Gentamicin 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

Gentamicin Sulfate Ophthalmic Ointment contains the equivalent of NLT 90.0% and NMT 135.0% of the labeled amount of gentamicin.

2 IDENTIFICATION

A. Thin-Layer Chromatography

Standard solution: 1 mg/mL of USP Gentamicin Sulfate RS in water

Sample solution: Nominally 1 mg/mL of gentamicin from Ophthalmic Ointment prepared as follows. Shake a quantity of Ophthalmic Ointment, containing nominally 5 mg of gentamicin, with a mixture of 200 mL of chloroform and 5 mL of water. Allow to separate, and filter the aqueous layer.

Chromatographic system

(See Chromatography 〈621〉, Thin-Layer Chromatography.)

Adsorbent: 0.25-mm layer of chromatographic silica gel

Application volume: 20 μL

Developing solvent system: Mix chloroform, methanol, and ammonium hydroxide (20:13:10). Allow to separate, and use the lower layer.

Analysis

Samples: Standard solution and Sample solution

Apply the Standard solution and the Sample solution to the plate. Place the plate in a chromatographic chamber, and develop the chromatogram in the Developing solvent system until the solvent front has moved three-fourths of the length of the plate. Remove the plate, air-dry, and expose it to vapors of iodine in a detection jar containing iodine crystals.

Acceptance criteria: The intensities and R values of the three principal spots of the Sample solution correspond to those of the Standard solution.

3 ASSAY

Procedure

(See Antibiotics—Microbial Assays 〈81〉.)

Sample solution: Shake a portion of Ophthalmic Ointment containing nominally 1 mg of gentamicin with about 50 mL of ether in a separator, and extract with four 20-mL portions of Buffer B.3 (see the chapter). Combine the buffer extracts, and dilute with Buffer B.3 to a suitable volume to obtain a Test Dilution with a gentamicin concentration that is nominally equivalent to the median level of the standard.

Analysis: Proceed as directed in the chapter.

Acceptance criteria: 90.0%–135.0%

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. Store at controlled room temperature.

USP Reference Standards 〈11〉

USP Gentamicin Sulfate RS