Clindamycin Phosphate Vaginal Inserts

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 Inserts contain the equivalent of NLT 90.0% and NMT 110.0% of the labeled amount of clindamycin (C₁₈H₃₃ClN₂O₅S). 

2 IDENTIFICATION 

Change to read: 

 A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197MSample: Transfer a Vaginal Insert into a suitable container, add 120 mL of methylene chloride, insert a stopper, and shake until the Vaginal Insert is completely dissolved. Using a vacuum, pass through a methylene chloride-compatible filter having a 0.45-µm pore size. Rinse the filter with several portions of methylene chloride, and allow the filter to air-dry. Use the white residue to prepare the Mineral oil dispersion for the test. 

Acceptance criteria: The IR absorption of the Sample exhibits maxima at the same wavelengths as that of a similar preparation of USP Clindamycin Phosphate RS. 

 B. 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 

 Procedure 

Buffer: 10.54 g/L of monobasic potassium phosphate in water. Adjust with phosphoric acid to a pH of 2.5. 

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: 0.24 mg/mL of USP Clindamycin Phosphate RS and 6 µg/mL of USP Clindamycin Hydrochloride RS, in Buffer Standard solution: 0.24 mg/mL of USP Clindamycin Phosphate RS in Buffer 

Sample solution: Transfer 1 Vaginal Insert to a suitable 100-mL container. Add 40 mL of isooctane, and seal the container tightly with a teflon-lined septum and crimp cap. Shake vigorously for about 15 min until all of the Vaginal Insert is dissolved. Add 40.0 mL of Buffer. Recap the container tightly, and shake vigorously for NLT 30 min, taking care to avoid leakage. Allow the layers to separate, and remove a volume of the lower aqueous layer sufficient to perform the following steps. Pass the aqueous solution through a filter having a 5-µm or finer pore size, discarding the first 2 mL of the filtrate. Collect the remaining filtrate, and prepare a solution equivalent to 0.2 mg/mL of clindamycin with Buffer. 

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: 35 µL 

System suitability 

Samples: System suitability solution and Standard solution 

Suitability requirements 

Resolution: NLT 2.0 between clindamycin phosphate and clindamycin hydrochloride, System suitability solution Calculate as follows. 

Result = [(t₂ − t₁ )/(w_h1 + w_h2 )] × 1.177 

t₂ = retention time of the second peak 

t₁ = retention time of the first peak 

w_h1 = height at half width of the first peak 

w_h2 = height at half width of the second peak 

Relative standard deviation: NMT 2.5%, Standard solution 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of clindamycin (C H ClN O S) equivalent in the Vaginal Insert taken: 18

Result = (r_U/r_S) × (C_S/C_U) × 100 

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

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

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

F = conversion factor, 0.001 mg/µg 

Acceptance criteria: 90.0%–110.0%. Use as the Assay value the average of the determinations obtained in the test for Uniformity of Dosage Units 〈905〉, Content Uniformity. 

4 PERFORMANCE TESTS 

 Uniformity of Dosage Units 〈905〉: Meet the requirements 

5 ADDITIONAL REQUIREMENTS 

 Packaging and Storage: Preserve in well-closed containers, at controlled room temperature, or in a cool place. 

 USP Reference Standards 〈11〉 

USP Clindamycin Hydrochloride RS 

USP Clindamycin Phosphate RS