Sodium Phosphates Compounded 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

Sodium Phosphates Compounded Injection contains NLT 95.0% and NMT 105.0% of the labeled amount of sodium and NLT 95.0% and NMT 105.0% of the labeled amount of phosphate. (USP 1-May-2022) It contains no bacteriostat or other preservative.

Prepare Sodium Phosphates Compounded Injection containing 3 mM/mL of phosphorus and 4.0 mEq/mL of sodium as follows (see Pharmaceutical Compounding—Sterile Preparations 〈797〉).

^a If anhydrous is not used, waters of hydration should be included in calculating the appropriate amount of sodium phosphates.

Dissolve the Dibasic Sodium Phosphate (anhydrous) in 50 mL of Sterile Water for Injection. Add and dissolve Monobasic Sodium Phosphate (anhydrous), and bring to final volume with Sterile Water for Injection. [Note—May need to heat to 77° to fully dissolve. If heating is required, allow to reach room temperature prior to passing through a filter.] Pass through a filter of 1.2-μm pore size to remove particulate matter, and sterilize by autoclave.

2 ASSAY

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Procedure for Sodium

Mobile phase: 8 mM methanesulfonic acid

Standard solution: 0.025 mg/mL of sodium prepared with USP Sodium Chloride RS and water

Sample solution: Transfer 0.07 (USP 1-May-2022) mL of Injection to a 250-mL (USP 1-May-2022) volumetric flask. Add approximately 200 mL of water and vortex for 30 s. (USP 1-May-2022) Dilute with water to volume and transfer to a polypropylene ion chromatography vial. (USP 1-May-2022)

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: Conductivity

Column: 4-mm (USP 1-May-2022) × 25-cm; packing L97

Column temperature: 30°

Flow rate: 1.0 mL/min

Injection volume: 10 μL

System suitability

Sample: Standard solution

[Note—The retention time for sodium is about 3.6 min.]

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0% for replicate injections

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of sodium (Na) in the portion of Injection taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of sodium from the Sample solution

r_S = peak response of sodium from the Standard solution

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

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

Acceptance criteria: 95.0%–105.0%

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Procedure for Phosphate

Mobile phase: 40 mM sodium hydroxide

Standard solution: 0.230 mg/mL of phosphate prepared from USP Dibasic Potassium Phosphate RS in water

Sample solution: Transfer 0.2 mL of Injection into a 250-mL volumetric flask. Add approximately 200 mL of water and vortex for 30 s. (USP 1-May-2022) Dilute with water to volume and transfer to a polypropylene ion chromatography vial. (USP 1-May-2022)

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: Conductivity

Column: 4-mm (USP 1-May-2022) × 25-cm; packing L103

Column temperature: 30°

Flow rate: 1.0 mL/min

Injection volume: 10 μL

System suitability

Sample: Standard solution

[Note—The retention time for phosphorus is about 5.4 min.]

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0% for replicate injections

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of phosphate (PO₄) in the portion of Injection taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of phosphate from the Sample solution

r_S = peak response of phosphate from the Standard solution

C_S = concentration of phosphate in the Standard solution (mg/mL)

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

Acceptance criteria: 95.0%–105.0%

3 SPECIFIC TESTS

pH 〈791〉: 5.3–6.3

Sterility Tests 〈71〉: Meets the requirements

Bacterial Endotoxins Test 〈85〉: NMT 1.10 USP Endotoxin Units/mg of sodium phosphates

Particulate Matter in Injections 〈788〉: Meets the requirements

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Package in single-dose glass containers. Store at controlled room temperature.

Beyond-Use Date: In the absence of passing a sterility test and endotoxins test, the storage conditions for high-risk compounded sterile preparations (CSPs) in Pharmaceutical Compounding—Sterile Preparations 〈797〉 apply. After successful completion of sterility and endotoxin testing, NMT 120 days after the date on which it was compounded when stored at controlled room temperature.

Labeling: Label it to state the Beyond-Use Date. The label states the sodium content in terms of milliequivalents in a given volume, and states also the phosphorus content in terms of millimoles in a given volume.

USP Reference Standards 〈11〉

USP Dibasic Potassium Phosphate RS

USP Sodium Chloride RS