Sulfacetamide Sodium 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

Sulfacetamide Sodium Ophthalmic Ointment contains NLT 90.0% and NMT 110.0% of the labeled amount of sulfacetamide sodium (C₈H₉N₂NaO₃S · H₂O). It is sterile.

2 IDENTIFICATION

A. Sample: Nominally 1 g of sulfacetamide sodium from a quantity of Ophthalmic Ointment

Analysis: Dissolve the Sample in 100 mL of ether in a separator, and extract the mixture with 25 mL of water. Wash the extract with 25 mL of ether, and warm the water extract on a steam bath to remove the last traces of ether. Adjust with 6 N acetic acid to a pH of 4–5, and fIlter.

Wash the precipitate with water, and dry at 105° for 2 h. Use the precipitate in Identification B, C, and D.

Acceptance criteria: The sulfacetamide melts at 180°–184°.

B. Sample: 500 mg of the sulfacetamide from IdentificationA

Analysis: Place the Sample in a test tube, and heat gently until it boils.

Acceptance criteria: An oily liquid, which has the characteristic odor of acetamide, condenses on the walls of the test tube (distinction from the sublimates of sulfadiazine, sulfamerazine, and sulfamethazine, which are solids at room temperature).

C. Sample solution: 100 mg of the sulfacetamide from IdentificationA in 5 mL of water

Analysis: Add 5 drops of cupric sulfate TS to the Sample solution.

Acceptance criteria: A light bluish-green precipitate is formed, and it remains unchanged on standing.

D. Sample solution: 500 mg of the sulfacetamide from IdentificationA in 10 mL of dilute hydrochloric acid (1 in 10)

Analysis 1: To about one-half of the Sample solution add 2 mL of trinitrophenol TS.

Acceptance criteria 1: A very heavy occulent or almost gelatinous precipitate is formed.

Analysis 2: To the remainder of the Sample solution add 3 drops of formaldehyde TS.

Acceptance criteria 2: A white precipitate is formed, and it changes to orange on standing (distinction from sulfamethoxypyridazine).

3 ASSAY

Procedure

Diluent: 20% methanol

Mobile phase: Methanol, glacial acetic acid, and water (10:1:89)

Standard stock solution: 5 mg/mL of USP Sulfacetamide Sodium RS prepared as follows. Transfer 50 mg of USP Sulfacetamide Sodium RS to a 40-mL centrifuge tube. Add 10.0 mL of Diluent, insert the stopper, and mix using a vortex mixer for 3 min to dissolve the Reference Standard. Add 7.5 mL of heptane, insert the stopper, and mix using a vortex mixer for another 3 min. Centrifuge to effect separation of the phases. Withdraw, and discard the upper heptane layer.

Standard solution: 0.03 mg/mL of USP Sulfacetamide Sodium RS in Diluent from the Standard stock solution

System suitability solution: 0.03 mg/mL of sulfanilamide in the Standard solution

Sample stock solution: Nominally 5 mg/mL of sulfacetamide sodium prepared as follows. Transfer 100 mg of sulfacetamide sodium from a quantity of Ophthalmic Ointment to a 40-mL centrifuge tube. Add 15.0 mL of heptane, insert the stopper, and mix using a vortex mixer for 3 min to dissolve the Ophthalmic Ointment. Add 20.0 mL of Diluent, insert the stopper, and mix using a vortex mixer for 3 min. Centrifuge to effect separation of the phases. Withdraw, and discard the upper heptane layer.

Sample solution: Nominally 0.03 mg/mL of sulfacetamide sodium in Diluent from the Sample stock solution

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm × 25-cm; packing L1

Flow rate: 1.5 mL/min

Injection volume: 90 μL

System suitability

Samples: Standard solution and System suitability solution

Suitability requirements

Resolution: NLT 3 between the sulfacetamide and sulfanilamide peaks, System suitability solution

Column efficiency: NLT 1500 theoretical plates, determined from the analyte peak, Standard solution

Relative standard deviation: NMT 2.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of sulfacetamide sodium (C₈H₉N₂NaO₃S · H₂O) in the portion of Ophthalmic Ointment taken:

Result = (r_U/r_S) × (C_S/C_U) × (M_r1/M_r2) × 100

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

C_S = concentration of USP Sulfacetamide Sodium RS, calculated on the anhydrous basis, in the Standard solution (mg/mL)

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

M_r1 = molecular weight of sulfacetamide sodium monohydrate, 254.24

M_r2 = molecular weight of anhydrous sulfacetamide sodium, 236.23

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 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 Sulfacetamide Sodium RS