Chloramphenicol and Polymyxin B Sulfate Ophthalmic Ointment

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 

Chloramphenicol and Polymyxin B Sulfate Ophthalmic Ointment contains NLT 90.0% and NMT 120.0% of the labeled amount of chloramphenicol (C₁₁H₁₂Cl₂N₂O₅) and NLT 90.0% and NMT 125.0% of the labeled amount of polymyxin B. 

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 

Chloramphenicol 

Mobile phase: Methanol, glacial acetic acid, and water (450:1:550) 

Standard stock solution: 0.25 mg/mL of USP Chloramphenicol RS in methanol 

Standard solution: 0.1 mg/mL of USP Chloramphenicol RS from the Standard stock solution in Mobile phase. Pass through a suitable filter, and use the clear filtrate. 

Sample stock solution: Nominally 0.25 mg/mL of chloramphenicol prepared as follows. Transfer a portion of Ophthalmic Ointment containing nominally 25 mg of chloramphenicol to a suitable conical flask. Add 20 mL of cyclohexane, mix, and sonicate for 2 min. Add 60 mL of methanol. Filter this mixture, collecting the filtrate in a 100-mL volumetric flask. Wash the filter with methanol, collecting the washings in the volumetric flask. Dilute with methanol to volume. Transfer 50.0 mL of the resulting solution to a suitable round-bottom flask, and evaporate to dryness by rotating the flask under vacuum in a water bath at 35°. Dissolve the residue in 50.0 mL of methanol. Sample solution: Nominally 0.1 mg/mL of chloramphenicol from the Sample stock solution in Mobile phase. Pass through a suitable filter, and use the clear filtrate. 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 280 nm 

Column: 4.6-mm × 10-cm; 5-µm packing L1 

Flow rate: 1 mL/min 

Injection volume: 10 µL 

System suitability 

Sample: Standard solution 

Suitability requirements 

Tailing factor: NMT 2.0 

Relative standard deviation: NMT 1.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of chloramphenicol (C₁₁H₁₂Cl₂N₂O₅) in the portion of Ophthalmic Ointment taken: 

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

r_U = peak height from the Sample solution 

r_S = peak height from the Standard solution 

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

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

P = potency of chloramphenicol in USP Chloramphenicol RS (µg/mg) 

F = conversion factor, 0.001 mg/µg 

Acceptance criteria: 90.0%–120.0% 

Polymyxin B 

(See Antibiotics—Microbial Assays 〈81〉.) 

Sample solution: Shake a portion of Ophthalmic Ointment containing nominally 5000 Polymyxin B Units with 50 mL of ether in a separator. Extract with four 20-mL portions of Buffer B.6. Combine the aqueous extracts in a 100-mL volumetric flask, and dilute with Buffer B.6 to volume. 

Analysis: Proceed as directed in the chapter. Dilute the Sample solution with Buffer B.6 to obtain a Test Dilution having a concentration that is nominally equivalent to the median level of the standard. 

Acceptance criteria: 90.0%–125.0% 

4 SPECIFIC TESTS 

Sterility Tests 〈71〉: Meets the requirements 

Other Requirements: It meets the requirements for Particulate and Foreign Matter in Ophthalmic Products—Quality Tests 〈771〉, Drug Product Quality, Universal Tests, Particulate and Foreign Matter. 

5 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in collapsible ophthalmic ointment tubes. 

USP Reference Standards 〈11〉 

USP Chloramphenicol RS 

USP Polymyxin B Sulfate RS