C72H85N19O18S5 1664.89[1393-48-2].

Packaging and storage— Preserve in tight containers.

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

USP Reference standards 11— USP Thiostrepton RS.

Identification, Infrared Absorption 197K.

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%.

Residual solvents 467: meets the requirements.

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.

Expert Committee : (VET05) Veterinary Drugs 05

USP29–NF24 Page 2134

Phone Number : 1-301-816-8178