Clindamycin Phosphate Topical 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

Clindamycin Phosphate Topical Suspension contains the equivalent of NLT 90.0% and NMT 110.0% of the labeled amount of clindamycin (C₁₈H₃₃ClN₂O₅S).

2 IDENTIFICATION

A. 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

3.1 PROCEDURE

Mobile phase: Dissolve 10.54 g of monobasic potassium phosphate in 775 mL of water, and adjust with phosphoric acid to a pH of 2.5. Add 225 mL of acetonitrile, mix, and filter.

System suitability solution: 0.6 mg/mL each of USP Clindamycin Phosphate RS and USP Clindamycin Hydrochloride RS, in the Mobile phase Standard solution: 0.25 mg/mL of USP Clindamy cin Phosphate RS in the Mobile phase

Sample solution: Equivalent to 0.2 mg/mL of clindamycin from Topical Suspension in Mobile phase. Prepare as follows. Using a suitable hypodermic needle and syringe, transfer a suitable aliquot of Topical Suspension to a suitable volumetric flask, dilute with Mobile phase to volume, and mix.

3.1.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.) Mode: LC

Detector: UV 210 nm

Column: 4.6-mm × 25-cm; packing L7 Flow rate: 1 mL/min

Injection volume: 20 µL

3.1.2 System suitability

Samples: System suitability solution and Standard solution

[NOTE—The relative retention times for clindamycin phosphate and clindamycin are about 1.0 and 1.5, respectively.]

Suitability requirements

Resolution: NLT 6.0 between the clindamycin phosphate and clindamycin peaks, System suitability solution

Column efficiency: NLT 1700 theoretical plates, System suitability solution, calculated from the peak width at half height Tailing factor: NMT 1.3, System suitability solution

Relative standard deviation: NMT 2.5%, Standard solution

3.1.3 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of clindamycin (C₁₈H₃₃ClN₂O₅S) in the portion of the Topical Suspension 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 Clindamy cin Phosphate RS in the Standard solution (mg/mL)

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

P = potency of clindamycin in USP Clindamy cin Phosphate RS (µg/mg)

F = conversion factor, 0.001 mg/µg Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

MINIMUM FILL 〈755〉: Meets the requirements

5 SPECIFIC TESTS

PH 〈791〉: 4.5–6.5

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers.

USP REFERENCE STANDARDS 〈11〉

USP Clindamycin Hydrochloride RS USP Clindamycin Phosphate RS