Neomycin Sulfate and Dexamethasone Sodium Phosphate 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

Neomycin Sulfate and Dexamethasone Sodium Phosphate Ophthalmic Ointment is a sterile ointment containing Neomycin Sulfate and Dexamethasone Sodium Phosphate. It contains the equivalent of NLT 90.0% and NMT 135.0% of the labeled amount of neomycin, and the equivalent of NLT 90.0% and NMT 110.0% of the labeled amount of dexamethasone phosphate (C₂₂H₃₀FO₈P).

[Note-Where Neomycin Sulfate and Dexamethasone Sodium Phosphate Ophthalmic Ointment is prescribed without reference to the quantity of neomycin or dexamethasone phosphate contained therein, a product containing 3.5 mg of neomycin and 0.5 mg of dexamethasone phosphate per g shall be dispensed.]

2 IDENTIFICATION

A. Thin-Layer Chromatographic Identification Test 〈201BNP〉: 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 for Dexamethasone Phosphate.

3 ASSAY

3.1 Neomycin

(See Antibiotics-Microbial Assays 〈81〉.)

Sample solution: Shake a weighed portion of Ophthalmic Ointment in a separator with about 50 mL of ether, and 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%–135.0%

3.2 Dexamethasone Phosphate

Buffer: 6.9 g/L of monobasic sodium phosphate

Mobile phase: Methanol and Buffer (52:48)

Diluent: Dissolve 0.29 g of dibasic sodium phosphate in 450 mL of water, and add 550 mL of alcohol.

Standard solution: 33 µg/mL of USP Dexamethasone Sodium Phosphate RS in Diluent. Prepare this solution freshly.

Sample solution: Nominally 30 µg/mL of dexamethasone phosphate, prepared as follows. Transfer a portion of Ophthalmic Ointment containing nominally 3 mg of dexamethasone phosphate to a suitable beaker. Add 65 mL of Diluent, and heat just to boiling. Pour the contents of the beaker into a separator containing 45 mL of isooctane. After shaking for 1 min, decant the lower layer into a 100-mL volumetric flask. Rinse the beaker with two 15-mL portions of Diluent, extracting the remaining isooctane in the separator with each portion, and decanting the lower layer from each extraction into the 100-mL volumetric flask. Dilute with Diluent to volume, and mix. Pass through a suitable filter.

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detector: UV 254 nm
• Column: 3.9-mm × 30-cm; 10-µm packing L1
• Flow rate: 1.5 mL/min
• Injection volume: 20 µL

System suitability

• Sample: Standard solution
• [Note-The retention time for dexamethasone phosphate is about 8.5 min.]
• Suitability requirements
• Relative standard deviation: NMT 1.5%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of dexamethasone phosphate (C₂₂H₃₀FO₈P) in the portion of Ophthalmic Ointment taken:

Result =(rᵤ/rₛ) × (Cₛ/Cᵤ) × (Mr₁/Mr₂) × 100

rᵤ = peak response from the Sample solution

rₛ = peak response from the Standard solution

Cₛ = concentration of USP Dexamethasone Sodium Phosphate RS in the Standard solution (µg/mL)

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

Mr₁ = molecular weight of dexamethasone phosphate, 472.44

Mr₂ = molecular weight of dexamethasone sodium phosphate, 516.40

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 Sodium Phosphate RS

USP Neomycin Sulfate RS