Dicloxacillin Sodium 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 

Dicloxacillin Sodium Capsules contain NLT 90.0% and NMT 120.0% of the labeled amount of dicloxacillin (C₁₉H₁₇Cl₂N₃O₅S).

2 IDENTIFICATION 

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

3 ASSAY 

3.1 Procedure 

Buffer: 2.72 g/L of monobasic potassium phosphate in water, adjusted with 8 N potassium hydroxide to a pH of 5.0 ± 0.1 Mobile phase: Acetonitrile and Buffer (50:150) 

Standard solution: 1.1 mg/mL of USP Dicloxacillin Sodium RS in Buffer. Use the Standard solution promptly, or refrigerate and use on the day prepared. 

Sample solution: Nominally 1 mg/mL of dicloxacillin in Buffer, prepared as follows. Remove, as completely as possible, the contents of NLT 10 Capsules. Transfer a suitable portion of the powder to a volumetric ask, dilute with Buffer to volume, and mix for 10 min with the aid of a magnetic stirrer. Pass a portion of the solution through a suitable lter, discarding the rst 5 mL of the ltrate. Use the clear ltrate. Use the Sample solution promptly, or refrigerate and use on the day prepared. 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 225 nm 

Column: 4.6-mm × 25-cm; packing L1 

Flow rate: 2 mL/min 

Injection volume: 10 µL 

System suitability 

Sample: Standard solution 

Suitability requirements 

Column eciency: NLT 700 theoretical plates 

Tailing factor: NMT 2.0 

Capacity factor: 4–11 

Relative standard deviation: NMT 2.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of dicloxacillin (C₁₉H₁₇Cl₂N₃O₅S) in the portion of Capsules taken: 

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

r_u = peak area from the Sample solution 

r_s = peak area from the Standard solution 

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

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

P = potency of dicloxacillin in USP Dicloxacillin Sodium RS (µg/mg) 

F = conversion factor, 0.001 mg/µg 

Acceptance criteria: 90.0%–120.0% 

4 PERFORMANCE TESTS 

Change to read: 

4.1 Dissolution 〈711〉 

Medium: Water; 900 mL 

Apparatus 1: 100 rpm 

Time: 30 min 

Standard solution: USP Dicloxacillin Sodium RS in Medium 

Sample solution: Sample per the chapter. Pass a portion of the solution under test through a suitable lter. (ERR 1-Mar-2020) Dilute with Medium to a concentration that is similar to the Standard solution. 

Instrumental conditions 

Mode: UV-Vis▲ (ERR 1-Mar-2020) 

Tolerances: NLT 75% (Q) of the labeled amount of dicloxacillin (C₁₉H₁₇Cl₂N₃O₅S) is dissolved. 

4.2 Uniformity of Dosage Units 〈905〉: Meet the requirements 

5 SPECIFIC TESTS 

Water Determination 〈921〉, Method I: NMT 5.0% 

6 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in tight containers. 

USP Reference Standards 〈11〉 

USP Dicloxacillin Sodium RS