Clindamycin Phosphate Vaginal Cream

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 Vaginal Cream contains an amount of clindamycin phosphate equivalent to NLT 90.0% and NMT 110.0% of the labeled amount of clindamycin (C₁₈H₃₃ClN₂O₅S).

2 IDENTIFICATION

 A. The relative retention time of the major peak for clindamycin phosphate 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, and mix.

System suitability solution: 0.6 mg/mL each of USP Clindamy cin Phosphate RS and USP Clindamy cin Hy drochloride RS in Mobile phase

Standard solution: 0.25 mg/mL of USP Clindamycin Phosphate RS in Mobile phase

Sample solution: Nominally 0.2 mg/mL of clindamycin in Mobile phase from Cream, prepared as follows. Transfer a suitable portion of Cream to a stoppered conical flask, and add Mobile phase. Add about 10 glass beads (about 10 mm in diameter). Insert the stopper securely in the flask, and shake by mechanical means at 50° for 1 h. Cool in an ice bath for 20 min, and centrifuge. Pass a portion of the cloudy lower layer through a filter of 2-µm or finer pore size, and use the filtrate.

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 clindamycin phosphate and clindamycin, System suitability solution Column efficiency: NLT 1700 theoretical plates, System suitability solution

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 Cream 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 Clindamycin Phosphate RS (µg/mg)

F = conversion factor, 0.001 mg/µg

Acceptance criteria: 90.0%–110.0%

4 SPECIFIC TESTS

PH 〈791〉: 3.0–6.0, determined on the undiluted Cream

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in well-closed containers.

USP REFERENCE STANDARDS 〈11〉

USP Clindamycin Hydrochloride RS USP Clindamycin Phosphate RS