Naproxen 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

Naproxen Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of naproxen (C₁₄H₁₄O₃).

2 IDENTIFICATION

A.

Sample solution: Standard solution and Sample solution (1:1), prepared as directed in the Assay

Analysis: Chromatograph as directed in the Assay.

Acceptance criteria: The chromatogram of the Sample solution exhibits two main peaks corresponding to naproxen and the internal standard.

3 ASSAY

PROCEDURE

Mobile phase: Prepare a mixture of 500 mL of methanol, 500 mL of water, and 2.46 g of anhydrous sodium acetate, and mix until dissolved. Adjust with glacial acetic acid to a pH of 5.8.

Internal standard solution: 1.1 mg/mL of ethylparaben in methanol

Standard stock solution: Transfer about 62.5 mg of USP Naproxen RS, accurately weighed, to a 50-mL volumetric flask, add about 30 mL of methanol, and sonicate to dissolve. Add 5.0 mL of Internal standard solution, dilute with methanol to volume, and mix.

Standard solution: 0.05 mg/mL of USP Naproxen RS and 0.0044 mg/mL of ethylparaben in Mobile phase from Standard stock solution

Sample stock solution: Transfer an accurately measured volume of Oral Suspension, previously well-mixed and free from air bubbles, nominally equivalent to about 125 mg of naproxen, to a 100-ml volumetric flask, using a "to contain" pipet. Rinse the pipet several times with methanol, and add the rinsings to the volumetric flask. Add 10.0 mL of Internal standard solution, dilute with methanol to volume, and mix.

Sample solution: Nominally equivalent to 0.05 mg/mL of naproxen and 0.0044 mg/mL of ethylparaben in Mobile phase from Sample stock solution. Filter if necessary to obtain a clear solution.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 3.9-mm x 30-cm; packing L1

Flow rate: 2 mL/min.

Injection volume: 35 µL

System suitability

Sample: Standard solution

[NOTE-The relative retention times for ethylparaben and naproxen are 0.6 and 1.0, respectively.]

Suitability requirements

Resolution: NLT 3.0 between ethylparaben and naproxen

Tailing factor: NMT 2.0 for the naproxen peak

Relative standard deviation: NMT 1.5%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of naproxen (C₁₄H₁₄O₃) in the portion of Oral Suspension taken:

                         Result = (R_U/R_S) × (C_S/C_U) × 100

R_U = peak response ratio of naproxen to ethylparaben from the Sample solution

R_S = peak response ratio of naproxen to ethylparaben from the Standard solution

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

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

Acceptance criteria: 90.0%-110.0%

4 PERFORMANCE TESTS

DELIVERABLE VOLUME (698): Meets the requirements for oral suspension packaged in multiple-unit containers

UNIFORMITY OF DOSAGE UNITS (905): Meets the requirements for oral suspension packaged in single-unit containers

5 SPECIFIC TESTS

PH (791): 2.2-3.7

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight, light-resistant containers. Store at room temperature.

USP REFERENCE STANDARDS (11)

USP Naproxen RS