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Fluorocytosine

Flucytosine, 5-FC, Ancobon, 5-Fluorocytosine, Flucytosine Level, 5.

Department

Toxicology

Specimen Collection Criteria

Collect: One plain Red-top tube. (Minimum Whole Blood: 2.0 mL, serum 1.0 mL)

Do not use Serum Separator Tubes.
Time of Collection: Peak level, 2 hours post oral dose.

Physician Office/Draw Specimen Preparation

Do not centrifuge. Maintain whole blood in original collection tube at room temperature (20-26°C or 68-78.8°F) prior to transport.

Preparation for Courier Transport

Transport: Whole blood in original collection tube at room temperature (20-26°C or 68-78.8°F). (Minimum: 2.0 mL)

Rejection Criteria

Serum Separator (SST) tubes.

In-Lab Processing

Do not centrifuge specimen. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 3 days
Frozen (-20°C/-4°F or below): 3 months

Laboratory

Royal Oak Toxicology Laboratory

Performed

Sunday – Saturday. Results available within 24 hrs.

Reference Range

30-80 mcg/mL.

Test Methodology

Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS).

This test was developed and its performance characteristics determined by Beaumont Health. It has not been cleared or approved by the FDA. The Laboratory is regulated under CLIA as qualified to perform high-complexity testing. This test is used for clinical purposes and should not be regarded as investigational or for research.

Clinical Utility

Fluorocytosine is a broad-spectrum antifungal agent generally used in combined therapy (often with amphotericin B) for treatment of fungal infections such as cryptococcal meningitis. Concerns with toxicity (bone marrow suppression, hepatic dysfunction) and development of fungal resistance limit the use of fluorocytosine, particularly as a monotherapy.

There is good correlation between serum concentrations of fluorocytosine with both efficacy and risk for toxicity. Because of the drugs short half-life (3-6 hours), therapeutic monitoring is typically performed at peak levels, 1 to 2 hours after an oral dose.

Fluorocytosine is eliminated primarily as unmetabolized drug in urine. Patients with renal dysfunction may require dose adjustments or more frequent monitoring to ensure that serum concentrations do not accumulate to excessive levels. Nephrotoxicity associated with use of amphotericin B can affect elimination of fluorocytosine when the drugs are coadministered.

CPT Codes

80299
LOINC:  3639-2

Contacts

Last Updated

3/11/2024