Desoximetasone Ointment

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

Desoximetasone Ointment contains NLT 90.0% and NMT 110.0% of the labeled amount of desoximetasone (C₂₂H₂₉FO₄).

2 IDENTIFICATION

A. The retention time of the desoximetasone peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 PROCEDURE

Mobile phase: Methanol, glacial acetic acid, and water (65:1:35)

Diluent: Methanol and spectrophotometric acetonitrile saturated with n-heptane (1:1)

Standard stock solution: 0.4 mg/ml. of USP Desoximetasone RS in methanol

Standard solution: 0.04 mg/mL of USP Desoximetasone RS from the Standard stock solution in Diluent

Sample solution: Nominally 0.04 mg/mL of desoximetasone in Diluent prepared as follows. Transfer an amount of Ointment nominally equivalent to 2 mg of desoximetasone to a 50-mL centrifuge tube. Add 20 mL of n-heptane that has been previously saturated with spectrophotometric acetonitrile, and heat gently with occasional shaking until the Ointment is completely dispersed. Allow to cool slightly, and extract with a 10-mL portion of spectrophotometric acetonitrile. Shake vigorously, centrifuge, remove the bottom layer of spectrophotometric acetonitrile with a syringe and needle, and transfer to a 50-mL volumetric flask. Using the same needle and syringe, extract the desoximetasone with successive 10- and 8-mL portions of spectrophotometric acetonitrile, combining all spectrophotometric acetonitrile layers in the 50-mL flask. Dilute with methanol nearly to volume, and allow the solution to reach room temperature. Dilute with methanol to volume.

3.1.1 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm x 15-cm; packing 17

Flow rate: 1 mL/min

Injection volume: 10 µL

3.2 System suitability

Sample: Standard solution

3.2.1 Suitability requirements

Resolution: NLT 5.0 between the desoximetasone and solvent peaks

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

3.2.2 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of desoximetasone (C₂₂H₂₉FO₄) in the portion of Ointment taken:

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

r_U = peak response of desoximetasone from the Sample solution

r_S = peak response of desoximetasone from the Standard solution

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

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

Acceptance criteria: 90.0%-110.0%

4 PERFORMANCE TESTS

MINIMUM FILL (755): Meets the requirements

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in collapsible tubes at controlled room temperature.

USP REFERENCE STANDARDS (11)

USP Desoximetasone RS