Flucytosine Compounded Oral Suspension

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Flucytosine Compounded Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of flucytosine (C₄H₄FN₃O). 

Prepare Flucytosine Compounded Oral Suspension 10 mg/mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

Empty the contents of the required number of capsules into a suitable mortar, or add Flucytosine powder to the mortar. Add 10 mL of Vehicle, and mix to a uniform paste. Add Vehicle in small portions almost to volume, and mix thoroughly after each addition. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add enough Vehicle to bring to nal volume, and mix well.

2 ASSAY

Procedure

Solution A: 1 g of ammonium acetate and 1 mL of diisopropylamine in 1 L of water. Adjust with glacial acetic acid to a pH of 7.5. Mobile phase: Methanol and Solution A (50:50). Filter, and degas.

Standard solution: 50 µg/mL of USP Flucytosine RS in Mobile phase

Sample solution: Agitate the container of Oral Suspension for 30 min on a rotating mixer, remove a 5-mL sample, and store in a clear glass vial at −70° until analyzed. At the time of analysis, remove the sample from the freezer, allow it to reach room temperature, and mix on a vortex mixer for 30 s. Pipet 0.5 mL of the sample into a 100-mL volumetric ask, and dilute with Mobile phase to volume.

2.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 280 nm

Column: 4.6-mm × 200-mm; 5-µm packing L3

Flow rate: 1 mL/min

Injection volume: 20 µL

2.2 System suitability

Sample: Standard solution

[Note—The retention time for flucytosine is about 3 min.]

Suitability requirements

Relative standard deviation: NMT 1.0% for replicate injections

3 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of flucytosine (C₄H₄FN₃O) in the portion of Oral Suspension taken:

Result = (r_U /r_S ) × (C_S /C_U) × 100

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

C_S = concentration of USP Flucytosine RS in the Standard solution (µg/mL)

C_U = nominal concentration of flucytosine in the Sample solution (µg/mL)

Acceptance criteria: 90.0%–110.0%

4 SPECIFIC TESTS

pH 〈791〉: 4.0–5.0

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Package in tight, light-resistant containers. Store in a refrigerator.

Beyond-Use Date: NMT 60 days after the date on which it was compounded when stored in a refrigerator

Labeling: Label it to state that it is to be well shaken, and to state the Beyond-Use Date.

USP Reference Standards 〈11〉

USP Flucytosine RS.