Mefenamic Acid Capsules

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 Capsules contain NLT 90.0% and NMT 110.0% of the labeled amount of mefenamic acid (C₁₅H₁₅NO₂).

2 IDENTIFICATION

A. The UV spectrum of the mefenamic acid peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

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

Solution A: 50 mM solution of monobasic ammonium phosphate in water. Adjust with 3 M ammonium hydroxide to a pH of 5.0.

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

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

Sample solution: Nominally 0.2 mg/mL of mefenamic acid in Mobile phase prepared as follows. Transfer a suitable amount of mefenamic acid from the contents of NLT 20 Capsules to an adequate volumetric flask. Add 2% of final volume of tetrahydrofuran, and sonicate for about 5 min with occasional mixing. Dilute with Mobile phase to the final volume.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 254 nm. For Identi

cation A, use a diode array detector in the range of 200–400 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 1.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of mefenamic acid (C₁₅H₁₅NO₂) in the portion of Capsules 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 = nominal concentration of mefenamic acid in the Sample solution (mg/mL)

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Change to read:

Dissolution 〈711〉

0.05 M tris buffer: Dissolve 60.5 g of tris(hydroxymethyl)aminomethane in 6 L of water, and dilute with water to 10 L. Adjust with phosphoric acid to a pH of 9.0 ± 0.05. To a second container, transfer about 6 L of this solution, add 100 g of sodium lauryl sulfate, and mix to dissolve the solid material. Transfer this solution back into the first container, and mix.

Medium: 0.05 M tris buffer; 900 mL

Apparatus 1: 100 rpm

Time: 45 min

Solution A, Mobile phase, Standard solution, (ERR 1-Dec-2019) Chromatographic system, and System suitability: Proceed as directed in the Assay, making any necessary volumetric adjustments.

Sample solution: Take a portion of the solution under test, and dilute if necessary. (ERR 1-Dec-2019)

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of mefenamic acid (C₁₅H₁₅NO) dissolved:

Result = (r_U/r_S) × C_S × V × D × (1/L) × 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)

V = volume of Medium, 900 mL

D = dilution factor for the Sample solution

L = label claim (mg/Capsule)

Tolerances: NLT 75% (Q) of the labeled amount of mefenamic acid (C₁₅H₁₅NO) is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 IMPURITIES

Organic Impurities

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

System suitability solution: 0.01 mg/mL of USP 2,3-Dimethylaniline RS and 1 mg/mL of USP Mefenamic Acid RS in Mobile phase

Sensitivity solution: 0.5 μg/mL of USP Mefenamic Acid RS in Mobile phase

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

Sample solution: Nominally 1 mg/mL of mefenamic acid in Mobile phase from the contents of NLT 20 Capsules. Sonicate to dissolve if necessary.

System suitability

Samples: System suitability solution, Sensitivity solution, and Standard solution

Suitability requirements

Resolution: NLT 2 between 2,3-dimethylaniline and mefenamic acid, System suitability solution

Relative standard deviation: NMT 1.0%, Standard solution

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

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of any individual degradation product in the portion of Capsules taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of any individual degradation product 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 = nominal concentration of mefenamic acid in the Sample solution (mg/mL)

Acceptance criteria: See Table 1. The reporting threshold is 0.05%.

Table 1

^a This is a process impurity and is not included in the total degradation products.

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers. Store at 20°–25°, excursions permitted between 15° and 30°.

USP Reference Standards 〈11〉

USP 2,3-Dimethylaniline RS

2,3-Dimethylaniline.