Selenium Sulde Topical 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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» Selenium Sulfide Topical Suspension is an aqueous, stabilized suspension of Selenium Sulfide.

It contains NLT 90.0% and NMT 110.0% of the labeled amount of SeS₂.

It contains suitable buffering and dispersing agents.

[Note—Where labeled for use as a shampoo, it contains a detergent. Where labeled for other uses, it may contain a detergent.]

Packaging and storage— Preserve in tight containers.

1 Identification—

Digest about 2 g with 5 mL of nitric acid over gentle heat for 1 hour, dilute with water to about 50 mL, and filter:

the solution responds to Identification test A under Selenium Sulfide, when tested as directed, beginning with

“to 10 mL of the filtrate add 5 mL of water.”

pH 〈791〉:

Between 2.0 and 6.0.

2 Assay—

Place a portion of well-mixed Topical Suspension, equivalent to about 100 mg of Selenium sulfide and accurately weighed, in a suitable flask.

Cautiously digest with 25 mL of fuming nitric acid over gentle heat for 2 hours, and proceed as directed in the Assay under Selenium Sulfide, beginning with:

“Cool, transfer the solution to a 250-mL volumetric flask.”

Each mL of 0.05 N sodium thiosulfate is equivalent to 1.789 mg of SeS₂.

Where the Topical Suspension is labeled in terms of percentage (w/v) or of the amount of SeS₂ in a given volume of Topical Suspension, determine the density of the Topical Suspension as follows:

Using a tared, 100-mL volumetric flask, weigh 100 mL of Topical Suspension that previously has been shaken to ensure homogeneity, allowed to stand until the entrapped air rises, and finally inverted carefully just prior to transfer to the volumetric flask.

From the observed weight of 100 mL of the Topical Suspension, calculate the quantity of SeS₂ in each 100 mL.