Packaging and storage— Preserve in well-closed containers.

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

USP Reference standards á11ñ— USP Bacitracin Zinc RS.

pHá791ñ: between 8.0and 9.5,in a solution containing 25mg of specimen per mL.

Loss on drying á731ñ— Dry about 100mg,accurately weighed,in a capillary-stoppered bottle in vacuum at a pressure not exceeding 5mm of mercury at 60for 3hours:it loses not more than 8.5%of its weight.

Assay— Transfer an accurately weighed quantity of Soluble Bacitracin Methylene Disalicylate to a high-speed glass blender jar.Add 99.0mLof sodium bicarbonate solution (1in 50)and 1.0mLof polysorbate 80,and blend for about 3minutes.Proceed as directed for bacitracin under Antibiotics—Microbial Assays á81ñ,adding a sufficient volume of 0.01Nhydrochloric acid to an accurately measured volume of this solution so that the amount of hydrochloric acid in the Test Dilutionwill be the same as in the median dose level of the Standard,and quantitatively diluting with Buffer No.1to obtain a Test Dilutionhaving a concentration of bacitracin assumed to be equal to the median dose level of the Standard.

Expert Committee:(VET)Veterinary Drugs

USP28–NF23Page 215

Phone Number:1-301-816-8178