Sodium Nitroprusside for 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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Sodium Nitroprusside for Injection is Sodium Nitroprusside suitable for parenteral use. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of sodium nitroprusside (Na₂ [Fe(CN)₅NO] · 2H₂O).

Packaging and storage—Preserve as described in Packaging and Storage Requirements 〈659〉, Injection Packaging, Packaging for constitution.

USP Reference standards 〈11〉—

USP Sodium Nitroprusside RS

Constituted solution—At the time of use, it meets the requirements for Injections and Implanted Drug Products 〈1〉, Speciffic Tests, Completeness and clarity of solutions.

Identification—To 50 mg contained in a small test tube add 10 mL of ascorbic acid solution (1 in 50), and mix. Add 1 mL of dilute hydrochloric acid (1 in 10), mix, and add dropwise, while mixing, 1 to 2 mL of 1 N sodium hydroxide: a transient blue color is produced.

Bacterial Endotoxins Test 〈85〉 —It contains not more than 0.05 USP Endotoxin Unit per μg of sodium nitroprusside.

Water Determination, Method I 〈921〉: not more than 15.0%.

Other requirements—It responds to the Identification test A under Sodium Nitroprusside. It meets also the requirements for Sterility Tests 〈71〉,

Uniformity of Dosage Units 〈905〉, and Labeling 〈7〉, Labels and Labeling for Injectable Products.

Assay—

pH 7.1 buffer—Dissolve 1.36 g of monobasic potassium phosphate and 5.2 mL of a 1 in 4 solution of tetrabutylammonium hydroxide in methanol in water to make 1000 mL, and adjust with phosphoric acid or with the tetrabutylammonium hydroxide solution to a pH of 7.1.

Mobile phase—Prepare a suitable filtered mixture of pH 7.1 buffer and acetonitrile (about 70:30).

[Note—Use low-actinic glassware throughout the following sections.]

Standard preparation—Dissolve an accurately weighed quantity of USP Sodium Nitroprusside RS, in Mobile phase to obtain a solution having a known concentration of about 0.05 mg per mL.

Assay preparation 1 (where the label states only the total contents of the container)—Transfer the contents of 1 container of Sodium

Nitroprusside for Injection to a 100-mL volumetric flask with the aid of Mobile phase, dilute with Mobile phase to volume, and mix. Dilute an accurately measured volume of this solution quantitatively with Mobile phase to obtain a solution containing about 0.05 mg of Na₂ [Fe(CN)₅NO] · 2H₂O per mL.

Assay preparation 2 (where the label states the quantity of Na₂ [Fe(CN)₅NO] · 2H₂O in a given volume of constituted solution)—Constitute

Sodium Nitroprusside for Injection as directed in the labeling. Dilute an accurately measured volume of the constituted solution thus obtained quantitatively and stepwise with Mobile phase to obtain a solution containing about 0.05 mg of Na₂ [Fe(CN)₅NO] · 2H₂O per mL.

Chromatographic system (see Chromatography 〈621〉)—The liquid chromatograph is equipped with a 210-nm detector and a 3.9-mm × 30-cm column that contains 10-μm packing L11. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor for the analyte peak is not more than 2.0; and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure—Separately inject equal volumes (about 25 μL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of Na₂ [Fe(CN)₅NO] · 2H₂O in the container or in the portion of constituted solution taken by the formula:

L(C/D)(r_U/r_S)

in which L is the labeled quantity, in mg of Na₂ [Fe(CN)₅NO] · 2H₂O in the container, or in the volume of constituted solution taken; C is the concentration, in mg per mL, of USP Sodium Nitroprusside RS in the Standard preparation; D is the concentration, in mg of Na₂ [Fe(CN)₅NO] · 2H₂O per mL, of Assay preparation 1 or of Assay preparation 2, on the basis of the labeled quantity in the container, or in the volume of constituted solution taken, respectively, and the extent of dilution; and r_U and r_S are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.