Dexamethasone Sodium Phosphate Ophthalmic Solution

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

Dexamethasone Sodium Phosphate Ophthalmic Solution is a sterile, aqueous solution of Dexamethasone Sodium Phosphate. It contains an amount of dexamethasone sodium phosphate (C₂₂H₂₈FNa₂O₈P) equivalent to NLT 90.0% and NMT 115.0% of the labeled amount of dexamethasone phosphate (C₂₂H₃₀F₂O₈P).

2 IDENTIFICATION

2.1 A. Thin-Layer Chromatography

Solution A: Dissolve 3.1 g of boric acid, 203 mg of magnesium chloride, and 860 mg of sodium hydroxide in enough water to make 1000 mL.

Solution B: 1 mg/mL of alkaline phosphatase enzyme in Solution A

Standard solution: 300 µg/mL of USP Dexamethasone RS in methylene chloride

Sample solution: Transfer 5 mL of Solution B to a glass-stoppered, 50-mL tube containing 5 mL of the Sample solution from the Assay. Incubate at 37° for 45 min, then add 25 mL of methylene chloride and shake for 2 min. Evaporate 15 mL of the methylene chloride extract on a steam bath to dryness, and dissolve the residue in 1 mL of methylene chloride.

Chromatographic system

• (See Chromatography 〈621〉, Thin-Layer Chromatography.)
• Adsorbent: 0.25-mm layer of chromatographic silica gel mixture (20- × 20-cm plate)
• Application volume: 5 µL
• Developing solvent system: Chloroform, acetone, and water (50:50:1)
• Spray reagent: Dilute sulfuric acid (1 in 2)

Analysis

Samples: Standard solution and Sample solution

Allow the spots to dry, and develop the chromatogram using the Developing solvent system in a tank completely lined with filter paper until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing tank, mark the solvent front, and allow the spots to dry. Spray the plate with Spray reagent, and heat at 105° until brown or black spots appear.

Acceptance criteria: The Rf value of the principal spot of the Sample solution corresponds to that of the Standard solution.

2.2 B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 Procedure

Mobile phase: 0.01 M monobasic potassium phosphate in a mixture of methanol and water (1:1)

Standard solution: 0.09 mg/mL of freshly prepared USP Dexamethasone Sodium Phosphate RS in Mobile phase

Sample solution: Nominally 0.08 mg/mL of dexamethasone phosphate from Ophthalmic Solution in Mobile phase

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detector: UV 254 nm
• Column: 4-mm × 30-cm; packing L1
• Flow rate: 1.6 mL/min
• Injection volume: 20 µL

System suitability

• Sample: Standard solution
• [Note-The retention time for dexamethasone phosphate is about 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 (C₂₂H₃₀F₂O₈P) in the portion of Ophthalmic Solution 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 Dexamethasone Sodium Phosphate RS in the Standard solution (mg/mL)

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

M_r1 = molecular weight of dexamethasone phosphate, 472.44

M_r2 = molecular weight of dexamethasone sodium phosphate, 516.40

Acceptance criteria: 90.0%–115.0%

4 SPECIFIC TESTS

pH 〈791〉: 6.6–7.8

Sterility Tests 〈71〉: Meets the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers. Store between 15° and 25°.

USP Reference Standards 〈11〉

USP Dexamethasone RS

USP Dexamethasone Sodium Phosphate RS