5-Flucytosine, Serum
Use
Flucytosine is a broad-spectrum antifungal agent generally used in combined therapy (often with amphotericin B) for treatment of fungal infections such as cryptococcal meningitis. It is important for monitoring serum concentration during therapy to evaluate potential toxicity and patient compliance. Concerns with toxicity (ie, bone marrow suppression, hepatic dysfunction) and development of fungal resistance limit the use of flucytosine, particularly as a monotherapy. This test helps ensure that serum concentrations do not accumulate to excessive levels, especially in patients with kidney dysfunction or when using nephrotoxic agents like amphotericin B.
Special Instructions
Serum samples must be collected following specific instructions based on the administration method: 1 to 2 hours after oral dose, 1 hour after intramuscular dose, or 30 minutes after intravenous infusion. The specimen must be centrifuged and aliquoted into a plastic vial within 2 hours of collection. Proper specimen handling is crucial as the test cannot be performed on whole blood and serum must be separated from cells promptly.
Limitations
This test cannot be performed on whole blood; it requires serum separated from cells. Specimens should be handled correctly to avoid rejection due to improper type or handling. The test's effective use depends on adherence to timing instructions for collecting peak or trough levels based on the administration method. Specimen stability and transportation conditions must be strictly followed.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 3639-2
- 3639-2
Result Turnaround Time
3-8 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
0.5 mL
Minimum Volume
0.3 mL
Container
Red top (preferred), plastic vial (submission container)
Collection Instructions
For peak level, collect 1-2 hours after oral dose, 1 hour after intramuscular dose, or 30 minutes after intravenous infusion. Trough specimens should be collected immediately prior to next scheduled dose. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 28 days |
| Refrigerated | 28 days |
| Frozen | 28 days |