Neomycin and Polymyxin B Sulfates and Dexamethasone 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)

DOWNLOAD PDF HERE

1 DEFINITION

Neomycin and Polymyxin B Sulfates and Dexamethasone Ophthalmic Ointment contains the equivalent of NLT 90.0% and NMT 130.0% of the labeled amounts of neomycin and polymyxin B, and NLT 90.0% and NMT 110.0% of the labeled amount of dexamethasone (C₂₂H₂₉FO₅).

2 IDENTIFICATION

A. THIN-LAYER CHROMATOGRAPHIC IDENTIFICATION TEST (201BNP): Meets the requirements

B. The retention time of the dexamethasone peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay for Dexamethasone.

3 ASSAY

3.1 NEOMYCIN

(See Antibiotics-Microbial Assays (81),)

Sample solution: Shake a portion of Ophthalmic Ointment in a separator with 50 mL of ether. Extract with four 20-mL portions of Buffer B.3. Combine the aqueous extracts, and dilute with Buffer B.3 to a suitable volume.

Analysis: Proceed as directed in the chapter. Dilute the Sample solution with Buffer B.3 to obtain a Test Dilution having a neomycin concentration that is nominally equivalent to the median level of the standard.

Acceptance criteria: 90.0%-130.0%

3.2 POLYMYXIN B

(See Antibiotics-Microbial Assays (81).)

Sample solution: Shake a portion of Ophthalmic Ointment with 50 mL of ether in a separator. Extract with four 25-mL portions of Buffer B.6. Combine the aqueous extracts, and dilute with Buffer B.6 to a suitable 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 (10 polymyxin B units/mL). Add to each Test Dilution of the standard, a quantity of USP Neomycin Sulfate RS, dissolved in Buffer B.6, to obtain the same concentration of neomycin as in the Test Dilution of the sample.

Acceptance criteria: 90.0%-130.0%

3.3 DEXAMETHASONE

Mobile phase: Acetonitrile and water (1 in 3)

Diluent: Acetonitrile and methanol (1:1)

Standard solution: 60 µg/mL of USP Dexamethasone RS in Diluent

Sample solution: Nominally 60 µg/mL of dexamethasone from Ophthalmic Ointment in Diluent prepared as follows. Transfer a portion of Ophthalmic Ointment containing nominally 3 mg of dexamethasone to a suitable test tube, and add 15 mL of cyclohexane. Heat in a water bath at 75 ± 5° for 10 min. If the Ophthalmic Ointment is not fully dissolved, heat on a steam bath for about 30 s, place a cap on the test tube, and place on a vortex mixer until all solid material is dissolved. Pass with suction through a medium-porosity, sintered-glass filter. Rinse the test tube twice with 10-ml portions of cyclohexane, passing the rinsings through the filter, and discard the filtrate. Wash the filter with about 10 mL of a mixture of Diluent, and collect the filtrate in a 50-mL beaker. Wash the test tube and the filter with several 10-mL portions of Diluent, and combine the washings in the 50-mL beaker. Transfer the contents of the beaker to a 50-mL volumetric flask with the aid of Diluent, and dilute with Diluent to volume.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm x 25-cm; 5- to 10-um packing L1

Flow rate: 2 mL/min

Injection volume: 10 µL

System suitability

Sample: Standard solution

Suitability requirements

Relative standard deviation: NMT 1.5%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of dexamethasone (C₂₂H₂₉FO₅) in the portion of Ophthalmic Ointment taken:

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 Dexamethasone RS in the Standard solution (µg/mL)

C_u = nominal concentration of dexamethasone in the Sample solution (µg/mL)

Acceptance criteria: 90.0%–110.0%

4 SPECIFIC TESTS

STERILITY TESTS (71): Meets the requirements

OTHER REQUIREMENTS: It meets the requirements for Particulate and Foreign Matter and Container Contents in Ophthalmic Products-Quality Tests ( 771), Drug Product Quality, Universal Tests. Particulate and Foreign Matter and Container Contents

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in collapsible ophthalmic ointment tubes.

USP REFERENCE STANDARDS (11)

USP Dexamethasone RS

USP Neomycin Sulfate RS

USP Polymyxin B Sulfate RS