flucytosine; 5-fluorocytosine (Ancobin, 5-FC)
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Introduction
Tradename: Ancobin.
Indications
- used in combination with amphotericin B in treatment of fungal meningitis
- used in combination with susceptible fungal infections, generally Candida or Cryptococcus
- resistance develops rapidly when used alone
Dosage
50-150 mg/kg/day PO divided QID
Tabs: 250 & 500 mg. Dose adjustment in renal failure:
| creatinine clearance | dose |
|---|---|
| > 40 mL/min | 50-100 mg/kg/day |
| 20-39 mL/min* | 25-50 mg/kg/day |
| < 19 mL/min | 12.5-25 mg/kg/day |
* same dose for continuous arteriovenous hemofiltration
Pharmacokinetics
- well absorbed orally
- well distributed to tissues, including CSF & eye
- eliminated largely in the urine unchanged
- elimination 1/2life is 6 hours (75-200 hours ESRD)
elimination via kidney
protein binding = 2-4 %
1/2life = 3-8 hours
elimination by hemodialysis = +
Monitor
- therapeutic monitoring:
- doses adjusted by laboratory parameters of hepatotoxicity, nephrotoxicity & myelotoxicity without measuring blood levels
Adverse effects
- most common (1-10%)
- uncommon (< 1%)
Drug interactions
- cytarabine antagonizes the effects of flucytosine
- amphotericin B in combination may increase flucytosine, increasing toxicity
- antacids in combination decrease flucytosine activity; take 2 hours apart
Mechanism of action
- deaminated by fungal cytosine deaminase to 5-fluorouracil which is fungicidal
More general terms
Additional terms
References
- ↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- ↑ Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998