Dexamethasone Sodium Phosphate Injection

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 Injection is a sterile solution of Dexamethasone Sodium Phosphate in Water for Injection. It contains NLT 90.0% and NMT 115.0% of the labeled amount of dexamethasone phosphate (C₂₂H₃₀FO₈P), present as the disodium salt.

2 IDENTIFICATION

2.1 A. THIN-LAYER CHROMATOGRAPHY

Solution A: Mix 3.1 g of boric acid and 500 mL of water in a 1-L volumetric flask. Add 21 mL of 1 N sodium hydroxide and 10 mL of 0.1 M magnesium chloride, and dilute with water to volume.

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: Pipet a volume of Injection, equivalent to 10 mg of dexamethasone phosphate, into a 100-mL volumetric flask, and dilute with water to volume. Pipet 5 mL of this solution into a 125-mL separator, and wash with two 10-mL portions of water-washed methylene chloride, discarding the washings. Transfer the solution to a glass-stoppered, 50-ml. tube, and add 5 mL of Solution B. Allow to stand at 37° for 45 min, and extract with 25 mL of methylene chloride. Evaporate 15 mL of the methylene chloride extract on a steam bath to dryness, and dissolve the residue in 1 mL of methylene chloride.

2.1.1 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)

2.1.2 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 R_F 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

Change to read:

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 Injection, in Mobile phase

3.1.1 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4-mm x 30-cm; packing L1

Flow rate: 1.6 mL/min

Injection volume: 20 µL

3.1.2 System suitability

Sample: Standard solution

[NOTE-The retention time for dexamethasone phosphate is about 5 min.]

3.1.3 Suitability requirements

Relative standard deviation: NMT 1.5%

3.1.4 Analysis

Samples: Standard solution and Sample solution

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

                Result = (r_U/r_S) x (C_S/C_U) × (M_r1/M_r2 ^▲_{▲(ERR 1-Feb-2023)}) × 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): 7.0-8.5

BACTERIAL ENDOTOXINS TEST (85): NMT 31.3 USP Endotoxin Units/mg of dexamethasone phosphate

OTHER REQUIREMENTS: Meets the requirements in Injections and Implanted Drug Products (1)

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in single-dose or multiple-dose containers, preferably of Type I glass, protected from light. Store at controlled room temperature.

USP REFERENCE STANDARDS (11)

USP Dexamethasone RS

USP Dexamethasone Sodium Phosphate RS