Sulfadimethoxine Sodium

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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Sulfadimethoxine Sodium contains not less than 98.0 percent and not more than 102.0 percent of C12H13N4NaO4S, calculated on the dried basis.

1 Packaging and storage

Preserve in tight, light-resistant containers, and store at controlled room temperature.

2 Labeling

Label it to indicate that it is for veterinary use only.

USP Reference standards 〈11〉—

USP Sulfadimethoxine RS

Identification—

A: To about 100 mg, add 50 mL of water, mix until dissolved, and dilute with water to 100 mL. To about 5 mL of this solution add 100 mg of phenol, and heat to boiling. Cool the solution, and add 0.5 mL of sodium hypochlorite TS and 3 drops of 2.5 N sodium hydroxide: a yellow color is produced.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

C: Dissolve 10 mg in 2 mL of diluted hydrochloric acid, add 3 drops of sodium nitrite solution (1 in 100), and dilute with water to 4 mL: the solution turns yellow. Add 1 mL of 2.5 N sodium hydroxide containing 10 mg of 2-naphthol: a red-orange precipitate is formed.

pH 〈791〉: between 8.0 and 9.5, in a solution (1 in 20).

Loss on drying 〈731〉—Dry it at 125° for 3 hours: it loses not more than 5.0% of its weight.

3 Assay

Mobile phase, Standard preparation, and Chromatographic system—Proceed as directed in the Assay under Sulfadimethoxine.

Assay preparation—Transfer about 60 mg of Sulfadi methoxine Sodium, accurately weighed, to a 250-mL volumetric flask, add about 200 mL of Mobile phase, and swirl to dissolve. Dilute with Mobile phase to volume, and mix. Protect this solution from light.

Procedure—Proceed as directed in the Assay under Sulfadimethoxine. Calculate the quantity, in mg, of C12H13N4NaO4S in the portion of Sulfadimethoxine Sodium taken by the formula:

(332.31/310.34)(250C)(r_U/r_S)

in which 332.31 and 310.34 are the molecular weights of sulfadimethoxine sodium and sulfadimethoxine, respectively; and the other terms are as de fined therein.