Thiostrepton

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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Thiostrepton is an antibacterial substance produced by the growth of strains of Streptomyces azureus (Fam. Streptomycetaceae). It has a potency of not less than 900 USP Thiostrepton Units per mg, calculated on the dried basis.

1 Packaging and storage

Preserve in tight containers.

2 Labeling

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

USP Reference standards 〈11〉—

USP Thiostrepton RS

Change to read:

Identification, Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020)

Loss on drying 〈731〉—Dry about 1 g of sample in vacuum at 60° for 3 hours: it loses not more than 5.0% of its weight.

Residue on ignition 〈281〉: not more than 1.0%.

3 Assay

Proceed as directed under Antibiotics—Microbial Assays 〈81〉, preparing the Test Dilution as follows. Transfer about 60 mg of

Thiostrepton, accurately weighed, to a beaker. Add about 125 mL of dimethyl sulfoxide, and stir with a magnetic stirrer until dissolved (about 5 minutes). Transfer this solution to a 200-mL volumetric flask, washing the beaker and the stirring bar with dimethyl sulfoxide. Add the washings to the volumetric flask, dilute with Dimethyl sulfoxide to volume, and mix. Dilute this solution quantitatively with dimethyl sulfoxide to obtain a

Test Dilution having a concentration of thiostrepton assumed to be equal to the median dose of the Standard.