, renal impairment, blood dyscrasias
Monitor to maintain blood levels <100 mg/L
Pregnancy and lactation
Pregnancy category: C
Lactation: excretion in milk unknown/not recommended
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Flucytosine (Ancobon, 5-FC)
Mechanism of action
Competitive inhibition of purine, pyrimidine uptake
Pharmacokinetics
Absorption: 75-90%
Distribution: into CSF, aqueous humor, joints, peritoneal fluid, & bronchial secretions
Protein Bound: 2-4%
Half-life elimination: 3-8 hr; anuria: up to 200 hr; end-stage renal disease: 75-200 hr
Peak Plasma Time: 2-6 hr
Metabolism: minimally hepatic
Excretion: urine (75-90% as unchanged drug)
