Rimexolone

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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C₂₄H₃₄O₃ 370.52

Androsta-1,4-diene-3-one, 11-hydroxy-16,17-dimethyl-17-(1-oxopropyl)-, (11β,16α,17β)-;

11β-Hydroxy-16α,17α-dimethyl-17-propionylandrosta-1,4-diene-3-one CAS RN^®: 49697-38-3; UNII: O7M2E4264D.

1 DEFINITION

Rimexolone contains NLT 97.0% and NMT 102.0% of rimexolone (C₂₄H₃₄O₃), calculated on the dried basis.

2 IDENTIFICATION

2.1 A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K

2.2 B. Thin-Layer Chromatography

Standard solution: 10 mg/mL of USP Rimexolone RS in chloroform

Sample solution: 10 mg/mL of rimexolone in chloroform

Chromatographic system

(See Chromatography 〈621〉, Thin-Layer Chromatography.)

Adsorbent: 0.25-mm layer of silica gel mixture

Application volume: 5 µL

Developing solvent system: Chloroform and methanol (19:1)

Analysis

Samples: Standard solution and Sample solution

Apply the samples to the thin-layer chromatographic plate. Develop the chromatogram in the Developing solvent system until the solvent front has moved about three-fourths of the length of the plate. Observe the plate under short-wavelength UV light.

Acceptance criteria: The Rf value of the principal spot of the Sample solution corresponds to that of the principal spot of the Standard solution.

3 ASSAY

3.1 Procedure

Mobile phase: Acetonitrile and water (6:4)

Standard solution: 0.2 mg/mL of USP Rimexolone RS, prepared by dissolving a suitable quantity in methanol and diluting with Mobile phase to volume

Sample stock solution: 1 mg/mL of Rimexolone in methanol

Sample solution: 0.2 mg/mL of Rimexolone diluted with Mobile phase from the Sample stock solution

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 242 nm

Column: 4.6-mm × 25-cm; packing L1

Flow rate: 1 mL/min

Injection volume: 20 µL

System suitability

Sample: Standard solution

Suitability requirements

Capacity factor, k′: NLT 1.5

Column efficiency: NLT 3000 theoretical plates

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of rimexolone (C₂₄H₃₄O₃) in the portion of Rimexolone 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 Rimexolone RS in the Standard solution (mg/mL)

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

Acceptance criteria: 97.0%–102.0% on the dried basis

4 IMPURITIES

4.1 Residue on Ignition 〈281〉: NMT 0.1%

4.2 Organic Impurities

Mobile phase: Prepare as directed in the Assay.

Standard solution: Use the Standard solution prepared in the Assay.

Sample stock solution: 1 mg/mL of Rimexolone in methanol

Sample solution: 0.2 mg/mL of Rimexolone in Mobile phase from the Sample stock solution

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 242 nm

Column: 4.6-mm × 25-cm; packing L1

Flow rate: 1 mL/min

Injection volume: 20 µL

System suitability

Sample: Standard solution

Suitability requirements

Capacity factor, k′: NLT 1.5

Column efficiency: NLT 3000 theoretical plates

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

Analysis

Sample: Sample solution

Calculate the percentage of each impurity in the portion of Rimexolone taken:

Result = (r_U/r_T) × 100

r_U = peak response for each impurity

r_T = sum of all the peak responses

Acceptance criteria

Individual impurities: NMT 1.0%

Total impurities: NMT 2.0%

5 SPECIFIC TESTS

5.1 Optical Rotation, Specific Rotation 〈781S〉

Sample solution: 20 mg/mL in chloroform

Acceptance criteria: +47° to +54°

5.2 Loss on Drying 〈731〉

Analysis: Dry a sample under vacuum at 105° for 3 h.

Acceptance criteria: NMT 1.0%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Rimexolone RS (USP 1-Dec-2024)