Cloxacillin Sodium for Oral Solution

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

Cloxacillin Sodium for Oral Solution is a dry mixture of Cloxacillin Sodium and one or more suitable buffers, colors, flavors, and preservatives. It contains the equivalent of NLT 90.0% and NMT 120.0% of the labeled amount of cloxacillin (C₁₉H₁₈CIN₃O₅S).

2 ASSAY

2.1 PROCEDURE

Buffer: 0.02 M of monobasic potassium phosphate in water, adjusted with 2 N sodium hydroxide to a pH of 6.8

Mobile phase: Acetonitrile and Buffer (20:80)

Standard solution: 0.55 mg/mL of USP Cloxacillin Sodium RS in Buffer

Sample solution: Nominally 0.5 mg/mL of cloxacillin in Buffer, prepared as follows. Constitute Cloxacillin Sodium for Oral Solution as directed in the labeling. Transfer a suitable portion of the resulting solution to a volumetric flask, dilute with Buffer to volume, mix, and stir for 15 min. Pass a portion of the solution through a suitable filter, discarding the first 5 mL of the filtrate. Use the clear filtrate.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 225 nm

Column: 4.6-mm x 25-cm; packing L1

Flow rate: 1 mL/min

Injection volume: 20 µL

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 1.8

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of cloxacillin (C₁₉H₁₈CIN₃O₅S) in the portion of Cloxacillin Sodium for Oral Solution taken:

Result = (r_u/r_s) × (C_s/C_u) × P × F × 100

r_u = peak response from the Sample solution

r_s = peak response from the Standard solution

C_s = concentration of USP Cloxacillin Sodium RS in the Standard solution (mg/mL)

C_u = nominal concentration of cloxacillin in the Sample solution (mg/mL)

P = potency of cloxacillin in USP Cloxacillin Sodium RS (µg/mg)

F = conversion factor, 0.001 mg/µg

Acceptance criteria: 90.0%-120.0%

3 PERFORMANCE TESTS

3.1 DELIVERABLE VOLUME (698): Meets the requirements

3.2 UNIFORMITY OF DOSAGE UNITS (905)

For solids packaged in single-unit containers

4 SPECIFIC TESTS

4.1 PH (791).

Sample solution: Constitute as directed in the labeling.

Acceptance criteria: 5.0-7.5

4.2 WATER DETERMINATION (921), Method /: NMT 1.0%

5 ADDITIONAL REQUIREMENTS

5.1 PACKAGING AND STORAGE: Preserve in tight containers.

5.2 USP REFERENCE STANDARDS (11)

USP Cloxacillin Sodium RS