Sodium Phosphates Injection
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
Sodium Phosphates Injection is a sterile solution of Monobasic Sodium Phosphate and Dibasic Sodium Phosphate in Water for Injection. It contains not less than 95.0 percent and not more than 105.0 percent of the labeled amounts of monobasic sodium phosphate (NaH2PO4· H2O) and dibasic sodium phosphate (NaH2PO4· H2O). It contains no bacteriostat or other preservative.
Packaging and storage—Preserve in single-dose containers, preferably of Type I glass.
Labeling—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. Label the Injection to indicate that it is to be diluted to appropriate strength with water or other suitable fluid prior to administration and that once opened any unused portion is to be discarded. The label states also the total osmolar concentration in mOsmol per L. Where the contents are less than 100 mL, or where the label states that the Injection is not for direct injection but is to be diluted before use, the label alternatively may state the total osmolar concentration in mOsmol per mL.
Identification—It responds to the tests for Sodium 〈191〉 and for Phosphate 〈191〉.
Bacterial Endotoxins Test 〈85〉 —It contains not more than 1.10 USP Endotoxin Units per mg of sodium phosphates.
Particulate Matter in Injections 〈788〉: meets the requirements under small-volume injections.
Other requirements—It meets the requirements under Injections and Implanted Drug Products 〈1〉.
Assay for monobasic sodium phosphate—Transfer an accurately measured volume of Injection, equivalent to about 300 mg of anhydrous monobasic sodium phosphate, to a 100-mL beaker, and dilute with water to about 50 mL. Place the electrodes of a suitable pH meter in the solution, and titrate with 0.1 N sodium hydroxide VS to the inflection point to a pH of about 8.8. Each mL of 0.1 N sodium hydroxide is equivalent to 13.80 mg of NaH2PO4· H2O.
Assay for dibasic sodium phosphate—Transfer an accurately measured volume of Injection, equivalent to about 300 mg of anhydrous dibasic sodium phosphate, to a 100-mL beaker, and dilute with water to about 50 mL. Place the electrodes of a suitable pH meter in the solution, and titrate with 0.1 N hydrochloric acid VS to the inflection point to a pH of about 4.0. Each mL of 0.1 N hydrochloric acid is equivalent to 26.81 mg of NaH2PO4· H2O.
