Leflunomide 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

Leflunomide Compounded Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of leflunomide (C₁₂H₉F₃N₂O₂).

Prepare Lefllunomide Compounded Oral Suspension 20 mg/mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

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Place the Leflunomide powder in a suitable container and triturate to a fine powder. Add a small amount of Vehicle and mix well to form a smooth paste. Add a sufficient amount of Vehicle to make the contents pourable. Transfer the contents stepwise and quantitatively to a calibrated container using the remainder of the Vehicle. Add sufficient Vehicle to bring to final volume. Mix well.

[Caution—Leflunomide is a hazardous drug and must be handled accordingly.]

2 ASSAY

Procedure

Mobile phase: Add 350 mL of acetonitrile to 650 mL of water. Add 5 mL of trimethylamine and adjust with phosphoric acid to a pH of 4.0.

Standard solution: 0.5 mg/mL of USP Le flunomide RS in methanol

Sample solution: Transfer 0.625 mL of Oral Suspension into a 25-mL volumetric flask, and add methanol to volume. Pass through a filter of

0.22-μm pore size.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 260 nm

Column: 2.1-mm × 5-cm; 1.6-μm packing L1

Temperatures

Autosampler: 10°

Column: 20°

Flow rate: 0.39 mL/min

Injection volume: 1 μL

System suitability

Sample: Standard solution

[Note—The retention time for leflunomide is about 8.6 min.]

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0% for replicate injections

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of leflunomide (C₁₂H₉F₃N₂O₂) in the portion of Oral Suspension taken:

Result = (r_U/r_S)x(C_S/C_U) × 100

r_U = peak response of leflunomide from the Sample solution

r_S = peak response of leflunomide from the Standard solution

C_S = concentration of USP Leflunomide RS in the Standard solution (mg/mL)

C_U = nominal concentration of leflunomide in the Sample solution (mg/mL)

Acceptance criteria: 90.0%–110.0%

3 SPECIFIC TESTS

pH 〈791〉: 3.7–4.7

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Package in tight, light-resistant containers. Store at controlled room temperature or in a refrigerator.

Beyond-Use Date: NMT 90 days after the date on which it was compounded when stored at controlled room temperature or in a refrigerator

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

USP Reference Standards 〈11〉

USP Leflunomide RS

2S (USP41)