Mefenamic Acid

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

Mefenamic acid contains NLT 98.0% and NMT 102.0% of mefenamic acid (C₁₅H₁₅NO₂), calculated on the dried basis.

2 IDENTIFICATION

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K or 197A (CN 1-May-2020)

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

3 ASSAY

Procedure

Buffer: 50 mM monobasic ammonium phosphate. Adjust with 3 M ammonium hydroxide to a pH of 5.0.

Mobile phase: Acetonitrile, tetrahydrofuran, and Buffer (23:7:20)

Standard solution: 0.2 mg/mL of USP Mefenamic Acid RS in Mobile phase

Sample solution: 0.2 mg/mL of Mefenamic Acid in Mobile phase

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm × 25-cm; 5-μm packing L1

Flow rate: 1 mL/min

Injection volume: 10 μL

System suitability

Sample: Standard solution

Suitability requirements

Column efficiency: NLT 8200 theoretical plates

Tailing factor: NMT 1.6

Relative standard deviation: NMT 0.73%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of mefenamic acid (C₁₅H₁₅NO₂) in the portion of Mefenamic Acid taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of mefenamic acid from the Sample solution

r_S = peak response of mefenamic acid from the Standard solution

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

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

Acceptance criteria: 98.0%–102.0% on the dried basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Organic Impurities

Buffer, Mobile phase, and Chromatographic system: Proceed as directed in the Assay.

Standard solution: 0.01 mg/mL of USP Mefenamic Acid RS in Mobile phase

Sensitivity solution: 0.3 μg/mL of USP Mefenamic Acid RS in Mobile phase from the Standard solution

Sample solution: 1 mg/mL of Mefenamic Acid in Mobile phase

System suitability

Samples: Standard solution and Sensitivity solution

Suitability requirements

Tailing factor: NMT 1.6, Standard solution

Relative standard deviation: NMT 5.0%, Standard solution

Signal-to-noise ratio: NLT 10, Sensitivity solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each impurity in the portion of Mefenamic Acid taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of each impurity from the Sample solution

r_S = peak response of mefenamic acid from the Standard solution

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

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

Acceptance criteria: The reporting threshold is 0.03%.

Any impurity: NMT 0.07%

Total impurities: NMT 0.5%

5 SPECIFIC TESTS

Loss on Drying 〈731〉

Analysis: Dry at 105° for 4 h.

Acceptance criteria: NMT 1.0%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers.

USP Reference Standards 〈11〉

USP Mefenamic Acid RS