Fluorescein Sodium Ophthalmic Strips

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

Fluorescein Sodium Ophthalmic Strips contain NLT 100.0% and NMT 160.0% of the labeled amount of fluorescein sodium (C₂₀H₁₀Na₂O₅).

2 IDENTIFICATION

A.

Sample solution: Cut the colored tip from 1 Ophthalmic Strip, place it in a small test tube containing 1 mL of water, and agitate for 1 min.

Acceptance criteria: Sample solution is strongly fluorescent, even in extreme dilution. The fluorescence disappears when the Sample solution is made acid and reappears when it is again made alkaline.

B.

Sample solution: Cut the colored tip from 1 Ophthalmic Strip, place it in a small test tube containing 1 mL of water, and agitate for 1 min. Place 1 drop of solution upon a piece of filter paper.

Acceptance criteria: A yellow spot is produced, and when exposed while moist to the vapor of bromine for 1 min and then to ammonia vapor, it becomes deep pink in color.

3 ASSAY

3.1 Procedure

Standard stock solution: 1 μg/mL of fluorescein sodium from USP Diacetyl fluorescein RS in water prepared as follows. Dissolve USP Diacetyl fluorescein RS in 10 mL of alcohol contained in a 100-mL volumetric flask, add 2 mL of 2.5 N sodium hydroxide, and heat on a steam bath at the boiling temperature for 20 min, with frequent swirling. Cool, and dilute with water to volume. Transfer a suitable aliquot to a volumetric flask, and dilute with water to volume. [Note—110.7 mg of anhydrous USP Diacetyl fluorescein RS is equivalent to 100.0 mg of fluorescein sodium.]

Standard solution: 0.03 μg/mL of fluorescein sodium in water prepared as follows. Transfer 3 mL of Standard stock solution to a 100-mL volumetric flask containing 20 mL of pH 9.0 alkaline borate buffer (see Reagents, Indicators, and Solutions—Buffer Solutions), and dilute with water to volume.

Sample stock solution: Remove 1 Ophthalmic Strip from its package, taking care not to allow any portion of the tip to adhere to the packaging material. Transfer to a 100-mL volumetric flask, add 50 mL of water, shake the flask vigorously, and dilute with water to volume.

Shake occasionally, and after 1 h, mix the contents of the flask. Transfer an aliquot (V) of this solution, equivalent to 100 μg of fluorescein sodium, to a 100-mL volumetric flask, and dilute with water to volume.

Sample solution: Transfer 3 mL of the Sample stock solution to a 100-mL volumetric flask containing 20 mL of pH 9.0 alkaline borate buffer (see Reagents, Indicators, and Solutions - Buffer Solutions), and dilute with water to volume.

3.2 Instrumental conditions

Mode: Fluorescence

Excitation wavelength: 485 nm

Emission wavelength: 515 nm

3.3 Analysis

Samples: Standard solution and Sample solution

Concomitantly determine the fluorescence intensities, I, of the Standard solution and the Sample solution.

Calculate the percentage of the labeled amount of fluorescein sodium (C₂₀H₁₀Na₂O₅) in the Ophthalmic Strip taken:

Result = (I_U/I_S) × (C_S/C_U) × 100

I_U = fluorescence value of the Sample solution

I_S = fluorescence value of the Standard solution

C_S = concentration of fluorescein sodium in the Standard solution (μg/mL)

C_U = nominal concentration of fluorescein sodium in the Sample solution (μg/mL)

Acceptance criteria: 100.0%–160.0% on the average content calculated from the individual assays of NLT 10 Ophthalmic Strips

4 PERFORMANCE TESTS

Content Uniformity: The content of fluorescein sodium (C₂₀H₁₀Na₂O₅) in each of NLT 10 Ophthalmic Strips, determined as directed in the Assay, is 85.0%–175.0% of the labeled amount.

5 SPECIFIC TESTS

Sterility Tests 〈71〉: Meet the requirements

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Package NMT 2 Ophthalmic Strips in a single-unit container in such a manner as to maintain sterility until the package is opened. Package individual packages in a second protective container.

Labeling: The label of the second protective container bears a statement that the contents may not be sterile if the individual package has been damaged or opened previously. The label states the amount of fluorescein sodium in each Ophthalmic Strip.

USP Reference Standards 〈11〉

USP Diacetyl fluorescein RS

Spiro(isobenzofuran-1(3H), 9'-(9H)xanthen)-3-one, 3',6'-bis(acetyloxy)-.

C₂₄H₁₆O₇ 416.39