Packaging and storage— Preserve in tight containers.

Labeling— Label it to indicate that it is for veterinary use only.Label it to state the content of bacitracin in terms of grams per pound,each gram of bacitracin being equivalent to 42,000Bacitracin Units.

USP Reference standards á11ñ— USP Bacitracin Zinc RS.

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 5.0%of its weight.

Zinc content— Using Powder,proceed as directed for Zinc contentunder Bacitracin Zinc.Calculate the zinc content,in g,in relation to each 42,000Bacitracin Units in the specimen taken by the formula: in which Ais the bacitracin content of the specimen,in Bacitracin Units per g,and the other terms are as defined therein:it contains not more than 2.0g for each 42,000Bacitracin Units.

Assay— Dissolve an accurately weighed quantity of Powder quantitatively in 0.01Nhydrochloric acid to obtain a stock solution containing about 100Bacitracin Units per mL.Proceed as directed under Antibiotics—Microbial Assays á81ñ,using an accurately measured volume of this stock solution diluted quantitatively and stepwise with Buffer No.1to obtain a Test Dilutionhaving a concentration assumed to be equal to the median dose level of the Standard.In preparing each test dilution of the Standard,add additional hydrochloric acid to each to obtain the same concentration of hydrochloric acid as in the Test Dilution.

Expert Committee:(VET)Veterinary Drugs

USP28–NF23Page 216

Phone Number:1-301-816-8178