Packaging and storage— Preserve in tight containers.

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

USP Reference standards 11— USP Nystatin RS. USP Neomycin Sulfate RS. USP Thiostrepton RS. USP Triamcinolone Acetonide RS.

Identification— Place 2 g of Cream in a conical flask, add 5.0 mL of chloroform, and shake for 10 minutes. Add 15 mL of alcohol, and shake for an additional 10 minutes. Filter the solution into a centrifuge tube, and evaporate the filtrate to dryness. Dissolve the residue in alcohol to obtain a solution containing about 250 µg of triamcinolone acetonide per mL. Proceed as directed in the Identification test under Triamcinolone Acetonide Cream, beginning with “Apply 10 µL of this solution”: the specified result is observed.

Minimum fill 755: meets the requirements.

Residual solvents 467: meets the requirements.

Assay for nystatin— Proceed as directed for nystatin under Antibiotics—Microbial Assays 81, blending a suitable, accurately weighed portion of Cream in a high-speed blender for 3 to 5 minutes with a sufficient, accurately measured volume of dimethylformamide to give a convenient concentration. Dilute an accurately measured volume of the solution so obtained quantitatively with dimethylformamide to obtain a stock solution containing about 400 USP Nystatin Units per mL. Dilute an accurately measured volume of this stock solution quantitatively with Buffer No. 6 to obtain a Test Dilution having a concentration of nystatin assumed to be equal to the median dose level of the Standard.

Assay for neomycin— Proceed as directed for the turbidimetric assay for neomycin under Antibiotics—Microbial Assays 81, placing an accurately weighed portion of Cream, equivalent to about 2.5 mg of neomycin, in a 250-mL conical flask, and treating it as follows. Add 50 mL of 0.01 N hydrochloric acid, and shake to disperse the Cream. Transfer the mixture to a 100-mL centrifuge tube. Wash the flask with 40 mL of hexanes, with shaking, and transfer the washing to the centrifuge tube. Stopper the centrifuge tube, shake, and centrifuge for 5 minutes. Draw off the lower aqueous layer, and transfer it to a 250-mL volumetric flask. Repeat the extraction of the hexanes layer remaining in the centrifuge tube with two 50-mL portions of 0.01 N hydrochloric acid, combining the aqueous extracts in the 250-mL volumetric flask. Dilute the contents of the volumetric flask with 0.01 N hydrochloric acid to volume, and mix. Dilute this solution quantitatively and stepwise with Buffer No. 3 to obtain a Test Dilution having a concentration assumed to be equal to the median dose of the Standard.

Assay for thiostrepton— Proceed as directed for thiostrepton under Antibiotics—Microbial Assays 81, blending a suitable, accurately weighed portion of Cream in a high-speed blender with a sufficient, accurately measured volume of dimethyl sulfoxide to give a convenient concentration, and filter. Dilute an accurately measured volume of the filtrate so obtained quantitatively with dimethyl sulfoxide to obtain a Test Dilution having a concentration of thiostrepton assumed to be equal to the median dose level of the Standard.

Assay for triamcinolone acetonide— Proceed with Cream as directed in the Assay under Triamcinolone Acetonide Cream.

Expert Committee : (VET05) Veterinary Drugs 05

USP29–NF24 Page 1570

Phone Number : 1-301-816-8178