Sulfadimethoxine Oral Suspension

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 Oral Suspension contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of sulfadimethoxine (C₁₂H₁₄N₄O₄S).

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

3 Identification

Shake a quantity equivalent to about 50 mg with 50 mL of water, and add 2.5 N sodium hydroxide dropwise until the solution becomes clear. Add diluted hydrochloric acid dropwise until a precipitate forms. Collect the precipitate on a very fine filter, and wash it with water and with ether: the sulfadimethoxine so obtained meets the requirements for the Identification tests under Sulfadimeth oxine.

pH 〈791〉: between 5.0 and 7.0.

4 Assay

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

Assay preparation—Transfer an accurately measured volume of Suspension, previously mixed and free from air bubbles, equivalent to about 50 mg of sulfadimethoxine, 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 sulfadimethoxine in each mL of the Oral Suspension taken by the formula:

250(C/V)(r_U/r_S)

in which V is the volume, in mL, of Oral Suspension taken to prepare the Assay preparation; and the other terms are as defined therein.