Clindamycin Phosphate

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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C₁₈H₃₄ClN₂O₈PS        504.96 

l-threo-α-d-galacto-Octopyranoside, methyl 7-chloro-6,7,8-trideoxy-6-[[(1-methyl-4-propyl-2-pyrrolidinyl)carbonyl]amino]-1-thio-, 2-(dihydrogen phosphate), (2S-trans)-; 

Methyl 7-chloro-6,7,8-trideoxy-6-(1-methyl-trans-4-propyl-l-2-pyrrolidinecarboxamido)-1-thio-l-threo-α-d-galacto-octopyranoside 2-(dihydrogen 

phosphate) CAS RN®: 24729-96-2; UNII: EH6D7113I8. 

1 DEFINITION 

Clindamycin Phosphate has a potency equivalent to NLT 758 µg/mg of clindamycin (C₁₈H₃₃ClN₂O₅S), calculated on the anhydrous basis.

2 IDENTIFICATION 

Change to read: 

A.Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K

Standard: Add 0.2 mL of water to 50 mg of USP Clindamycin Phosphate RS, and heat to dissolve. Evaporate to dryness under vacuum, and dry the residue at 100°–105° for 2 h. 

Sample: Add 0.2 mL of water to 50 mg of Clindamycin Phosphate, and heat to dissolve. Evaporate to dryness under vacuum, and dry the residue at 100°–105° for 2 h. 

Acceptance criteria: Meets the requirements 

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 

Solution A: Add 14 mL of phosphoric acid to 4000 mL of water. Add 10 mL of ammonium hydroxide, and adjust with ammonium hydroxide to a pH of 5.6 ± 0.1. 

Solution B: Acetonitrile and methanol (900:100) 

Solution C: Solution B and Solution A (80:920) 

Solution D: Solution B and Solution A (480:520) 

Diluent: Solution B and Solution A (20:80) 

Mobile phase: See Table 1. 

Table 1 

System suitability solution: 2.2 mg/mL of USP Clindamycin Phosphate System Suitability RS in Diluent. Shake, and sonicate to dissolve. Standard solution: 2.2 mg/mL of USP Clindamycin Phosphate RS in Diluent. Shake, and sonicate to dissolve. Sample solution: 2.2 mg/mL of Clindamycin Phosphate in Diluent. Shake, and sonicate to dissolve. Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 214 nm 

Column: 4.6-mm × 25-cm; 5-µm packing L7 

Column temperature: 40° 

Flow rate: 1.2 mL/min 

Injection volume: 20 µL 

System suitability 

Samples: System suitability solution and Standard solution 

Suitability requirements 

Resolution: NLT 3.0 between clindamycin phosphate and 7-epiclindamycin phosphate, System suitability solution Tailing factor: NMT 2.0 for clindamycin phosphate, Standard solution 

Relative standard deviation: NMT 0.73%, Standard solution 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the quantity of clindamycin (C₁₈H₃₃ClN₂O₅S), in µg/mg, in the portion of Clindamycin Phosphate taken: 

Acceptance criteria: NLT 758 µg/mg on the anhydrous basis 

4 IMPURITIES 

Organic Impurities 

Solution A, Solution B, Solution C, Solution D, Diluent, Mobile phase, System suitability solution, Sample solution, and Chromatographic system: Proceed as directed in the Assay. 

Standard solution: 14 µg/mL of USP Clindamycin Phosphate RS in Diluent. Shake, and sonicate to dissolve. System suitability 

Samples: System suitability solution and Standard solution 

Suitability requirements 

Resolution: NLT 3.0 between 7-epiclindamycin phosphate and clindamycin phosphate, System suitability solution Tailing factor: NMT 2.0 for clindamycin phosphate, Standard solution 

Relative standard deviation: NMT 5.0% for clindamycin phosphate, Standard solution 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of each impurity in the portion of Clindamycin Phosphate taken: 

Result = (r_U/r_S) × (C_S/C_U) × P × (F₁/F₂ ) × 100 

r_U = peak response of each impurity from the Sample solution 

r_S = peak response of clindamycin phosphate from the Standard solution 

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

C_U = concentration of Clindamycin Phosphate, corrected for water content, in the Sample solution (mg/mL) U 

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

F₁ = conversion factor, 0.001 mg/µg 

F₂ = relative response factor (see Table 2) 

Acceptance criteria: See Table 2. The reporting level is 0.05%. 

Table 2 

^a Methyl 6,8-dideoxy-6-[(2S,4R)-1-methyl-4-propylpyrrolidine-2-carboxamido]-1-thio-d-erythro-α-d-galacto-octopyranoside 2-phosphate.

^b Methyl 6,8-dideoxy-6-[(2S,4R)-1-methyl-4-propylpyrrolidine-2-carboxamido]-1-thio-d-erythro-α-d-galacto-octopyranoside.

^c Methyl 7-chloro-6,7,8-trideoxy-6-[(2S,4R)-1-methyl-4-ethylpyrrolidine-2-carboxamido]-1-thio-l-threo-α-d-galacto-octopyranoside 2- phosphate. 

^d Methyl 7-chloro-6,7,8-trideoxy-6-[(2S,4R)-1-methyl-4-propylpyrrolidine-2-carboxamido]-1-thio-d-erythro-α-d-galacto-octopyranoside 2- phosphate. 

^e Methyl 7-chloro-6,7,8-trideoxy-6-[(2S,4R)-1-methyl-4-propylpyrrolidine-2-carboxamido]-1-thio-l-threo-α-d-galacto-octopyranoside 3- phosphate. 

^f Methyl 7-chloro-6,7,8-trideoxy-6-[(2S,4R)-1-methyl-4-propylpyrrolidine-2-carboxamido]-1-thio-L-threo-α-d-galacto-octopyranoside. 

5 SPECIFIC TESTS 

Crystallinity 〈695〉: Meets the requirements 

pH 〈791〉 

Sample solution: 10 mg/mL 

Acceptance criteria: 3.5–4.5 

Water Determination 〈921〉, Method I: NMT 6.0% 

Sterility Tests 〈71〉 

Sample solution: 6 g of specimen aseptically dissolved in 200 mL of Fluid A 

Analysis: Test as directed in the Test for Sterility of the Product to Be Examined, Membrane Filtration. 

Acceptance criteria: It meets the requirements where the label states that it is sterile or must be subjected to further processing during the preparation of injectable dosage forms. 

Bacterial Endotoxins Test 〈85〉: It contains NMT 0.58 USP Endotoxin Units/mg of clindamycin, where the label states that Clindamycin Phosphate is sterile or must be subjected to further processing during the preparation of injectable dosage forms. 

6 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in tight containers, and store below 30°. 

Labeling: Where it is intended for use in preparing injectable dosage forms, the label states that it is sterile or must be subjected to further processing during the preparation of injectable dosage forms. 

USP Reference Standards 〈11〉 

USP Clindamycin Phosphate RS 

USP Clindamycin Phosphate System Suitability RS 

Contains clindamycin phosphate and the following impurity: 

7-Epiclindamycin phosphate; 

Methyl 7-chloro-6,7,8-trideoxy-6-[(2S,4R)-1-methyl-4-propylpyrrolidine-2-carboxamido]-1-thio-d-erythro-α-d-galacto-octopyranoside 2-phosphate. C₁₈H₃₄ClN₂O₈PS 504.96